PowerPoint Presentation

By: Solomon A.Dairy product processing and marketing

Week-1Objectives: Dictation on:Principles of dairy production, processing and marketingImportance of dairy product processing and marketing

1. Principles of dairy production, processing and marketingDairy producers ensure the safety and quality of their products will satisfy the highest expectations of the food industry and consumers.

On-farm practices should ensure that milk is produced by healthy cattle under sustainable economic, social and environmental conditions.

It is important to note that the focus of these Principles and Practices is on the desired outcomes, rather than on specific, prescriptive actions/processes.

It is important to note that good management of a farming system constitutes the grassroots of the systems economic, environmental and social sustainability.

Sustainable Farming Site selection and managementSustainability management systemAnimal breedAnimal healthMilking hygiene, milk storage and milk safetyAnimal feeding and waterAnimal welfare

Economic SustainabilitySafety, quality and transparencyFinancial and market stabilitySocial SustainabilityEnvironmental Sustainability

Objectives: Lecture on: Physics and chemistry of dairy productsComposition of milk

Week-2

What is milk?Milk is secreted by the mammary glands of mammals to feed their young. It is also described as a colloidal suspension, containing emulsified globules of fat, a heterogeneous family of major and minor proteins, the carbohydrate lactose, minerals, vitamins and enzymes.

Cow milk is a white fluid of low viscosity and slightly sweet taste, most commonly used as human food. Species Total solids Fat Protein Lactose AshHuman 12.4 3.8 1.0 7.0 0.2Cow 12.7 3.7 3.4 4.8 0.7Goat 12.3 4.5 2.9 4.1 0.8Sheep 19.3 7.4 5.5 4.8 1.0Domestic rabbit 32.8 18.3 13.9 2.1 1.8Camel 12.9 4.2 3.7 4.1 0.9

Milk composition of some species of mammal.

ProteinsIt is found partly in solution and partly in colloidal suspensionCows milk protein is commonly divided into two classes on the basis of the solubility at pH 4.6: the insoluble caseins and the soluble whey (or serum) proteins. Whey proteinsRepresent 20% of total milk protein in cows milk. In their native form are soluble at pH 4.6 or in saturated NaCl, It remain soluble after rennet-induced coagulation of casein micelles and cannot be sedimented by ultracentrifugation. It consists a number of proteins, primarily -lactoglobulin (-lg), -lactalbumin (-la), blood serum albumin, immunoglobulins and proteose peptones.

-lactoglobulin-lg is the first most abundant whey protein. It is synthesized in the epithelial cells of the mammary gland. Monomeric cows -lg consists of 162 residues per monomer. In cows milk at natural milk pH, it is found in the form of dimers, formed through hydrophobic interaction.

-Lactalbumin -La is the second most abundant whey protein in cows milk. It consists the polypeptide chain of 123 amino acid residues. Synthesized in the rough endoplasmic reticulum; and then transported to the Golgi apparatus, where it has an important function in the synthesis of lactose. It contains eight cysteine residues, which form four intra-molecular disulphide bonds, and contain a tightly bound calcium ion.

Serum albumin (SA) It is the most abundant protein in the circulatory system of the cow, It consisting of 50% of the protein in bovine blood serum, but present in small quantities in milk (0.10.4 g/L). It consists of 582 amino acids; contains 17 disulphide bonds and one free sulphydryl group. It has little influence on the properties of cows milk.

Immnoglobulins (Ig) It is present in the colostrum and, milk of all lactating species It providing immunological protection to the offspringIts level is very high in the colostrum, but will decline rapidly. The Ig classes of cows milk are IgG, IgM and IgA. IgG occurs predominantly in two subclasses, IgG1 and IgG2. IgM plays an important role in the creaming of cows milk.

Proteose peptonesThey are often classified as the pH 4.6-soluble proteins They are not denatured by heat treatment, but are insoluble in 12 g /100 mL trichloroacetic acid. Its fractions of milk appears to consist of two groups of proteins/peptides; osteopontin, and proteose peptone 3 (PP3)They are derived from the action of proteolytic enzymes, primarily plasmin, on caseins.

CaseinsThe caseins represent 80% of total protein in cows milk. The caseins are a class of phosphoproteins whose properties differ considerably from most other proteins; They are hydrophobic, have a relatively high charge and contain many proline and only few cysteine residues. Cows milk contains four types of caseins, denoted s1-casein, s2-casein, -casein and -casein, which occur at a ratio of 4:1:4:1.6, respectively.

s1-CaseinIt has the highest charge; consists of 199 amino acids and contains eight phosphoserine residues per molecule. Exhibits progressive self-association to dimers, tetramers, hexamers, etc. s1-Casein is easily precipitated by addition of calcium.

s2-CaseinIt is the least abundant of the caseins It is the least hydrophobic and most highly and variably phosphorylated of the caseins. Consist 207 amino acid residues and behaves very similarly to s1-casein.

-Casein It is the most hydrophobic of the caseins and contains a large number of proline residues, has a hydrophilic C-terminal end and a very hydrophobic N-terminal end. Consists of 209 amino acid residues contains five phosphoseryl groups. -Casein is readily cleaved by the indigenous milk proteinase, and plasmin enzyemsWhich leading to the formation of -caseins and proteose peptones. -Casein is precipitated in the presence of calcium and, at a temperature >50C, -casein molecules undergo self-association, leading to the formation of micelles.

-Casein It is differs from the other caseins, because it is glycosylated. Approximately 2/3 of the molecules are glycosylated; carbohydrate groups include galactosamine, galactose and N-acetylneuraminic acid residues.It is amphiphatic, with a very hydrophobic N-terminal end and a rather hydrophilic C-terminal end, important in stabilizing the casein micelles. It consists of 169 amino acid residues. Unlike the other caseins, it is not sensitive to calcium, but it does, like -casein, tend to form micelles in solution.

Casein micellesCasein micelles are the amphiphilic nature of caseins and their phosphorylation facilitate interaction with each other and with calcium phosphate to form highly hydrated spherical complexes. It consists of an aggregate of spherical sub-micelles. Calcium phosphate and -s and -casein are linked by the involvement of the phosphoserine residues in the structure of the calcium phosphate. -Casein is localized on, or very close to, the surface of the casein micelle.

LactoseIt is a disaccharide which is present in milk of most mammalian species. Cows milk contains small amounts of other carbohydrates also occur; 10 mg/L monosaccharides (glucose and galactose) and 100 mg/L oligosaccharides. It is responsible for 50% of the osmotic pressure of cows milk. The concentration of lactose decreases progressively and significantly with lactation stageincreasing somatic cell count of the milk; In both cases, this is due to the influx of NaCl from the blood and the resultant need for a reduction in lactose concentration to maintain the osmotic equilibrium.

Lactose is synthesized from glucose in the Golgi apparatus of the mammary secretory cells. The whey protein -lactalbumin plays an important role in the synthesis of lactoseBecause -lactalbumin has the ability to, if necessary, terminate the synthesis of lactose and regulate and control osmotic pressure.

LipidsCows milk compose of 98% triglycerides and 1% phospholipids, plus small amounts of diglycerides, monoglycerides, cholesterol, cholesteryl esters and traces of fat soluble vitamins and other lipids.

Over 400 different fatty acids have been detected in cows milk fat, although most occur only in trace amounts.

Milk fat globulesAlmost all the lipids in milk are found in milk fat globules Milk can be considered as an oil-in-water emulsion. Cows milk typically contains >1010 milk fat globules per milliliter.

Globules are naturally emulsified by a surface layer, the milk fat globule membrane (MFGM). The MFGM resembles the mammary cell membrane, from which it is largely derived, quite closely, and consists protein including enzymes such as alkaline phosphatase and xanthine oxidase, phospholipids, cerebrosides, Cholesterol, other substances (neutral glycerides, water, caretenoids, vitamin A, iron and copper) are also present at lower levels.

Milk saltsThe primary salts in milk are phosphates, citrates, chlorides, sulphates, carbonates and bicarbonates of sodium, potassium, calcium and magnesium. Since milk contains organic and inorganic salts, the level of salts is not equivalent to the level of mineral substances, and the level of salts is by no means equivalent to the ash content. Salts exist partially in soluble form and partially in a colloidal form, i.e. associated with the casein micelles. The colloidal salts are commonly referred to as micellar calcium phosphate (MCP) or colloidal calcium phosphate (CCP), although some magnesium and citrate are also present. MCP plays an important role in the structure and stability of the casein micelle.

VitaminsThe concentration of fat-soluble vitamins A, D, E, and K, and water-soluble vitamins B and C and other minor constituents are found. Bovine milk contains Thiamine (B1), Riboflavin (B2), Niacin, Pyridoxine (B6), Pantothenic acid, Biotin, Folic acid, Vitamin B12, Vitamin C, Vitamin A, Vitamin D, Vitamin E and Vitamin K.

Milk enzymesMilk contains a large number of enzymes approximately 60. They occur in various states: Unassociated forms in solution, Associated or an integral part of membrane fractions,Associated with casein micelles, and Part of the microsomal particles.They can affect by processing and storage conditions of milk. They origin from udder (synthesized enzymes) or from bacterial enzymes (bacterial source). Several of the enzymes in milk are tested for quality assurance of raw milk and processed milk products. Enzymes associated with membrane fractions will occur in both cream and skim milk.

Enzymes known or potential for technological significance are: Plasmin, Lipoprotein lipase, Alkaline phosphatase, Lactoperoxidaes, Sulhydryl oxidase, N-acetyl--D-glucosaminidase, Catalase, Xanthine oxidase, Superoxide dismutase, -glutaryltransferase, and Lactose synthase.

Objectives: Lecture and discussion on: Biosynthesis of milkWeek-3

Biosynthesis of milk constituentsMammary glandBiosynthesis of milk proteins

The substrate, amino acids from blood, is transported through the basolateral membrane to mammary secretory cell. The transporting systems may be sodium dependent or independent. Different groups of amino acids require different transporting system. The biosynthesis is initiated by gene expression

Following essential steps are involved in protein biosynthesis:TranscriptionActivationTranslation

Milk EnzymesMany enzymes in milk are original enzymes coming from the cows udder.

Biosynthesis of milk lipids

Biosynthesis of milk sugar, lactose

Secretion of milk constituents into lumen

Rate of milk secretionIt is related to time since the previous milking of the cow. After 10 hours from previous milking, the average secreting rate slows down and after 35 hours it stops completely.

Structural and Physical properties of milkMilk is a fluid with characteristics of three physical phases: Emulsion, Colloidal dispersion, and Solution. Milk lipids present as an oil-in-water type emulsion can be broken by low-speed centrifugation and the milk separates into lipid and aqueous phases, each with a characteristic composition. Colloidal phase contains casein micelles, calcium phosphates, and globular proteins. Whey proteins are in colloidal solution and the casein is in colloidal suspension.

Lactose, vitamins, acids, enzymes, and some inorganic salts are present as true solutions. The physical equilibrium of milk destabilize by factors such as addition of polyvalent insoluble salts; concentration of serum solids; changes in pH; heat treatment; and addition of precipitant such as alcohol. These factors can change the structure of milk and its physical equilibrium.

The physical properties of milk are of great importance to the dairy technologist, They will affect most of the unit operations during processing. These include fluid flow, mixing and churning, emulsification and homogenization, and alsoheat transfer processes such as pasteurization, sterilization, evaporation, dehydration, chilling, and freezing.

Objectives: Lecture and discussion on: Influences on milk quality Week-4

Influences on milk qualityInterval between milkingThe fat content of milk varies SNF content does not vary

Stage of lactationFat, lactose and protein contents of milk vary SNF content is highest the first 2-3 weeks, then decreases slightly. Fat content is high immediately after calving but fall for 10 to 12 weeks, and then tends to rise again until the end. High protein content of early lactation milk is due mainly to the high globulin content.

Age and healthAs cows grow olderfat content decreases by about 0.02% SNF content fall about 0.04%. But both fat and SNF contents can be reduced by disease.

Feeding regimeUnderfeeding reduces both the fat and the SNF content of milk. SNF content may fall if fed a low-energy diet, but is not greatly influenced by protein deficiency, unless the deficiency is acute.Fat content and fat composition are influenced more by roughage intake.

Completeness of milkingThe first milk drawn from the udder contains about 1.4% fat while the last milk contains about 8.7% fat.

Objectives: Lecture and discussion on: Dairy products analysis Purpose of Analysis of dairy productsSampling techniquesTypes of analysis Tests for milk compositionTests for milk qualityWeek-5

Purpose of Analysis of dairy products

What are the purpose of analyzing the dairy products?

Sampling techniquesAccurate and representative sample must be obtained.Milk must be mixed thoroughly before sampling and analysis to ensure a representative sample. If the volume of milk is small, e.g. from an individual cow, the milk may be poured from one bucket to another and a sample of milk taken immediately. If large volumes of milk are handled, the milk or cream must be mixed by stirring thoroughly; and small samples taken from three or more places of the container. For best results, milk or cream must be sampled at temperatures between 15 and 32C. Sour milk or cream, in which casein has coagulated, must be sampled frequently.

If the milk or cream has been standing for a long time and a deposit has formed on the surface and sides of the container, it should be warmed while agitating before a sample is removed. For certain analyses, milk samples can be preserved and stored. Samples of milk or cream for butterfat analysis can be preserved using formalin or potassium dichromate. Plungers and dippers are used in sampling milk from milk cans/ bulk tanks.

Sampling for bacteriological testingDippers should be sterilized in an autoclave or pressure cooker for 15 minutes at 120C before use.On-the-spot sterilization with 70% alcohol swab and flaming, or scalding in hot steam may also be used.

Preservation of milk samplesIf a milk sample cannot be analyzed immediately after sampling: It must be cooled quickly to near freezing point until transported to the laboratory. If samples are taken from field they can be preserved in ice boxes with ice packs. Milk samples cooled in a refrigerator or ice-box must first be warmed in 40C water bath then cooled to 20C and mixed well before analysis.

Milk samples for butterfat testing may be preserved with potassium dichromate one tablet or 0.5 ml of a 4% solution in a 0.25 liter sample bottle is adequate. Other chemical preservatives include 0.08% sodium azide and 0.02% Bronopol.

Labeling and record keepingSamples must be clearly labeled with:the name or code number of farmer, date of sampling and the place where the sample was collected. This information should also be included in standard data sheets. Records must be kept neat and stored in a dry place.

Types of analysis Tests for milk compositionFat determinationTotal solids (TS) in milkDetermination of protein content of milk by formaldehyde (formal) titration

Tests for milk qualityPhysiochemical quality Milk pHMeasuring pH using indicatorElectrometric measurement of pHTitratable acidity test

Alcohol testClot-on-boiling testSpecific gravity of milkFormaldehyde in milk

Microbiological quality Methylene blue reduction testResazurin 10-minute test

Sensory evaluation of dairy products

Objectives: Lecture and discussion on: Unit operations in dairy products processing Receiving and storage of milkStraining, filtration and clarificationStandardizationPasteurizationSterilizationHomogenizationCream separationMembrane processingWeek-6

Receiving and storage of milkMilk collection When milk is brought from the farm to the dairy for processing the following information on the milk is required:Quality: acidity, pH, alcohol and clot-on-boilingQuantityComposition: total solids (TS), specific gravityPresence of contaminants - neutralizers, preservatives etcAdulteration: fat, titratable acidity and specific gravity tests

Milk storage

Straining, filtration and clarification The object is to improve aesthetic quality of milk by removing visible foreign matter which is unsightly and may therefore, cause consumer complaints.Straining is separation milk according to breed, health states of animal and so Filtration is removes suspended foreign particles by the straining process, Clarification is removes the same by centrifugal sedimentation

StandardizationThe adjustment of fat and SNF of milk to the desired level, to meet the legal standardsCorrect calculations by Pearsons method regarding ingredients to be used for standardization

PasteurizationPasteurization is the most common process used to destroy bacteria in milk. In pasteurization, the milk is heated to a temperature sufficient to kill pathogenic bacteria, but well below its boiling point. Also kills many non-pathogenic organisms and thereby extends the storage stability of the milk.

Numerous time-temperature combinations are recommended

High Temperature Short Time (HTST) treatmentIs 72C for 15 seconds followed by rapid (less than 2 minutes) cooling to below 10C. Batch pasteurization Fixed quantities of milk are heated to 63C and held at this temperature for 30 minutes.The milk is then cooled to 5C using iced or cold water before packing.

Effects of pasteurization on milkFat Reduces the cream layer. Inhibits clustering of the fat globules and consequently reduces the extent of creaming. However, it does not reduce the fat content of milk.Nutritive valueIt has little effect and the major nutrients are not altered. It has insignificant loss of vitamin C and vitamin B group.The process kills many fermentative organisms as well as pathogens but putrefactive micro-organisms survive.

SterilizationEnsures almost complete destruction of the microbial population. Time/temperature treatments of above 100C for 15 to 40 minutes. The product has a much longer shelf-life than pasteurized milk.

Ultra high temperature treatment (UHT). Milk is heated under pressure to about 140C for 4 seconds. It retains more of the properties of fresh milk than conventionally sterilized milk.

Homogenization

Cream separation

Membrane processingSeparation of dairy fluids using semi-permeable membranes has been used to clarify, concentrate and fractionate a variety of dairy products.

Objectives: Lecture and discussion on: Dairy products manufacturing Beverage milkConcentrated and dried dairy productsIce creamButterCheesesYoghurt and other cultured milk by productsWeek-7

Beverage milk

Concentrated and dried dairy productsThe unit processes in the manufacture of dry milk products include standardization, preheating, concentration, homogenization, and drying. The approximate compositions of the milk powder products are as follows: Skim milk powder: 36% protein,