PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING Reducing the free-water Drying Salting ...

93

Transcript of PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING Reducing the free-water Drying Salting ...

Page 1: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.
Page 2: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

PRESERVATION OF FISH AND AQUATIC PRODUCTS II

2

Page 3: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

PRESERVING

Reducing the free-water Drying

Salting

Smoking

Chemical means Fermentation

Pickling

3

Page 4: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

DRYING

Removal of water from fish (to reduce water activity) to extend shelf life

Requires input of heat (evaporate water) Sun, wind, flame, electrical etc.

Requires removal of water in the form of vapor

4

Page 5: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

DRYING PROCESS

5

Center HeatSurfacemoistureevaporates

Morewater

Lesswater

Water diffusion

Morewatervapor

Lesswatervapor

Page 6: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

DRYING PRINCIPLES

Drying occurs in two phases Phase 1 (constant rate period)

Water removed from surface

Phase 2 (falling rate period) Water is removed from muscle

Water migrates to the surface (diffusion)

Water evaporates at surface (requires heat)

Water is removed from the atmosphere surrounding the fish surface

6

Page 7: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

7

Page 8: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

8

Page 9: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

9

Page 10: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

10

Page 11: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

11

Advanced automated driers

Page 12: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Problems with dried fish If environmental T is warm and fish is too wet

Molds (Aw>0.75) Grow very well when drying in tropical areas

Aerobic spoilage bacteria (if non-salted)

If salted (solar salt) can get halophiles growing Pink colonies Major problem with salted and dried cod

Pests Insect parts and eggs a major quality problem Flies (Dipteria) lay eggs and can spread disease

Less problem with fish pre-drying Salting can deter flies Some use insecticides on fish!

Rodents and birds are a constant problem

12

Page 13: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Problems with dried fish (cont.) Lipid oxidation (rancidity)

Protein denaturation Get muscle fragmentation

If drying is too rapid we can get “case hardening”: water-impermeable skin at the surface

Case hardening Flesh soft on the inside and spoiled by bacteria (extreme putrid

odor)

13

Page 14: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

SALTING

Salting - traditional method

Reduces water activity (aw) to retard microbial spoilage and chemical reactions

Salt penetrates into the muscle and binds the water.

At 6-10% in the meat will spoilage

14

Page 15: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Different grades of salt, from 80-99.9% purity Purer salt leads to less problems

less contaminants (less water uptake, bitterness)

less halophilic bacteria (salt tolerant)

Some salts can have up to 105 of bacteria

At least 95% purity should be used Impure salts about 80% NaCl

Solar salt most impure (major source of halophiles)

Can purify by washing briefly with water (calcium and magnesium dissolve sooner than NaCl)

Finer salts are ideal for brines (dissolve rapidly) Larger size salt preferred during dry salting

15

Page 16: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

16

Fish in saturated salt brine at 0.75

Page 17: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

17

Page 18: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Methods of salting

Brine salting (15-25% solution) Fish immersed in solution of salt

Frequent stirring necessary

Replacement of salt in brine may be needed

Need to supply fresh brine to new batch of fish

Dry salting (3-4 parts fish to 1 part salt) Salt rubbed into fish surface and fish left uncovered to dry

Not recommended in tropical regions due to insects and rodents

18

Page 19: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Methods of salting (cont.) Kench salting

Salt rubbed on split fish and stacked. Pickle formed which leaks away

Pickle salting Same as above but pickle is not removed. Fish are packed in water

tight containers

Pickle is from water and blood leaking from the muscle as salt penetrates

Need about 30% salt for this to occur

Salt brine injection Fish injected with salt solution and phosphates, then soaked in salt

solution for 2 days (10 C=50 F) and then kench salted

19

Page 20: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

20

Mackerel being dry-salted

Page 21: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Head, gut and wash fish

Soak in 10% brine for 30 min

Drain

Dry salt fish in shallow boxes

Stack fish up first one skin down, last one skin up

Leave for about 12 h (or up to 30 days)

Wash salt crystals away with 10% brine or seawater

Dry fish during day

Pile fish up overnight

Pack product21

Process example (salted groundfish):

Page 22: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

22

Typical cod salting operation (kench salting)

Splitting the cod

Page 23: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

23

Salting the cod

Page 24: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

24

Maturation period in salt

Page 25: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

25

Drying the cod

Page 26: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

26

Drying fish the old way (still widely done)

Page 27: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

27

Quality inspection and packaging

Page 28: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

28

Injection

Page 29: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

29

Distributing the fish

Page 30: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

30

2 day soaking period in salt

Page 31: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

31

Fillet sorting/grading and packaging

Page 32: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

32

Pickle salting

Early stagesLate stages

Page 33: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Factors influencing the salting process Thickness -> thicker = slower NaCl uptake Fat content -> more = slower NaCl uptake Quality -> older = faster NaCl uptake Salt concentration and quality Temperature

More rapid salt penetration at higher temps

More chance of spoilage (normally in center of fish, turns into a smelly paste)

Storage Keep cool, dry and well ventilated Have plenty of insect/rodent traps The saltier the product the longer the shelf-life

33

Page 34: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

34

Page 35: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

35

Smoking

Old preservation method.In developed countries, used for flavor and color

Flavors

Water

Smoke(Hot air)

Page 36: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

PREPARATION

Start with good quality seafood.

Whole, headed, gutted, split, fillets, chunks,

Salting

Brine (2-5%), spices, sugar

Air drying (a few hours)

36

Page 37: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

PREPPING

Page 38: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

BRINING

Page 39: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

DRY BRINING

Page 40: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

RACKING

Page 41: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

INTO THE SMOKER

Page 42: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FINISHED!

Page 43: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

SMOKING TEMPERATURE

1. Cold smoking

Room temperature (<90 F)

Not cooked

Perishable product

2. Hot smoking

Temperature (>150 F)

Cooked

43

Page 44: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

LIQUID SMOKESmoke is absorbed by a liquid, and concentrated.

Rapid, uniform, but different than “real” smoke

44

Page 45: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

NATURE OF SMOKEMixture of particles and vapors.

1. Vapors

More than 200 chemicals

Carbonyls, organic acids, phenols, organic bases, alcohols, hydrocarbons, others.

Impart color and flavor enhancement

45

Page 46: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

VAPORSAntioxidants: high boiling phenols

Smoldering fire is better

Bactericidal: formaldehyde, acetic acid, creosote.

Also heat, drying, salt.

Reduces bacteria, fungi, viruses

46

Page 47: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

SAFETYSmoke has carcinogenic substances.

Polycyclic aromatic hydrocarbons (PAH):

Benz(o)pyrene. Thermally generated.

1-60 ppm in food.

Lower smoke generation T is better.

Use liquid smoke, or electrostatic filters.

Nitrosamines

Nitrous oxide in smoke: very low concentrations in food

47

Page 48: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

SMOKE GENERATIONWood:

Sawdust or wood chips heated to form smoke, but no flames.

Hardwood. Oak, mahogany, teak, hickory, redwood, cedar, pitch-pine.

Resinous wood: bitter taste.

48

Page 49: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

SMOKE GENERATION

Temperature:

High T: cooking, rapid drying, reaction between smoke and food.

Dry surface: less smoke absorption.

Optimum smoke generation = (550°F).

At higher T more smoke, but less active components.

49

Page 50: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

RELATIVE HUMIDITYSurface moisture is needed for smoke absorption.

60 % RH optimum

Skin-side absorbs less smoke.

Too high RH: slow drying.

50

Page 51: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

SMOKE VELOCITYFaster smoke= better penetration

Absorbed smoke near surface is replenished.

Stagnant film on surface decreased, and diffusion path shortened.

51

Page 52: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

SMOKED QUALITY

Flavor: Low T is better.

Nutritive effects: loss of vitamins

Phenols react with sulfhydryl groups

Carbonlys react with amino groups

Texture: Drying, smoke-protein interactions

Color: carbonyl-amino reactions

Phenolics

52

Page 53: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FOOD FERMENTATION

Page 54: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

UI Snack Bar

Page 55: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

What are fermented foods?

Foods or food ingredients that rely on microbial growth as part of their processing or production

Page 56: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FOOD FERMENTATION Metabolic activities occur during fermentation that:

Extend shelf life by producing acids Change flavor and texture by producing

certain compounds such as alcohol Improve the nutritive value of the

product by: Microorganisms can synthesize

vitamins Breakdown indigestible materials to

release nutrients, i.e., bound nutrients

Page 57: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FERMENTED FOODS

Foods fermented by yeast MaltBeer

Fruit (grapes) Wine

Rice Saki

Bread dough Bread

Foods fermented by mold Soybeans Soy sauce

Cheese Swiss cheese

Foods fermented by bacteria Cucumbers Dill pickles

Cabbage Sauerkraut

Cream Sour cream

Milk Yogurt

Page 58: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FOOD FERMENTATIONS – DEFINITIONS

Anaerobic breakdown of an organic substrate by an enzyme system in which the final hydrogen acceptor is an organic compound

Example:

NADH2 NAD

Pyruvic acid Lactic acid

(CH3-CO-COOH) (CH3-CHOH-COOH)

Biological processes that occur in the dark and that do not involve respiratory chains with oxygen or nitrate as electron acceptors

Page 59: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FOOD FERMENTATIONS – BIOCHEMISTRY

Sugars … Acids … Alcohols, Aldehydes

Proteins … Amino acids … Alcohols, Aldehydes

Lipids … Free fatty acids … Ketones

Page 60: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Respiration vs. fermentation

Refer to how cells generate energy from carbohydrates

RESPIRATION:• Glycolysis + TCA (Kreb’s) Cycle + Electron Transport• O2 is final electron acceptor• Glucose is completely oxidized to CO2

C6H12O6 + 6 O2 6 CO2 + 6 H2O + 38 ATP (Glucose)

Page 61: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Some organisms (facultative anaerobes), including yeast and many bacteria, can survive using either fermentation or respiration.

For facultative anaerobes, pyruvate is a fork in the metabolic road that leads to two alternative routes.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 9.18

Page 62: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.
Page 63: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Respiration vs. fermentation

FERMENTATION:• An organic compound is the final electron acceptor• Glucose is converted to one or more 1-3 carbon compounds

Examples:

C6H12O6 2 CH3-CH2OH + 2CO2 + 2 ATP

C6H12O6 2 CH3-CHOH-COOH + 2 ATP

C6H12O6 CH3-CHOH-COOH +  CH3-CH2OH + CO2 + 1 ATP

(Glucose) (ethanol)

(lactic acid)

Page 64: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

During lactic acid fermentation, pyruvate is reduced directly by NADH to form lactate (ionized form of lactic acid).

Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Page 65: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

In alcohol fermentation, pyruvate is converted to ethanol in two steps.

First, pyruvate is converted to a two-carbon compound, acetaldehyde by the removal of CO2.

Second, acetaldehyde is reduced by NADH to ethanol.

Alcohol fermentation by yeast is used in brewing and winemaking.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 9.17a

Page 66: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.
Page 67: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Carbohydrates, fats, and proteins can all be catabolized through the same pathways.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 9.19

Page 68: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Respiration vs. fermentation

Some cells can respire and ferment sugars for energy. The cell will do one or the other depending on the conditions. Example: Saccharomyces cerevisiae (baker’s, ale and wine yeast).

Some cells can only respire or only ferment sugars for energy.Example: Lactic acid bacteria produce energy by fermentation.

Page 69: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Important organisms

• lactic acid bacteria

Lactobacillus Carnobacterium

Leuconostoc Enterococcus

Pediococcus Lactococcus

Streptococcus Vagococcus

•yeasts

Saccharomyces sp. (esp. S. cerevisiae)

Zygosaccharomyces Candida

• molds

Aspergillus

Penicillium

Geotrichum

Rhizopus

Page 70: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Typical fermentation process

•substrate disappears as cell mass increases

•sugar, then other small molecules, then polymers used

•primary metabolic products (acids) accumulate during growth •pH drops if acids produced

•growth and product formation stop as substrate is depleted

•microbial succession depends on substrate and acid levels

Page 71: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Food Fermentations

In food fermentations, we exploit microorganisms’ metabolism for food production and preservation.

Where do the microorganisms come from to initiate the food fermentation?

Two ways to initiate a food fermentation…....traditional & controlled fermentations

Page 72: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

CONTROLLED VS. NATURAL FERMENTATION

Natural fermentation Create conditions to inhibit undesirable fermentation

yet allow desirable fermentation

Examples: Vegetable fermentations

Vegetables + salt

Page 73: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

CONTROLLED VS. NATURAL FERMENTATION

Controlled fermentation Deliberately add microorganisms to ensure desired fermentation

Example: fermented dairy products Lactose … Lactic acid

Starter culture

Lactics or Lactic starter or Lactic acid bacteria (LAB)

Page 74: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Traditional Fermentation

Raw material with indigenous microflora

Incubation under specific conditions

Final product

Disadvantage: Process and product are unpredictable depending on source of raw material, season, cleanliness of facility, etc.

Advantage: Some flavors unique to a region or product may only be attained this way.

= desirable m/o’s= undesirable (pathogen or spoilage) m/o’s

Page 75: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Controlled Fermentation

Raw material

Advantage: – uniformity, efficient, more control of process and product Disadvantage: Isolating the right strain(s) to inoculate is not always easy. Complexity of flavors may decrease.

Final product

Incubation under specific conditions

Add starter culture

Page 76: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Controlled Fermentations: Starter cultures

Two main starter culture types are used to inoculate the raw material:

1.Pure microbial cultures prepared specifically for a particular food fermentation. (More details on these later.)

2.“Backslop” method = Using some of the product from a previous successful fermentation to inoculate the next batch of raw material.

Page 77: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Controlled Fermentation: pure cultures

Final product

Incubation under specific conditions

Raw material

Pure culture

Add pure microbial culture

Page 78: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Controlled Fermentation: “backslop” method

Final product

Incubation under specific conditions

Add product (or byproduct) from a recent successful fermentation

Raw material

Final product from a previous fermentation (traditional or controlled)

Mainly used in home applications in the U.S. – home production of yogurt and sourdough

Page 79: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Summary

• Why we ferment foods

• Microbial energy metabolism: respiration vs.

fermentation• Traditional fermentations – indigenous microflora

• Controlled fermentations – starter culture added

Page 80: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.
Page 81: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

Food products

from milk:

cheese, yogurt, sour cream, buttermilk

lactic acid bacteria (lactobacilli, streptococci)

meats:

fermented sausages, hams, fish (Asia)

lactic acid bacteria (lactobacilli, pediococci), molds

Page 82: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

beverages:

•beer (yeasts make ethanol)

•wines (ethanol fermentation from grapes, other fruits)

•vinegar (ethanol oxidized to acetic acid)

•breads:

•sourdough (yeast + lactobacilli)

•crackers, raised breads (yeasts)

Page 83: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

single cell protein:

how cheaply and efficiently can cells be grown? waste materials as substrate (bacteria, yeast, molds) sunlight and CO2 (algae)

uses in animal feeds (frequently) or human foods

prefer protein to whole cells high nucleic acids --> kidney stones,

Page 84: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

ORGANIC ACIDS

Primary Metabolites Organic acids are. (primary products of

metabolism). During the log phase of growth the products

produced are essential to the growth of the cells. Secondary metabolites:

(Secondary products of metabolism) During the stationary phase some microbial cultures

synthesize compounds which are not produced during

the trophophase* and do not appear to have any

obvious function in cell metabolism.(idiophase*)

Page 85: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FERMENTATION

Fermentation = treat with microbes

– Desirable microbes digest food first

– Preserves food (depending on microorganism)

Makes food inedible for undesired microbes

– Alcohol, acid buildup

– Makes food digestible

Breaks down indigestible fibers

Adds nutrients

Microbially produced vitamins

85

Page 86: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FERMENTATION

In developed countries, fermentation is used to provide desired tastes and / or flavors. Preservation is a secondary benefit.

In developing countries, and the Far East, fermented aquatic products provide a significant portion of the protein need.

86

Page 87: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FERMENTATION

Since sauces and pastes prepared in these areas are salty and spicy, they provide a significant departure from a rather bland cereal diet.

Because the high salt content limits the consumption, sauces and pastes used as flavor/taste enhancers often served over rice.

Page 88: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

FERMENTATION

Fermented aquatic products are prepared by salting and then fermenting.

Salting selects desired bacteria,eliminating spoilers, prevents

putrification.

Controlling oxygen content determines characteristics. The most common putrefactive microorganisms on fish are inhibited at salt contents above 6 to 8 percent.

88

Page 89: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

EFFECTS OF FERMENTATION

Microorganisms (bacteria, yeasts, or molds), and digestive enzymes decompose the product into a soluble protein portion and a high ash portion.

The fermentation process has several benefits. The product is far more stable than the original raw product, and there is often a volume reduction.

89

Page 90: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

VARIABLES

(1) the microflora in the fish and salt,

(2) the proteolytic enzymes in the fish,

(3) initial quality of the product,

(4) presence or absence of oxygen,

(5) nutritional state of the fish,

90

Page 91: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

VARIABLES

(6) fermenting temperature,

(7) pH of the fermentation mixture,

(8) the presence of enzymes,

(9) presence/concentration of carbohydrates,

(10) the length of fermentation.

Page 92: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

QUALITY (FERMENTATION)

Calcium, magnesium, sulfate ion impurities= bitter flavor, tough texture light color.

Several techniques are available for increasing the rate of fermentation:

(1) using higher temperatures, (2) adding concentrated chemical enzymes, (3) bacterial seeding, and (4) acid additions.

92

Page 93: PRESERVATION OF FISH AND AQUATIC PRODUCTS II 2 PRESERVING  Reducing the free-water  Drying  Salting  Smoking  Chemical means  Fermentation  Pickling.

QUESTIONS?

93