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CHAPTER 01 PRINCIPLES OF PRESERVATION OF MEAT

Preservation : It is the process by which the freshness or acceptability properties of thefood are maintained.

Aim: 1.To inhibit microbial spoilage2. To minimize concomitant depreciation in meat quality.

No method of food preservation will improve the original quality of a food product

Principles of preservation of meat:

1. Prevention or delay of microbial decomposition

a. By keeping out micro-organisms (asepsis)b. By removal of micro organisms, e.g., by filtrationc. By hindering the growth and activity of micro-organisms, e.g., by low

temperature, drying, anaerobic conditions or chemicals.d. By killing the micro-organisms, e.g., by heat or radiations.

2. Prevention or delay of self-decomposition of food

a. By destruction or inactivation of food enzymes, e.g., by blanchingb. By delay of chemical reactions, e.g., by prevention of oxidation by means of

antioxidant.

3. Prevention of damage caused by insects, animals and mechanical causes.

Contributors of spoilage:

Microbes Bacteria, yeasts and moulds Action of enzymes that normally occur in meat calpain, cathepsin Others - Non enzymatic reactions in meat, such as oxidation, mechanical

damage such as bruising and damage from rodents and insects

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CHAPTER 02 SPOILAGE OF MEAT AND ITS DETECTION

Deterioration:

Abnormal changes in organoleptic qualities of food/meat

Categories of food deterioration:

PhysicalChemicalBiological

Factors that cause food deterioration include: light, cold, heat, oxygen, moisture,dryness, other types of radiation, enzymes, microorganisms, time, industrialcontaminants and macroorganisms (insects, mice, and so on).

Sources of contamination of meat :

(i) Hides, skin and feet of animals(ii) Instruments, knives, meat cutting equipments etc.(iii) Airborne contamination(iv) Water used for washing carcass(v) Meat handlers(vi) Storage, processing and transportation of meat and its environment

Factors affecting microbial growth on meat :

Two categories

a) Extrinsic factors b) Intrinsic factors

Those factors that can be controlled Those factors that are presentFrom outside. Intrinsically in meat

(i) Temperature (i) Water/ moisture(ii) Relative humidity (ii) P H

(iii) Availability of O 2 (iii) Oxidation Reduction potential(iv) Physical state of meat (or)(iv) Presence of nutrients(v) Presence or absence of inhibitory

Substances.

a) Extrinsic factors :

(i) Temperature :

Based on optimum temperature requirements bacteria are classified as

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(i) Psychrophilic - 45 0c

Meat is generally stored at a temperature of -1 to +3 oC where psychotrophs play a

major role in spoilage.

Critical temperature:

At 5 C where the growth of most of the psychotropic bacteria is reduced to certain leveland growth of all pathogenic organisms is stopped.

RH :

Meat is stored at a temperature of -1 to +3 oc and a RH of 88-92%. If RH is too high moisture condenses on the surface of meat resulting in sweating. If RH is too low,evaporation of surface moisture leading to dehydration and shrinkage.

Availability of O 2 :

Based on the requirement of O 2 for growth, bacteria are classified as

- Aerobic Pseudomonas sp ., yeast & moulds- Anaerobic Clostridium sp - Facultative anaerobes (i) micro aerobic (ii) micro anaerobic

Physical state of Meat:

- Carcass- Wholesale cuts - Retail cuts - Comminuted/ minced meat

Carcass has less contamination compared to wholesale and others becausecomminution/mincing/ cutting increases surface area for microbes to have contact andspoilage.

b) Intrinsic factors :Water :

Water is essential for the growth and multiplications of microbes. The amount of waterthat is available for microbes to grow is very important than the total water present inmeat.The amount of water that is available for microbial growth is called water activity(a w)

a w of pure water is 1.00Fresh meat is 0.99

Salt solution ( 22%Nacl) 0.86Saturated salt solution 0.75

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RH = a wx100, if a w of cooked meat is 0.99 then RH is 99%

P H :

Most bacterial population prefer pH near neutralMoulds P H required is 2-8 (generally prefer acid medium for growth)Yeasts P H of 4.0 to 4.8 is required for growth.

OR potential:

It indicates the oxidizing/ reducing power of meat

Aerobic organisms generally prefer a high OR potential (ie) highoxidizing activity.

Anaerobic organisms generally prefer a low OR potential.

Presence of nutrients:

Meat is an excellent and abundant source of nutrient for the growth of microbes.

Inhibitory substances: Meat has so such substances but some enzymes can.

Types of microbes in meat:

Gram - + ve Gram ve

Micrococcus sp. Pseudomonas spStreptococcus sp Achromobacter spStaphylococus sp Acinetobacter spLactobacillus sp Alcaligenes spLevconostoc sp Halo bacterium spBacillus sp Moraxella spClostridium sp Escherichia spMycobacterium sp Klebsiella sp

Molds Yeasts Aspergillus sp Candida spBotrytis sp Rhodotorula spFusarium sp Cryptococcus spThamnidium spSporotrichum spPenicillium sp

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Spoilage and decomposition of meat :

Spoilage :

It is the deteriorative (deleterious) change to the extent that meat or other food products

are unfit for human consumption.

Decomposition:

It is the process of break down of organic matter chiefly, the protein, Carbohydrates andlipids by the action of bacteria, molds or Yeasts.

When meat is decomposed, it is broken down to various chemical compounds, some ofwhich may be gaseous and very foul smelling.

Types of spoilage:

1. Microbial spoilage2. Enzymatic : (i) endogenous meat (ii) exogenous microbial3. Oxidation fatty oxidation4. Physical damage/changes

Microbial spoilage:

Surface spoilage:

Microbes produce slime on the surface of meat called sliminess, which is due to thecoalescence of the microbial colonies on the surface of meat.When microbial countcross/exceed log 7.5-8.0/cm 2 slime is noticed with off odour. Off-odour is noticed whenmicrobial load is log 7-7.5/cm 2. It is produced due to breakdown of variousproteinaceous compounds.

Presence of surface Carbohydrates and free amino acids support growth of microbesup to log 7.5 8.0/cm 2 like pseudomonas sp ; Alcaligenes sp, Flavobacterium sp ;

Coliforms

During growth, they utilize surface o 2 and create anaerobic environment

Anaerobes like clostridium sp. have favorable environment which invadedeep into the tissues.

Putrefaction

leads to breakdown of proteins

Proteoses

Peptides

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Amino acids

Indole, skatole, phenol

+Co 2 H2S, NH 3, CH 4

Putrefactive off odour

3. Oxidation:

Most common deleterious fatty changes in meat is called oxidative rancidity. Whenmeat is exposed to light and air (o 2), the USFAs present in the fatty tissues undergooxidation. Rate of oxidation depends on the degree of unsaturation.

Poly unsaturated fatty acids (PUFA) linoleic, linoleinc ,arachidonicMono unsaturated fatty acids (MUFA) oleic acid

Lipase enzymes are responsible for the lipolytic oxidation occurs in meat. Lipasebreakdown the fat by hydrolysis and produce the free fatty acids which gives rancidodour. The USFA s when they are subjected to oxidation they produce ketones andaldehydes gives rancid odour.

Physico-chemical changes in spoiled meat.

(i) change in colour from grey to greenish(ii) softening in the consistency of meat tissues(iii) A pronounced repulsive odour(iv) Alkaline reaction due to the production of NH 3

Heated beef/sour side

When the carcasses after dressing are stored very closely, there isless heat dissipation, which results in the growth of microbes on the surface of meatleading to sourness of meat. This can be prevented by leaving enough space between

carcasses. The same condition is called as green struck in rabbits, hares (or) game animals, when they are stored/stacked together.

Sulphiding/ Pseudomelanosis

it is seen in pork carcasses, due to delayed evisceration. Here, the kidney ( or)abdominal fat will have a greenish appearance. Kidney and liver will show a black spoton the surface. Black spots are due to the reaction of H 2 S from gut + Fe from Hb forming Fe 2S giving black color .

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Bone taint :

Occurs in hip joint of beef and pork carcass and occasionally in the shoulder region ofbeef.

Thick/ heavy muscled area like hip and shoulder of beef and pork+

Thick Fat cover

Delay cooling of meat during chilling process

Anaerobic bacteria from adjacent lymph nodes may proliferate in these joint

Produce taint / offensive odour due to decomposition of meat.

Prevention:

To prevent bone taint, avoid stress before slaughter. The internal temperature of muscleshould not exceed 4.5 0c after 48hrs of slaughter. Excess fat should be trimmed. Butcher

should make deep incision on the thick cuts to aid in aeration.Taints in hams/souringof pork in caused mainly by Clostridium sp

C. sporogenesC. PutrefaciensC. putreficum

Phosphorescence:

It is caused by pseudomones phosphorescence. It is seen in chilled meat when it isstored along with sea foods, as they are source of these bacteria. When the product isstored in dark, there is scattered luminous appearance on the surface of meat as if themeat surface is studded with stars. As soon as decomposition starts, phosphorescencewill disappear.

Spots :

(i) Red spots : on the surface of meat due to Serratia marcesens (ii) Blue spots : by Pseudomonas cyanogens (iii) Red mold : it is seen on a product called charque a salted dried meat of

south American countries due to Pseudomonas cutiruba

Moulds

They grow at low temperature also -7.5 to -8 0c

Black spot :

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most troublesome condition found in imported meat, due to Cladosporium herbarum . Inbeef found in neck, diaphragm, pleura. In lambs neck, inside of thighs, thoracic/abdominal cavities.

White spot :

It is found on the surface of hip, due to Sporotrichum sp & Chryosporium sp

Whiskers :

It is caused by Thamnidium & Mucor sp . It present on the meat surface & indicates thatmeat have been exposed to 0 C or above during storage

Bluish Green moulds : belong to pensicillum sp

Methods of detection of Meat spoilage :

Chemical methods:

a) Measurement of H 2S productionb) Measurement of mercaptans producedc) Determination of non-coagulable nitrogend) Determination of di- and tri methylaminese) Determination of tyrosine complexes; TBAf) Determination indole & skatoleg) Determination free amino acidsh) Determination volatile reducing substancesi) Determination biochemical oxygen demand (BOD)

j) Determination nitrate reductionk) Determination creatine contentl) Determination dye reducing capacitym) Measurement of total N 2 n) Measurement of catalaseo) Measurement of hypoxanthinep) Measurement of ATPq) Measurement of lactic acidr) Radiometric measurement of Co 2

s) Ethanol production ( fish spoilage)t) Change in color

Physical methods

a) Measurement of P H changes; surface tensionb) Measurement of refractive index of muscle juicesc) Measurement of UV illuminations ( fluorescence)d) Determination of alternation in electrical conductivitye) Determination of surface changesf) Determination of cryoscopic properties

g) Impedance changesh) Microcalorimetry

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Physicochemical methods

a) Determination of ERV

b) Determination WHCc) Determination of viscosityd) Determination of meat swelling capacity

Direct Bacteriological methods

a) Determination of total aerobesb) Determination of total anaerobesc) Determination of ratio of total aerobes to anaerobesd) Determination of one or more of above at different temperaturese) Determination of G-ve endotoxins Lal Test is done

Lal Limulus amebocyte lysate is an aqueous extract of blood cells (amebocyte) fromhorse shoe crab- limulus polyphemus . Lal reacts with bacterial endo toxin or lipopolysaccharide (LPS) used for the detection and quantifications of bacterial endotoxins

Organoleptic tests

Based on the senses of smell, touch and vision during spoilage.

Instrumental freshness tests

Chemilluminescene/chemoilluminescence:

Principle

When meat or fish undergoes spoilage, there is emission of light from USFA, and otherlipids which are measured by this instrument.

Torry meter ;

An instrument used to determine freshness of meat especially fish. It measures thechanges in the dielectric property of meat.

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CHAPTER 03 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -

TEMPERATURE CONTROL CHILLING AND FREEZING

Factors affecting preservation/spoilage of meat are:

1. Extrinsic factors - TemperatureHumidityO 2 supply

2. Intrinsic factors - Moisture/water content

Methods of preservation:

The various principles employed in preservation of meat are

Temperature control Moisture control Direct microbial inhibition

Food Thermometer:

Temperature control:

Temperature control

Cold preservation Thermal processing

Storing abovefreezing point

Storing belowfreezing point

Pasteurizationheat treatment -72-

75C(pasteurizedmeat products needlow temperaturestorage)

Sterilizationcommercial sterility

heat treatment - 100C

Refrigeration /cold preservation:

Storage above freezing point of meat/chilling:

It refers to storing the meat above the freezing point of meat i.e. -1 to -1.5 C, e.g., +5 Cor 0 - 2 C

Superchilling:

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The term super chilling is sometimes used of chilling to temperatures just above orbelow the freezing point, e.g., -2 C to +2 C

Quick chilling:

Quick chilling refers to a rapid lowering of carcase temperature starting not later than 1hour after slaughter and avoiding freezing.

Factors to be considered during refrigeration storage of meat are:

I. Characters of chilling room - Temperature Air speedRH

II. Carcass factors - Specific heat of the carcassSizeFat coverSpace between carcasses

Chilling Process: Chilling process can be arbitrarily divided into

I. Initial chilling processII. Terminal chilling processIII. Subsequent holding

Initial chill:

After completion of slaughter the internal temperature of animal carcass is between 30 -39 C so it must be removed to store the carcass. Pork, lamb veal carcasses are chilledin chill coolers at temperature between -1 C to 0 C. Poultry and fish are generally chilledby immersion in ice water. In general the temperature of carcasses should not be morethan 7 C offals not greater than 3 C. Air speed of the chill room should be 0.75m/s (toavoid cold shortening)

Factors affecting chilling rates are - Specific heat of carcass- Carcass size- Amount of external fat

- Temperature of chilling room- RH of chilling room- Number of carcasses- Space between carcasses

Beef:

In conventional chillers /coolers, beef carcasses usually require 48 hrs. of time to reachthe internal temperature of 5 C or less. Coolers with high velocity may decrease chillingtime by 35%. RH of chilling room is kept high to decrease excessive carcassesshrinkage due to moisture loss . Sufficient space between carcasses to assure rapidheat dissipation.

Poultry:

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Chilling is done by immersion in ice water. It is a rapid method of chilling. According toUSDA, internal muscle temperature should be decreased to less than 5 C or less within8 hrs of slaughter. This rapid chilling of hot carcasses of chicken and turkey causes acondition called cold shortening i.e when pre-rigor meat /carcass (before onset of rigor)

is chilled below 15-16C, there is severe contraction of muscles.

Contraction is caused by sudden release of ca ++ into the sarcoplasm andmay cause a physical shortening of 80% of original length of unrestrained muscles.Beef and lamb carcasses are more susceptible. To avoid cold shorting Electricalstimulation is done. ES accelerates glycolysis, proteolytic activity and cause physicaldisruption of muscle fibre.

Fish: Rapid chilling by ice water immersion

Final chilling/ terminal chilling and subsequent holding:

During terminal chilling, temperature of chill room is maintained between -1 to 3 C withair speed of 0.75m/s. During holding stage, meat/carcasses are maintained at atemperature of -1 to 3 C and air speed should be 0.5m/s and RH should be maintainedaround 90% (88 - 92%). After 12-24hrs of chilling, beef carcasses are removed fromchill coolers and placed (up to 7-10 days for conditioning) in holding room maintained at0 - 3 C until they are fabricated or shipped to users.

In case sheep carcasses initial chilling and holding cabinet are same asbeef. Pork carcasses after 24hrs of chilling are directly subjected to cutting operations.Chilling and holding rooms are maintained in dark condition to prevent light thataccelerates the oxidation of fat. Beef and sheep carcasses contain more saturated fattyacids whereas fish, poultry and pig carcasses contain more USFAs. These USFAs aremore prone for oxidative rancidity during chilling.

Factors affecting storage life under refrigeration are

- Initial microbial load- Temperature of storage- Humidity- Presence/absence of protective covering- Meat animal species- Type of product stored

Under ideal home refrigeration conditions the meat should be consumed within 4 daysof purchase after that freeze the meat.

Physical changes in chilled meat (effect of chilling):

1. Shrinkage: It is the loss of weight of meat/ carcass due to evaporation of surfacemoisture. Shrinkage is normally 1.5 - 2% but varies depending upon the storagecondition and carcass condition. If carcass cut into small pieces the surface areais increased results in increased shrinkage. The RH should be more to decreaseshrinkage (88-92%).

2. Sweating: when chilled meat is kept at room temperature, the water vapor getscondensed on the surface of meat where water droplets are seen.

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3. Loss of bloom: bloom is the attractive color and appearance of freshmeat/carcass when viewed through the semitransparent layer formed by the CT,fat and muscle, is called bloom. When surface of meat/carcass is moist, there isswelling of connective tissue due to absorption of moisture. So it become opaqueand gives a dull appearance. This is loss of bloom, which affects with

acceptability of meat. Loss of bloom is due to dehydration and oxidation of fat.Loss of bloom can be prevented by maintaining balance between temperature,air speed and RH.

4. Drying

Storage of meat below freezing point/freezing:

It is an excellent method of preservation of meat. It results in few undesirable changesin qualitative and organoceptic properties than other methods. Most of the nutritivevalue is retained.

Two factors that contribute to preservation of meat during freezing are

i) low available waterii) very low temperatures prevent the microbial growth

Very low temperature Inhibits metabolism and causes cold shock thus kills or inhibitsthe growth of the microbes.

Freezing rats:

- Freezing rates affect physical and chemical properties of meat

- Freezing rate is influenced by - Temperature of freezing medium- Movement of freezing medium- Packaging material used- Composition of meat products to be frozen.

Freezing methods:

Two methods of freezing are employedi. Slow freezingii. Quick freezing

Slow freezing:

It is also known as sharp freezing. In this method, the foods are placed in refrigeratedrooms at temperatures ranging from -4 C to -29 C. Freezing may require from 3 to 72hours under such conditions.

Quick freezing:

The lower temperatures used -32 C to -40 C freeze foods so rapidly that fine crystalsare formed and the time of freezing is greatly reduced over that required in sharp

freezing.

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Slow freezing Quick freezing

1.Temperature of the meat is reduced to -20 C in 3hrs to 72 hrs

1.Carcass temperature of -20 C isreached within 30 min.

2.Formation of large pleiomorphic icecrystals

2. Small, filamentous ice- crystals areformed that are not sharp.

3.Most of the ice-crystals are extra cellularin nature

3. Intracellular and extra cellular icecrystals are formed at the same rate andless opportunity for the ice- crystals togrow in size.

4.Huge quantity of drip loss 4.Very less or minimal drip loss

5. Due to long time of freezing microbesmay get adjusted to the temperature.

5.Due to fast freezing there is thermal/coldshock to microbes

6.More mechanical damage duringfreezing and refreezing

6. Mechanical damage is very less.

Different methods of freezing of meat:

1. Still air freezing2. Plate freezing3. Cold air blast freezing4. Liquid immersion and liquid spray5. Cryogenic freezing

1.Still air freezing:

Air is the medium of heat transfer. Heat exchange is by convection. Meat freezes veryslowly. Temperature in commercial still air freezers is -10 C to -30 C

2.Plate freezing:

Heat transfer medium is metal i.e. the metallic shelves kept in contact with freezer

plates i.e. product is pressed between the plates. Trays containing meat products orproduct itself are placed in direct contact with metal freezer plates Principle of heattransfer is by conduction. Temperature of plate freezer is maintained between -10 to -40 C. It is slightly faster than still air freezing. It is used for uniform rectangular packs orblocks.

3.Blast freezing:

It is the most common commercial method of freezing of meat and meat products. Air isthe medium of heat transfer. Temperature of blast freezers is -30 C to -40 C. Air speedof 5 m per sec (1000 ft per min) is maintained. Blast freezers will handle many shapes

and sizes and also batch and continuous operations.

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4.Cryogenic freezing / Liquid immersion & liquid sprays:

Most widely used commercial method for freezing poultry, especially turkeys. Packagedproduce is immersed in a tank or spray of refrigerant, normally calcium chloride orpropylene glycol solution is used as freezing liquid. When the surface of products are

frozen (crusted), the products are transferred to freezer room for subsequent frozenstorage. There are problems with leakage of refrigerant into packs. Cryogenic freezingutilizes very low temperatures to freeze product rapidly. Calcium chloride brine solutioncirculates from a tank through plate fin coils. These coils are above a stainless steel beltthat carries the meat product through a chamber. The moist product freezes instantly tothe belt as it makes contact and later pops off at the end where the belt turns under tobegin to return.

5.Liquefied gas:

Liquefied non toxic gas is sprayed in the vicinity of the product on a conveyor, etc;freezing occurs as the gas is vaporized. Liquid Nitrogen boils at -196 C. Liquid carbondioxide sublimes at -78 C. These two are widely used as cryogenic refrigerants incryogenic systems. Cryogenic spirulators have gained widespread acceptance in recentyears as a rapid freezing technique in the beef patty industry. The process is very rapid.The rapidly frozen foods may referred to as IQF (individually quick frozen). It is anexcellent method for small articles, e.g., chicken cut up parts or portions. With largeparticles there are problems surface cracking when the centre expands on freezing afterthe crust has set. This is relatively expensive method.

Physical and chemical changes in frozen meat (effect of freezing):

The freezing point of meat lies between -1 to -1.5 C; at -1.5 C, 35.5% of the musclewater is ice; at -5 C, 82% is ice; and at -10 C, 94% is ice. When the meat is frozenslowly the largest ice crystals are formed between the temperatures of -0.5 C and -4 C;this temperature range is known as the zone of maximum ice formation. Micro biologicalgrowth ceases at about -10 C but most of bacteria are resistant even at the lowest coldstorage temperatures. The microbiological quality of frozen food cannot be better than itwas before freezing.

1.Bone darkening:

This change occurs mostly in young chickens but rarely observed in ducks, geese,turkeys and old chickens. When young chickens especially fryers are thawed, themuscles adjacent to bones exhibit a bloody appearance in the uncooked state. Duringcooking the red color changes to dark grey or brown and in severe cases to black. Thisred color is due to Hb that has leached from marrow of relatively porous bones of youngchickens. During cooking the leached Hb is oxidized and converted to met Hb causingdark discoloration. Nutritive value, flavor and taste are not affected only appearance isaffected but it can be avoided by precooking at 70 C

2.Freezer burn:

Freezer burn is the result of sublimation of ice from unprotected surfaces of meat, etc.In the early stages there are small white spots or greyish areas sometimes called as

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freezer scorch and is caused by loss of moisture from the outer tissues. Thisdiscoloration disappear when the meat thaws out and the meat surface rehydrates. It isharmless but the appearance, eating quality is adversely affected. This can beprevented by using suitable packaging or cryogenic freezing.

3. Weeping or drip

Weeping denotes the presence of a watery, blood stained fluid which escapes fromfrozen meat when it is thawed and consists mainly of water, together with salts,extractives, protein and damaged blood corpuscles. It is an undesirable feature and iscaused partly by the rupture of the muscle cells and tissues by crystals of ice, and partlyby irreversible changes in the muscle plasm. The drip can be minimized if thawing isvery slow. The faster the meat is frozen, the lower the drip losses.

4.Thaw rigor:

Freezing the meat early in rigor or before rigor commences, when residual ATP is stillpres ent, leads to thaw rigor i.e. strong contraction with toughening when the meat isthawed. If the frozen meat is stored for long time, the ATP gradually disappears andthaw rigor diminishes. Freezing after rigor gives no special problems.

5.Durability of frozen meat

Frozen meat stored too long becomes dry, rancid and less palatable, the most importantchange being the breakdown of the fat into glycerine and free fatty acids, with theproduction of rancidity. The physical state of the muscle plasm (albumen and globulin)is considerably altered. They become insoluble and do not regain their solubility whenthe meat is thawed.

Effect of freezing on pathogenic micro organisms and parasites

Some bacteria are destroyed by freezing, but low temperatures merely inhibit thegrowth of the microbes. Anthrax bacilli can withstand a temperature of -130 C, whilesalmonella can withstand exposure to -175 C for three days, and tubercle bacilli canwithstand -10 C for 2 years, the virus of foot and mouth disease can remain viable for76 days. Freezing is however, a valuable method for the treatment of meat affected withcertain parasitic infestations. Pork affected with Cysticercus cellulosae can be rendered

safe if held for 4 days at -10.5

C to -8

C. Beef affected with Cysticercus bovis is killed bykeeping it for 3 weeks at -6.5 C or for 2 weeks at not more than -10.5 C. Trichinellacysts in pork are destroyed by holding the carcase for 10 days at -25 C.

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CHAPTER 04 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -TEMPERATURE CONTROL THERMAL PROCESSING

Thermal processing / heat processing

It involves pasteurization and sterilization and sometimes smoking

Sterilization:

Sterilization is the complete destruction or elimination of all viable organisms in/on afood product being sterilized. Sterilization destroys yeasts, molds, vegetative bacteria,and spore formers, and allows the food processor to store and distribute the products atambient temperatures, with extended shelf life.

Food substances become absolutely sterile only when no vegetative microorganisms orspores are present. Absolute sterility seldom exists in commercially canned products. Practically, complete sterilization will lead to deterioration in product quality andnutrients . Hence, in practice, commercial sterility is targeted.

Commercial sterility refers to the destruction of spoilage organisms and their sporessuch that a product will not undergo spoilage, even under indefinite storage period. Theproduct is being optimally processed so that under normal conditions, the product willneither spoil nor endanger the health of the consumer and also retain the organolepticproperties and nutrients.

The basic principles of sterilization technology as applied to food processing are :

1. The processed product must be free from microorganisms capable of producingfood-poisoning toxins and those microorganisms that cause food spoilage duringproduct shelf life, until it is consumed.

2. Clostridium botulinum spores are capable of growing in low-acid (pH>4.6)products during storage and hence must be heat treated to the equivalent of atleast 121.1C for 3 min (an F o value of 3) to achieve a 12-decimal reduction ofthe microorganism.

3. The processing conditions should be applied to the slowest-heating point referredto as cold point. This facilitates the assumption that, when the slowest heating

part is sterilized, by exposing it to the required time temperature profile, the restof the product will be sterilized.

Canning:

In commercial canning, carefully selected and prepared foods contained in apermanently sealed container are subjected to heat for a definite period of time andthen cooled. In most canning process, the heat destroys nearly all spoilage organismsand the permanent sealing of the container prevents infection. Canning is a veryeffective means of preservation. It destroys spoilage and pathogenic organisms.

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Thermal Death Time:

It is the shortest time necessary to kill a given number of organisms at a specifiedtemperature. By this method, the temperature is kept constant and the time necessaryto kill all cells is determined.

Determination of Thermal Death Time (Heat Resistant)

In order to decide a time and temperature combination to destroy an organism presentin food, it is necessary to know its heat resistance in that food which can be determinedby thermal death time (TDT) and its associated concepts. Thermal death time is thetime necessary to kill a given number of organisms at a specified temperature. By thismethod, the temperature is kept constant and the time required to kill all the cells isdetermined. The procedure for determining TDT is to place a known number of cells orspores in a sealed container such as a tube, can, capillary tube or a flask and thenexpose them to a specific temperature, in an oil bath for a required time period. At theend of the heating period, containers are removed and cooled quickly in cold water. Thecells or spores are removed and plated on the respective growth media to find out howmany of them have survived this heat process. The experiment is continued at the sametemperature by drawing samples at different time intervals and finding the survivors ineach sample by plate count. If you now plot the data as log number of survivors againsttime you get a straight line as shown in Fig. 4. The graph produced is called a survivorcurve, which is useful to calculate the D values for a spore or a vegetative cell.

Thermal death point:

It is the lowest temperature necessary to kill a given number of organisms in a fixedtime, usually 10 minutes.

D value:

This is the decimal reduction time, or the time required to destroy 90% of the organisms.The destruction of vegetative bacteria by heat is logarithmic and follows a first orderreaction.

D value is the decimal reduction time or the time required to kill 90% of the bacterialpopulation or the time in minutes required for the survivor curve to traverse one log

cycle as shown in Fig.

D values are frequently written with a subscript that defines the temperature, for

example, D 121 is the time required to kill 90% of a population of microorganisms at121C. D values are invaluable for comparing the relative heat resistance of organisms

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and calculating process times at a specific temperature. For example the most heatresistant spores of thermophilic bacteria, Bacillus stearothermophilus , have a D value at121C between 4.0-5.0 minutes compared to the D value of 0.01-0.07 for spores ofmesophilic bacteria, B. coagulans at the same temperature. Heat resistance ofmicroorganisms and their D values vary considerably which are given in table. Another

interesting feature during heat processing is the effect of increasing temperature on theD values. D value or the heat resistance of an organism decreases as the temperatureincreases. Therefore, you would expect to have a different D value at each temperature.Now if we determine the D values at different temperatures and plot them against theirtemperature on a semi-log paper, again we get a straight line that passes through logcycles as shown in Fig.

The graph produced is called thermal death time curve where each log cycle representsa z value. The z value refers to the temperature change (C) which results in a tenfold(1 log) decrease or increase in the D value. The z value provides information on therelative resistance of an organism to different destructive temperatures and can be usedto determine the equivalent D values at different temperatures. Supposing an organismhas a z of 15C and a D value of 5 minutes at 121C. We can use the z value to find theD value at any other temperature above its maximum growth temperature. If we raisethe temperature from 121 to 136C (121C + z value 15C), then the D value for theorganism is 0.5 minutes that is the one log cycle decrease in D value. Similarly if welower the temperature to 106C (121C - z value 15C), then D equals to 50 minutesthat is the one log cycle increase in D value. The z value can be calculated using thefollowing equation

z = (T2 T

1)/ (logD

1 logD

2)

Where D1

and D2

are the D values at temperatures T1

and T2

respectively.

The z values normally ranges from 5-8C for vegetative cells and 6-16C for spores ofbacteria.

F value / Farenheit value:

F value is the time in minutes required to destroy the spores / vegetative cells of aparticular organisms at 121 C. F Value represents, a measure of the ability of the heatprocess to reduce the number of spores or vegetative cells of a given organisms in acontainer.

Heating process is neither uniform nor instantaneous. In order to compare the lethal

effects of different processes, it is necessary for us to have some common currency todescribe them. One parameter is F value which is the time in minutes required to

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destroy the organism in a specified medium at 121C. The integrated lethal value ofheat received by all points in a container during processing is designated as F

sor F

o.

This represents a measure of the capacity of a heat process to reduce the number ofspores or vegetative cells of a given organism per container. F

omay be derived as

follows:

Fo

= D121

(log x log y)

Where x and y are the number of cells in the initial and the final population, respectively.For example, the widely accepted minimum lethality for a heat process applied to lowacid canned foods is that it should produce 12 decimal reductions in the number ofsurviving Cl. botulinum spores at 121C. This is known as the 12D concept orbotulinum cook or commercially sterile. If D

121of Cl. botulinum is 0.21 minutes then a

botulinum cook will have a Fo = 0.21(log1 log 10-12

) = 0.21 x 12 = 2.52 minutes. The

effect of applying a process with Fo to a product in which every can contains one sporeof Cl. botulinum (x = 1) will be that a spore will survive in one can out of every 10

12

thereby, making the product safe and stable at room temperature.Materials used for canning:

Containers for heat-preserved food must be hermetically sealed and airtight to avoidrecontamination from environmental microflora. Most of the thermally preservedproducts are kept in metal containers (cans), Others are packed in glass jars or plasticor aluminum/plastic laminated pouches.

Cans or Tins:Tinplate consists of steel plate which is electrolytically coated with tin on both sides. Thesteel body is usually 0.22 to 0.28mm in thickness (98.5% steel and 1.5% tin). The tinlayer is very thin (from 0.38 to 3.08 m). In addition, the interior of the cans is lined witha synthetic compound to prevent any chemical reaction of the tinplate with the enclosedfood. A phenolic meat lacquer / a sulphur resistant lacquer is used to avoid staining ofthe surface of certain food stuffs called sulphiding. An alternative method of avodingsulphiding is now being extensively used for meat packs and consists of chemicaltreatment of the inside of the can to form an invisible film, the solution used being astrong alkali bath containing phosphates and chromates.

Tin cans consist of two or three elements. In the case of three-piece steel cans, they arecomposed of the body and two ends (bottom and lid). The body is made of a thin steelstrip, the smaller ends of which are soldered together to a cylindrical shape. Two-piece steel cans have a lid similar to the three-piece cans but the bottom and body consist ofone piece, which is moulded from a circular flat piece of metal into a cup.

Aluminium is frequently used for smaller and easy-to-open cans. Aluminium cans areusually deep-drawn two-piece cans, i.e. the body and the bottom end are formed out ofone piece and only the top end is seamed on after the filling operation. The advantagesof aluminium cans compared to tin cans are their better deep-drawing capability, lowweight, resistance to corrosion, good thermal conductivity and easy recyclability. Theyare less rigid but more expensive than steel plate cans.

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Glass jars:

Glass jars are sometimes used for meat products but are not common due to theirfragility. They consist of a glass body and a metal lid. The seaming panel of the metal lid

has a lining of synthetic material. Glass lids on jars are fitted by means of a rubber ring.

Retortable pouches:

Retortable pouches which are containers made either of laminates of syntheticmaterials or laminates of aluminium foil with synthetic materials, are of growingimportance in thermal food preservation. Thermo-stabilized laminated food pouches,have a seal layer which is usually PP (polypropylene) or PP-PE (polyethylene) polymer,and the outside layers are usually made of polyester or nylon. From certain laminatedfilms, for instance, polyester / polyethylene (PETP/PE) or polyamide/polyethylene(PA/PE), relatively rigid containers can be made. The advantage of the retortablepouches/laminated containers is their good thermal conductivity which can considerablyreduce the required heat treatment time and hence is beneficial for the sensory productquality.

Canning:

Various steps involved in the canning process are

1. Selection and preparation of raw materials2. Blanching3. Filling of cans4. Exhausting/vacuumization5. Sealing of the container/closure6. Processing/sterilization/retorting7. Chilling8. Washing of cans9. External lacquering10. Labeling11. Storage/maturity

Selection and preparation of raw materials:

Meat should be handled hygienically and under strict temperature control so thatcontamination is avoided and the multiplication of microbes is prevented.The long term storage of meat intended for canning should be preserved under atemperature of -12C to 18C. A variety of process like grading, trimming, cutting,washing, canning, mincing are applied. Addition of emulsifiers and other supplementsshould be carried effectively and rapidly. Most of canned product are salted because itreduces the resistance of bacterial spores and thereby reducing cooking time.

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Blanching:

Products like meat, vegetables and fruits are selected or blanched in water at atemperature of 87C to 95C or exposed to steam.

Blanching is done to removal of respiratory gases which would reduce vacuum in thecan. It inhibits the enzymatic action which can reduce quality and nutritive value ofmeat. To Shrink of the product or to decrease in surface area and to clean the product.

Filling of the cans:

Filling of the cans is the critical part of canning process which can be done mechanicallyor by hand which should be done carefully. Two types of can filling1.hand filling2.mechanical filling

Hand filling:

Hand filling is geneally employed due to their configuration, for products which aresusceptible for damage during mechanical filling.

Mechanical filling:

It can be done by a wide variety of semi/fully automatic mechanical fillers. In mechanicalfilling, mostly commmunited products and products which have fine particle sizes arefilled in.

Exhausting:

It is an essential operations for the following reasons

Removal of air from the container before it is closed To prevent expansion of the contents during processing which may force the

seams. To remove the O2 which accelerates the intensive corrosion of the container. To create vacuum when the container is closed. Preventing the oxidation and preservation of Vit-C content

To produce concave ends so that any internal pressure may be detected and canbe rejected.

There are three methods of removal of air.

1.Heat exhaust2.Meachanical exhaust3.Steam injection

Heat exhaust:Contents of the can are filled cold and heated immediately before sealing. The effect is

to release air or gas trapped in the product.

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Mechanical/vacuumThe contents of the can filled cold and is sealed in a vacuum closing machine. A canbeing subjected to a vacuum during the seaming operations.

Steam injection:

This method involves injecting a blast of steam into the head space as the lid of the canis being positioned for sealing.

Sealing of the container :

A sealing of the can after evacuation is achieved by curling the edge of the lid over thecan containing a resilient sealing compound. The sealing material is often syntheticrubber compound must retain its resilience over the temperature range from below roomtemperature to above 130C. In modern can processing machine the sealing operation isabout a second. There are two sealing operations viz

1. Seaming operations2. Herematic seal operations

Processing and sterilization:

After exhausting and closing, the containers must be heated for an accuratelypredetermined time and temperature in an atmosphere of saturated steam in heatedwater or occasionally in an air steam mixture. The heat treatment takes place in retorts(Static/agitate) or in large hydrostatic retorts.

Except in aseptic canning the food is being processed in a hermetically sealedcontainer must be heated throughout by the conduction / convection of heat from anexternal heat source. High viscosity foods & solid foods such as meat and fish areheated by conduction.

A serious problem associated with conduction heating is time when smallvolumes of product at the can container sterilized, the peripheral portions are severelyover cooked. To avoid this, agitations during cooking and the presence of head spacenot only minimizes the uneven treatment but effectively the temperature and timerequired for safe processing. The agitation is achieved by rotational end-over-end oraxial movement of the retorts (cookers).

Canning in smaller retorts is called batch method. The sealing cans usually notmore than a few thousand per batch are manually loaded into the retort on trays or in

metal baskets. The cooking takes place under steam pressure. After cooking the steamis exhausted from the retort and the cans removed from cooking either by sinking themin water lands or spraying with water. This method requires considerable labour andoccupies very large space. To overcome this continuous lines able to handle hundredsof can per min are used today.

Cooling:

After the conclusion of heating process the cans are cooled as rapidly aspossible to avoid seam strain and thereby prevent over cooking of foods. The cansshould be cooled to an average temperature of 37C.

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External washing:

After cooling the sides of the cans become greasy. Hence washed with mild soap waterthen rinse with cold water. If surface of the cans is greasy external lacquering cannot bedone.

External lacquering:

It is done to prevent external corrosion. Commercial external lacquering is known asEnamel with a synthetic or vegetable resin.

Labeling:

Company nameDate of manufactureExpiry dateNutritional contents

Storage:

It can be stored at ambient temperature. All the cans are observed for 7-10days tocheck whether any change in the cans.

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CHAPTER 05 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -TEMPERATURE CONTROL HIGH PRESSURE PROCESSING

HPP is a non thermal and mild preservation technology that allows preservingthe natural characteristics of meat products to a high extent. But destroys pathogenicand spoilage micro organisms, the possible applications of HPP in meat processinginclude optimization of HPP conditions to inactivate target microorganisms for whichproduct and commercial presentation and to enhance the shelf life, development of newproducts based on cold jellification and coagulation of proteins pressure assistedfreezing and thawing , tenderization, improving the quality of pale , soft , exudative andDFD meats , post packaging intervention and meat separation. The most popularapplication of HPP are to produce pasteurized ready to eat meat, cooked and dry curedmeat products.

Basic principles of HPP:

During HPP the packaged food usually under vacuum in a flexible package isplaced in a pressure vessel containing a pressure transmitting liquid and submitted topressure ranging from 100-900 MPa. The pressure is produced by a hydraulic pump(indirect system) or by piston (direct system) and is isostatically transmitted inside thepressure vessel to the food product almost instaniously and uniformly. During highpressure applications pressure leads to increased ionization because water moleculesarrange more compact round electric charges. This results in more or less pronouncednegative and reversible Ph shifts dependent on the chemical nature of the food.

Effect of HPP on endogenous enzymes involved in meat quality:

Enzyme system responsible for muscle protein degradation or various exo andendo proteases. Inhibition of calpain activity by high pressure prevents the degradationof cytoskeletal proteins such as desmin, reducing the water holding capacity of musclei.e increasing the drip loss. The application of high pressure to fresh meat enhancesthe endogenous cathepsin and proteolytic activity involved in meat conditioning,probably due to the release of protease from lysosomes to the cytoplasm and bydenaturation of the tissue protein.

Effect of HPP on meat proteins and texture:

The HP treatment of pre-rigor meat for few minutes at 100 200 MPa inducesmeat tenderization. Further combined pressure heating treatments (150MPa 55 to60C, 30 min) are effective in contrasting cold shortening effects due to prerigorexcision combined with exposure to low temperatures. HP can affect molecularinteractions and protein conformation, leading to protein denaturation, aggregation orgelation.

Effect of HPP on lipid oxidation in meat and meat products

HPP promotes lipid oxidation in meat products. Catalysis of lipid oxidation seemsto take place during pressurization and has been related to the release of non-haem

iron and membrane damage. The effect of HPP on oxidative stability of lipids in meatdepends on applied pressure with a value between 300 400 MPa constituting the

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critical pressure to induce catalysis. Hence pressure induced oxidation may limit theusefulness of this technology for meat based products unless oxygen free packaging isused or antioxidants are added.

Effect of HPP on microbial inactivation:

The inactivation of micro organisms by HPP is the result of a combination of factorsincluding changes in the cell membranes, cell wall, proteins and enzyme mediatedcellular functions. The inactivation by HPP depends on the type of micro organisms andits growth phase, the pressure applied, pH and water activity. Gram negatives and cellsin growth phase are more sensitive than gram positives and cells in stationary phase.The cell death rate increases with increasing pressure but it does not follow first orderkinetics and a tail of inactivation is sometimes present. Pasteurization treatment in therange of 300 600 MPa for a short period of time inactivates the vegetative pathogenicand spoilage micro organisms ( 4 log units)

Regulatory aspects of HPP in meat processing:

USDS FSIS has issued a letter of no objection in 2003 for the use of HPP as aneffective post packaging intervention method in controlling Listeria monocytogenes inready to eat meat and poultry products for US companies. In the European communityHPP foods are classified as novel foods meaning equivalent to traditional food alreadyon the market.

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CHAPTER 06 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -MOISTURE CONTROL - DRYING

Preservation of Meat by Moisture control

Different foods are preserved by drying which is based on the fact that microorganismsand enzymes need water in order to be active. Air drying of muscle foods as a meansfor preservation has been practiced for centuries. Low moisture foods generally do notcontain more than 25% moisture and have an water activity

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Packing

Any dried product do not undergo micro bial spoilage but they undergo Chemical

spoilage e. g. of chemical spoilage is Maillard Reaction . The reaction occurs betweensugars and the carbonyl group of amino acids or proteins. This is also known as non-enzymatic browning. They develop a brown color and is bitter in taste.

To use This dried meat is put in water Rehydrated so that they absorb moisture andget proper taste and texture. Freeze dried meat has better rehydration capacitycompared to dehydrated meat.

2. Freeze drying / Cryophilization / lyophilization

Drying is done under frozen condition

Pre-Cooking

Freezing

Subjected to fast freezing(Very small ice ice crystals are formed)

Moved to drying chamberDrying is done under vacuum(1-1.5mmHg at T.C of 43 C)

The ice crystals are formed without forming water and are directly converted intovapour. This p rocess is called sublimation

Dried meats have a honey comb structure as crystals are vapourized and leave a

halo.

Moisture of AFD meat is

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1.Pronounced shrinkage of solids2.Migration of dissolved constituents to the surface when drying solids 3.Extensive denaturation of proteins 4.Case hardening : The formation of relatively hard, impervious layer at the surface of a

solid, caused by one or more of the first three changes that slows the rate of bothrehydration and reconstitution. 5.Formation of hard, impervious solids when drying liquid solution 6.Undesirable chemical reactions in heat-sensitive materials 7.Excessive loss of desirable volatile constituents 8.Difficulty of rehydration as a result of one or more changes.

3.Intermediate Moisture Foods:

Intermediate moisture foods are characterized by a moisture content of around 15-20%and the a W is between 0.60 and 0.85.

IMFs

Traditional IMFs New er/Developed IMFs Low a w are achieved by low a w of 0.60-0.85 is achieved

i. Absorption by addition of humeratants ii. Adsorptioniii. Additives like sugars and salts eg. Glycerols

eg; Dried fruit GlycolsFrozen food SortritolSugars, syrups SucroseCereals, honey SorbateJams, fruit juices

Water content is reduced to an extent such that, there is no available water for microbialspoilage, but maintains texture and eating quality of meat so that the meat can beconsumed without rehydration . The a W of meat is 0.99 and IMM s are having the a W -0.60-0.86. Staphylococcus aureus is the only bacterium of public health importance thatcan grow at a w values near 0.86, an IMF can be prepared by formulating the product sothat its moisture content is between 15 to 50% , adjusting the a W to a value below 0.86by the use of humectants and adding an antifungal gent to inhibit the yeast and moldwhich an capable of growing at a W values as above 0.70. Additional storage stability isachieved by 0.70pH

Preparation:

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Meat

Meat cubes (1cm3 )

Immersed in infusion solution( Immersion solution should be 11/2 times of meat)

Heated for 15 min at 70C

Kept in room temperature for equilibration for 15hrs at room temperature

Meat chunks are taken out and surface drying of meat pieces occurs

Packed in O 2, moisture impermeable packaging material.

Shelf life of Several months at room temperature.

Pet foods are also prepared by this method or by component blending.

Meat and meat products

Ground and mixed with liquid ingredients

Slurry is cooked/heat treated and later mixed with the dry ingredient( salt, sugar,dry solids and room)

Additional cook or heat process may be applied prior to extrusion and packaging

Extruded material may be shaped in the form of patties/ packaged in loose form

Pemmican:

- Is an adaptation of pemmican, an Indian trial and winter storage food made ofbuffalo meat and

- Pemmican is the name given to the chicken-based IMF.

Composition of Pemmican:

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Components Amount ( wt.basis%)

Raisins 30Water 23

Peanuts 15Chicken(freeze dried) 15NFDM 11Peanut, butter 4Honey 2

Humectants :

Humectants 15 commonly used in pet food manufacture are-Propylene glycol-Polyhydric alcohols(eg. Sorbitol)-Polyethylene glycols-Glycerol-Sugars( Sucrose, fructose, lactose, Glucose and corn syrup)-Salts ( Nacl,KCl,etc.)

Mycostats commonly used ones are- Propylene glycol- K-sorbate- Na-benzoate- The P H of these products may be as low as 5.4 and as high as 7.0

Infusion Solution:

High osmotic pressure solutions contain more solutes so two way infusion occurs.(i.e) Solutes enter meat and water comes out from meat so equilibration of wateractivity occurs.

10% Nacl0.5% antimycotic agent ( K-sorbate/Na-benzoate)33-40%-Propylene glycole/glycer.

The following general techniques are employed to change the water activity inproducing an IMF:i. Moist infusion: Solid food pieces are soaked and/or cooked in an appropriate

solution to give the final product the desired water level ( desorption).ii. Dry infusion: Solid food pieces are first dehydrated and then infused by

soaking in a solution containing the desired osmotic agents ( adsorption)iii. Component blending: all IMF components are weighed, blended, cooked and

extruded or other wise combined to give the finished product the desired a w. iv. Osmotic drying: foods are dehydrated by immersion in liquids with a water

activity lower than that of the food. When salts and sugars are used, twosimultaneous counter current flows develop; solute differs from solution into

food, and water diffuses out of food into solution.

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CHAPTER 07 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -MOISTURE CONTROL - CURING

Curing

Modern meat curing is the application of salt, nitrate or nitrite ions, seasonings andother additives to meat to develop unique properties and resistance to rapiddeterioration.

Meat Curing ingredients:

Meat curing ingredients are salt, nitrite, several reductants, alkaline phosphatesand seasonings. Two main ingredient must be used for curing are salt & nitrite andother above said ingredients are added to accelerate curing, stabilize color, modifyflavor & texture and reduces shrinkage during processing .

a) Salt :

- It included in all meat-curing formulas.- It functions to solubilize proteins and develop desirable flavor.- It acts as a dehydrating agent, osmotically lowering the water content of the

product and bacterial organisms thus limiting their ability to thrive and reproduce.

b) Nitrate / Nitrite : (either as potassium/sodium salt)

- Used to preserve desired meaty flavor- Retards lipid oxidation thus prevent warmed over flavor(WOF)- To fix the characteristic bright reddish pink color in cured meat- Nitrate is converted to nitrite by microbes or by a reducing agent ascorbate.- Nitrite is the active meat curing agent. It prevents Botulism and has bacteriostatic

property.

Both nitrite and nitrate are toxic to humans when consumed at levels higherthan allowed in cured meat products.

c) Reductants: (compounds capable of donating electrons)

- Added in meat product to accelerate color development- Nitrate must be reduced to nitric oxide and ferric ions of muscle pigments must

be reduced ferrous ions before proper color development occurs.- Most commonly used reductants are sodium salt of ascorbic acid or iso

ascorbic (erythorbic) acid- Ascorbate commonly known as Vitamin C inhibits the formation of

nitrosamines(cancer causing agents) in cured meats.

d) Alkaline phosphates (food grade):

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- No direct role in the curing reaction- To decrease the shrinkage in cured and smoked meat products- They increase the water-binding capacity of meat and reduce shrinkage during

subsequent processing.

- Phosphates also retard development of oxidative rancidity and may improvetexture.

- The phosphates approved for use are disodium phosphate, monosodiumphosphate, sodium meta phosphate, sodium poly phosphate, sodium tripolyphosphate, sodium pyro phosphate, sodium acid pyro phosphate, dipottasiumphosphate, mono potassium phosphate, potassium tri poly phosphate, potassiumpyro phosphate

e) Sugars

- A secondary ingredient in the curing formula, counteracts the astringent quality ofthe salt

- It enhances the flavor of the product- Provides the substrate for the formation of acid, thus lowering the pH of the cure- Sugar enhances the growth of micro organisms that reduce the nitrate to nitrite- Most frequently used sugars are sucrose and dextrose

f) Seasonings:

- Seasonings like spices, herbs, vegetables, and sweeteners are oftenincorporated with curing ingredients.

- They do not enter the curing reaction but do impart flavors. - Spices commonly used in seasoning various meats are pepper, cinnamon, clove,

nutmeg.

Methods for incorporation of cure ingredients:

- Several techniques are used, but proper distribution of cure ingredients thoughtthe entire product is necessary

- Improper distribution of cure ingredients results in poor color developmentBone sour in hams & gray areas in the inside of other products are examplesof problems from improper distribution of the cure mixtures.

a) Dry curingImmersion curing

b) Pickle curing Artery pumping

Injection curing stitch pumping

Multiple stitch pumping

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a) Dry curing :

- Curing ingredients are rubbed in dry form over cut surfaces- The cuts are then placed in refrigeration on shelves or in containers and allowed

to cure.

- For large cuts such as hams, cure should be applied more than once during thecuring period and the cuts must be over hauled, turned over & restacked.

- Since dry cure is slow (cure penetration is about 2.5cm/wk) and requires largeamount of hand labor and hence it is now used only on specialty items such as Country cured hams and bacons.

b) Pickle curing :

Pickle curing is curing of meat and meat products immersed in a solution composedof curing ingredients dissolved in water (pickle).

(i) Immersion curing:

- Widely used in the preparation of smoked meat products.- The cuts (meat) are immersed in the pickle solution- It is a slow method of curing, since extended periods are required for the pickle to

diffuse through the entire product.- Only specialty products like neck bones, tails, pigs feet and salt pork are cured in

this manner.

(ii) Injection curing:

- Injection if the pickle solution directly into the meat to shorten the produce ofcuring is called injection curing.

- Injection curing may be performed by several methods

(i) Artery pumping(ii) Stitch pumping(iii) Multiple stitch pumping

i) Artery pumping :

- Pickle solution is directly pumped into the vascular system ( arteries)- Artery pumping requires utmost care not to rupture the arteries with excessivepumping pressure.

- Mostly used in curing of hams.

ii) Stitch pumping

- Very popular method used on any type of meat cut- Pickle is injected through a hollow needle into various parts of the cut, especially

the thickest parts and near the joints.

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iii) Multiple stitch pumping :

- It is a variation of stitch pumping- Pickle is injected simultaneously and automatically through a series of hollow

needles.

Diffusion and binding of pickle in the meat cuts depend on the mechanical forcessuch a s tumbling/massaging. Tumbling and massaging means subjecting theproducts to agitation, which helps disrupt tissue structure and hasten distribution ofcure ingredients.

- Massaged smoked meat product have higher yields because of improved waterbinding capacity.

- They are more tender because of hydrated state of proteins and loss of structuralintegrity.

Chemistry of cured meat color

One purpose of curing of meat is to develop as attractive stable color and for this thechemistry of color fixation is highly important.

Nitrates & Nitrites are the principal compounds used in curing of meat and products toobtain the cured meat color.

NO 3 to NO 2 : If nitrate is used in the mixture, it should be first converted to nitrite, whichis in turn reduced to nitric oxide.

Nitrate

Nitrite

Reduced heatMyoglobin (+) Nitric oxide Nitric oxide Nitrosyl

Myoglobin processing haemochromogen

(Basic reaction occurring during color development)

Nitrate ( No 3-)

Nitrate reducing bacteria

Nitrite ( No 2-)

Nitric oxide

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- Mostly nitrite is used in commercial curing mixtures to eliminate the process fornitrate reduction and for rapid color development.

- Nitrate is used less and less usually only on long cured products

Deoxymyoglobin( purplish red ) Fe 2+

Oxygenation Oxymyoglobin(brightred ) Fe 2+

DeoxygenationHeat

Oxidation Nitric ReductionOxide

Reduction Oxygenation

OxidationHemo chrome(greenish brownto grayish

pink)Fe 2+

Nitric oxidemyoglobin( red) Fe 2+

( nitrite) Metmyo globin( brown) Fe 3+

ProteinDenaturation Oxidation

(heat)Reduction

Light

Oxidation Nitric Oxide + reduction

Formation of cured meat pigment

Nitric OxideMet myoglobin(brown) Fe 3+

Hemi chrome ( or)Denatured Metmyoglobin( brown) Fe 3+

NitrosylHaemochromogen(pink) Fe 2+

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Since nitrite is a very efficient oxidizing agent for myoglobin, the initial reaction isprobably the conversion of myoglobin and oxymyoglobin to metmyoglobin.

Nitric oxide then combines with the heme portion of the metmyoglobin to produce

nitric oxide met Mb

Nitric oxide Met Mb must be reduced to NO. Mb ( desired pigment) It involvesaddition of an e - with to Fe3+ of heme, converting it to Fe2+, natural reduction isslow, hence ascorbates speed up the reduction, by donating e - to ferric state ( Fe3+)of the heme. Use of reductants reduce the time for cured meat color developmentfrom several days to several hours.

The final reaction is formation of Nitrosyl hemochromogen. It involves denaturationof the protein portion of the myoglobin, leaving the heme structure intact with nitricoxide. The denturation is caused by the heat in cooking process.

The color of the denatured pigment ( Nitrosyl hemochromogen is more stable thanthat of the native pigment. Nitrosyl hemochromogens is a heat stable pigment anddoes not undergo further color change upon additional cooking of cured products.

Excessive amounts of nitrite in cured also may cause a greening of cured meatpigment called nitrite burn due to oxidation of cured meat pigment. It is common infermented sausages & pickled pigs feet since nitrite is highly reactive in an acidenvironment, nitrite burn is common in fermented s ausages & pickled pigs feets as they are high in acidity.

Public health aspects of nitrite usage

- Nitrite is toxic if consumed in excessive amounts single dose of 15 - 20 mg/kgBodyweight is lethal.

- Nitrite acts as the source of carcinogenic compounds known as nitrosamines - residual level of 200ppm of nitrite has been adopted as safe.- 40 - 80ppm- nitrite has been adopted as the minimum level required to inhibit

clostridium botulinum spores in meat products- Nitrite react with amines (secondary amines NR 2H) to form nitrosamines.

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CHAPTER 08 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -MOISTURE CONTROL - SMOKING

Smoking of meat:

Hot smoking (82C)

Cold smoking (43C)

Smoke is generally produced by slow combustion of saw dust derived from hardwoods(consisting of about 40-60% cellulose, 20-30% hemicelluloses, 20-30% lignin) smokeinhibits microbial growth, retards fat oxidation, imparts flavour to cured meat. Traditionalmethods of smoking are un controlled process, simply burning the wood beneath themeat. Conventional/advanced smoking method the process is done in a controlled

environment. Speed of smoke deposition, humidity, temperature maintained preciselyby electronic systems so consistent quality in smoked meats can be obtained.

Composition of wood smoke

Composition of wood smoke is a complex, but it may consists of two phases

A dispense, liquid phase containing smoke particles

A dispensing gas phase

Direct deposition of smoke particles makes a negligible contribution to the process butvapour absorption by surface and interstitial water is much more important.

Alcohol eg. Methanol least important possesses mild wood alcohol (or) bactericidaleffect

Organic acids

vapour phase Formic, Acetic, Propionic, butyric, isobutyric

Particulate phase - valeric, isovaleric, caproic, caprylic, capric

Minor preservative action, coagulation of the surface protein enhanced by acids therebyproducing good skin in frankfurters. Vanillic acid is responsible for a sweet, mellow notein the aroma of wood smoke.

Carbonyls

Acetone, propanal, Furfural, carbonyls in the vapour phase of smoke react with aminogroups on the surface of food this is known as maillard reaction resulting in colour andflavour development.

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Colour development directly related to smoke concentration and the moisture contenton surface of meat (12 15% moisture on surface resulting in many colourdevelopment). Formaldehyde Bactericidal effect

Phenols

Guiaiacol, 4 methyl guiaiacol, 2-6- dimethylphenol Most effective phenoliccompound in wood smoke imparting flavour. It has antioxidant and bacterio staticproperty primarily on the surface only.

Polygelic hydrocarbons

Benzpyrene, dibenz (a,b), anthracene etc.

(3,4 Benzpyrene) (1,2,5,6 phenanthracene)

Car cinogenic compounds in smoke both the compounds are formed from lignin

Gases

Co 2, Co, O 2 (Nitrous oxide + secondary amines Nitrosamine)

To prevent formation of N Nitrosamines erythrbate and Ascorbate added) Action of smoke

Phenols & poly phenols reacts with sulphydryl groups of the proteins.

Carbonyl groups reacts with amino groups resulting in flavour and colour development.Both reaction reduces the available aas especially lysine.

Antioxidant property helps to stabilize the fat soluble vitamins.

Wood consists of 60% cellulose, 20-30% hemicelluloses, 20-30% lignin. At thetemperature 590F or above lignin is decomposed yields phenol & its derivatives,

The best quantity smoke is produced at combustion temperature of 650 - 750 F and atan oxidation temperature of 390 - 480 F)

Combustion temperature at 750 F are desirable for maximum production of phenols butalso favours formation of benzpyrene.

To minimize the production of carcinogenic substances a more practical temperature of650 F is applied.

The Nature of smoke

Vapour phase more volatile components responsible for characteristic flavour &aroma

Particulate phase having undesirable polycyclic hydrocarbons & tars.

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Methods of Application of smoke

Smoke houses

Traditional old style country smoke houses had little or no control of temperature,

humidity or rate of combustion.

Modern smoke houses are of three types

Natural air circulation

Air conditioned or forced air

Continuous

Natural air circulation

This type is designed so that natural ventilation will occur. Regulation of volume of air iscontrolled by the opening or closing of a series of dampers thus providing naturalcirculation.

Air conditioned/forced ventilation

This type of smoke houses permits much more precise control of smoking. Aircirculation is controlled by a fan, so the air can be recirculated, exhausted. Thus thistype smoke houses gives uniform air movement and good control of temperature.

Continuous smoke houseThe continuous smoke house comprises part at the continuous processing system andis developed specifically for frankfurter production. It occupies less space and also hasmuch low labour requirement per unit of finished product. The continuous smokingsystem permits better control of shrinkage more specific control of processing time,temperature, RH. The smoking section of the continuous processing line must beequipped with supplemental smoke generators to allow cleaning and repair withoutshutting down the line.

Liquid smoke An alternative to natural, manufactured from burning wood under commercial conditionsuch that selected volatile consistuents can be recovered from the smoke andconcentrated in a liquid form. Liquid smoke is added to the brine or applied as a dippolishing or sprayed on the product

Advantages

Installation of smoke generator is not required

Composition of liquid smoke is constant

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CHAPTER 09 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -DIRECT MICROBIAL INHIBITION - IRRADIATION

DIRECT MICROBIAL INHIBITION

Preservation of meat foods by direct microbial inhibition includes the use of thefollowing.

Ionizing radiationChemical preservatives

Antibiotics.

Food irradiation is a technology for controlling spoilage and eliminating foodbornepathogens. The result is similar to pasteurization. The fundamental difference betweenfood irradiation and pasteurization is the source of the energy used to destroy themicrobes. While conventional pasteurization relies on heat, irradiation relies on theenergy of ionizing radiation.

Food irradiation is a process in which approved foods are exposed to radiant energy,including gamma rays, electron beams, and x-rays. Irradiation is not a substitute forgood sanitation and process control in meat and poultry plants. It is an added layer ofsafety. Radiation may be defined as the emission and the propagation of energythrough space or through a material medium.

The type of radiation of primary interest in food preservation is electromagnetic. Thevarious radiations are separated on the basis of wavelengths, with shorter wavelengthsbeing most damaging to microorganisms.

The electromagnetic spectrum may be further divided as follows with respect to theseradiations of interest in food preservation viz.

Micro wavesUV raysX-raysGamma rays

EM radiation is divided into ionizing and non ionizing radiation

Ionizing radiationSurface pasteurizationElectronic pasteurizationE-beam sterilization/pasteurization

When radiation strikes other material, it transfers energy. This can cause heating, aswith microwave cooking, or if there is enough energy, it can knock electrons out of the

material bombarded, breaking the molecular structure-thus leaving ions (free radicals)hence the name ionizing radiation.

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EMR :

Ionising:

Ionizing radiations are the primary interest in food preservation. Radiations having thewavelength of 2000A or less is commonly used.

Alpha particlesBeta -raysGamma raysX rays

Cosmic rays

Non Ionising:

UVIRMicrowaves

Their quanta contain energy to ionize molecules in their paths since they destroy microorganisms without appreciably raising temperature, the process is termed as Coldsterilization.

Units of radiation:

Roentgen: is a unit of measure used for expressing exposure dose of x-ray or gammaradiation

Milliroentgen : is equal to 1/1000 of a roentgen.

Curie : curie is a quantity of radioactive substance in which 3.7x10 10 radioactivedisintegrations occur per second.

1 g. of pure radium possess the radio activity of 1 curie of radium. The new unit for curieis the Becquerel.Rad : is the basic unit of radiation. It is defined as being equivalent to the absorption of

100 ergs per gram of matter.Kilorad:1 kilard ( krad) is = 1000 rads1 mega ( Mrad) is = 1million rads

Gray:Newer unit of absorbed dose is the gray.1 Gray=100 rads = 11joule per Kg; 1kGy = 105 rads;1 eV: The energy gained by an electron in moving through 1 volt is designated as ev (electron volt).meV : A meV is equal to 1 million electron volts. Both the rad and ev are measurements

of the intensity of radiation.

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Characteristics and types of Radiation of interest in food preservation

Ultraviolet light ( UV light):

Powerful bactericidal agent. It is non-ionizing and is absorbed by proteins and nucleic

acids, leading to photochemical changes that cause cell death. Cell death is caused bylethal mutations on nucleic acids. Since UV light has poor penetration ability, it is verylimited in food applications, where it catalyses oxidative changes that lead to rancidity,discolorations and other reactions.

Beta rays :

Beta rays may be defined as a stream of electrons emitted from radioactive substancesCathode rays are similar, except that they are emitted from the cathode of an evacuatedtube. It has poor penetration power. Linear accelerators are among the commercialsources of cathode rays.

Gamma raysThese are EMR emitted from the exited nucleus of elements such as 60Co and 137 Cs two radio nucleotides often used in food preservation due to their low cost/cheapestform of radiation.( as they by-products of atomic fission or atomic waste products)Excellent penetration powerT1/2 of 60Co 5yrs, T 1/2 of 137 Cs 30yrs.

Disadvantage :Radio active source emits radiation in all directions, hence permanent shielding toprotect environment & workers is necessary. Radio nucleotides cannot be turned ononly when needed. High cost and safety concerns associated with disposal.

X- raysThese are produced by the bombardment of heavy- metal layers with high-velocityelectrons (cathode rays) within an evacuated tube. They are essentially the same asgamma rays in other aspects.

AdvantagesGreater flexibility. Mono directional characteristicEase with which an electron accelerator can be turned off.

Possibility to transport the radiation source without massive radiation shields.Microwaves :

When electrically neutral foods are placed in an EM field, the charged asymmetricmolecules are driven first one way and then another. During this process, eachasymmetric molecule attempts to align itself with the rapidly changing alternating currentfield. As the molecules oscillate about their axes while attempting to go to the properpositive and negative pole, inter molecular friction is created and manifested as aheating effect. Most food research had been carried out at two frequencies i.e 915 and2450 megacycles. At the microwave frequency of 915 megacycles, the molecules

oscillate back and forth 915 million times /sec.

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Principles underlying the destruction of micro organisms by irradiation:

Types of organismsNumbers of organismsComposition of suspending men-strum (food)

Presence or absence of oxygenPhysical state of food

Age of organisms

Types of organisms:

G +ve bacteria are most resistant to irradiation than G-ve.Spore formers are more resistant than non-spore formers with several exceptions

Among spore-formers Bacillus larvae seems to possess high degree of resistance thanmost aerobic spore formersSpores of Clostridium botulinum type A appear to be the most resi stant of all Clostridialspores

Apart from the seven extremely resistant species Enterococcus faecium R53,micrococci and homo fermentative lactobacilli are among the resistant of non-sporeforming bacteriaMost sensitive to radiation are the Pseudomonads & flavobacters

No. of organisms:

The numbers of organisms have the same effect on the efficacy of radiations as in thecase of heat, chemical disinfection, and certain other phenomena. The larger thenumber of cells, the less effective in a given dose.

Composition of suspending men-strum (food)

Microbes in general are more sensitive to radiation when suspended in buffer solutionsthan in protein containing media.Eg; D-values for a strain of Cl.perfringens to be 0.28 in phosphate buffer, while incooked meat both the d-value is 3kGyProteins exert a protective effect against radiations as well as against certainantimicrobial chemicals and heat.Presence of nitrites tends to make bacterial endospores more sensitive to radiation.

Presence or absence of oxygen :

The radiation resistances of microbes is greater in the absence of oxygen then in itspresence. Sulphydryl compounds also increase the radiation resistance like anerobicenvironment.

Physical state of food :

Radiation resistance of dried cells are higher than moist cells.

Radiation resistance of frozen cells are greater than non-frozen cells.

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Age of organisms:Bacteria in its lag phase just prior to active cell division are more resistantLog phase most sensitive.

Sources of ionizing radiation:

Gamma sources of irradiationX-ray machinesElectron acceleratorsGamma RaysEnergy comes from decay of radioactive isotopesCobalt-60 (half life of 5.3 years) & Produced by neutron bombardmentCesium-137 (half life of 30 years) & By-product of spent nuclear fuel

Application of Radiation:

The most widely used techniques of irradiating food are gamma radiation fromeither Co 80 and Cs 137 and the use of electron beams from linear accelerator.

Rad appertization, Radicidation and Radurization of foods:

In 1964 an International group of microbiologists suggested the followingterminology for radiation treatment of foods.

Rad appertization:

Equivalent to radiation sterilization or commercial sterility of canned foods. Typicallevels of irradiation are 30-40 kGY.(or) 3-4 Mrad. The effect of this treatment onendospores and exotoxins of Cl. Botolinum is of obvious interest. Among Type A,B,D,Espores type E most radiation sensitive.

Radicidation:

Equivalent to pasteurization of product such as milk. It refers to a reduction in thenumber of specific viable non-spore forming pathogens, other than viruses, so that noneis detectable by any standard method. Typical level to achieve this process are 2.5-10kGY.

Radurization :

It is a lower level of pasteurization that is used to reduce specific spoilage microorganisms. It refers to the enhancement of the keeping quality of a food by causingsubstantial reduction in the number of viable specific spoilage microbes by radiation.The Dose range is 0.1 to 0.5 Mrad ( 1-5 kGY). Common dose levels are 0.75 to 2.5 kGYfor fresh meat, poultry, seafood, fruits vegetables and cereal grains.The minimum radiation dose(MRD) in kGy for the radappertization of meat products are

Bacon 23

Beef 47Chicken 45

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Pakistan & Brazil adopted codex alimentarious standard that any f ood may beirradiated to any doseNASA is authorized to sterilize frozen meat for astronauts at doses of 44 kGY as anotable exception.

At least 20 different food packing materials have been approved by the US food & drug

administration (FDA) at levels of 10 to 60 kGY.

1983- FDA permitted spices & vegetables seasonings to be irradiated up to 10kGY.

1985 FDA granted permission to irradiate pork up to 1kGY to control Trichinellaspiralis. Min 0.03 Mrad ( 0.3kGY), Max 0.1 Mrad ( 1kGY)

WHO has given approved for radiation dosages up to 7.0 kGY ( 0.7 Mrad)

Effect of Irradiation on Food quality:

The undesirable changes that occur in certain irradiated foods may be caused directlyby irradiation or indirectly as a result of post irradiation reactions. Water undergoesradiolysis when irradiated in the following manner:

3H 2o ----------- radiolysis ----------- H+OH+H 2o2+H2

In addition, free radicals are formed along the path of the primary electron and reactwith each other as diffusion occurs. Some of the products formed along the trackescape and react with solute molecules.

The main drawbacks of the application of irradiation of foods are color changes and/orthe production of off-odours and off-flavours. Raw fresh meats and cured meats turnbrown. Cooked fresh meat turns pink upon irradiation in the absence of 0 2.

Off odours when beef irradiated with levels on the order of 4 Mrad (40kGY) sulfurousodour predominate. Beyond 4-10 Mrad an odour descri bed as wet dog odour (or) wet -dog hair odour (due to S-containing carbonyl compounds is most noticeable. Anaerobicirradiation- minimize off-flavors & odours (i.e) irradiate at sub-freezing temperatures toreduce or halt radiolysis and to limit the mobility of its consequent reactants. Other thanwater, proteins, other nitrogenous substances in foods appear to be most sensitive toirradiation effect. Among the aas most sensitive are aromatic aas methionine,

cysteine, histidine, arginine, tyrosine. Irradiation of lipids and fats results in theproduction of carbonyls and other oxidation products such as peroxides Products ofirradiation are NH 3, H2 , CO 2, H 2S amides & carbonyls .

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CHAPTER 10 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -DIRECT MICROBIAL INHIBITION CHEMICAL PRESERVATIVES

Chemical preservatives:

Large number of chemicals have been described that show potential as foodpreservatives, only a relatively small number are allowed in food products due to strictlegal standards and limitations.

Nitrites, nitrites and sulfur dioxides are most commonly used in meat products.Nitrates - 500ppmNitrites - 200ppmSO 2 - 450ppm

According to FDA ( Food & Drug Administration, USA) certain chemicals are designatedas GRAS ( Generally Recognized as safe) and are permitted to the used in meat food.Those chemical preservative are given below

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CHAPTER 11 HURDLE CONCEPT - METHODS OF PRESERVATION OF MEAT -DIRECT MICROBIAL INHIBITION - ANTIBIOTICS

Antibiotics :

Antibiotics are secondary metabolites produced by microorganism that inhibit or kill awide spectrum of other microorganisms.Eg; Tetracyclines etc.

Bacteriocins are chemical compounds produced by microorganism that inhibit or killother microorganisms, but, unlike antibiotics, they inhibit or kill only closely relatedspecies or different strains of the same species.

Nisin :It acts on most G+ve bacteria. It is produced by Lactococcus lactis strains, polypeptidenature, Most widely used antibiotic for food preservation, prevent spoilage of swisscheese by C.botulinum, prevent the outgrowth of C. botulinum spores, for canning oflow- acid foods F 0 value of 6-8 is required to inactivate C. botullinum endospores butNisin + canning F 0 value is reduced to 3. Based on country standards & foods 2.5 to100ppm is used

Natamycin ( antifungal) :It is called as pimaricin/tennecetin/myprozine. It is a polyene by chemical natureEffective against yeasts and molds and not bacteria. It is isolated from Streptomycesnatalensis. Mechanism bind to membrane sterols and inducing distortion of selectivemembrane permeability Since bacteria has no membrane sterols, no action on bacteriais evinced.

Tetracyclines :Chortetracylines (CTC) and Oxytetr acyclines (OTC) were approved by FDA in 1955 &1956 respectively, at a level of 7ppm to control bacterial spoilage in un cookedrefrigerated poultry. CTC is more effective than OTC. 7 to 10mg is permitted in foods.Later they are banned as they are used in various disease treatments.

SubtilinThis antibiotic was discovered and developed by scientists at the western RegionalLaboratory of the USDA. Structurally similar to Nisin, produced by some strains ofBacillus subtilis, effective against G +ve bacteria, effective in canned food at levels of 5-20ppm in preventing the out growth of endospores ,mode of action same as Nisin

Tylosin :It is a non-polyene macrolide antibioticMore inhibitory than nisin/subtilin.More effective on G +ve bacteria.Inhibits protein synthesis by associating with the 50S ribosomal subunits.

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CHAPTER 12 PROCESSED MEATS BASIC MEAT PROCESSING PRINCIPLES

Processed muscle foods :

Diversity is one of the many desirable characteristics of processed muscle food.Processed muscle food are convenient, versatile and whole some and contributepositively to the diet by providing an excelle