Dairy

Dairy Production

• Most is milk

  • much os this goes to industry

• second is cheese

• then cream and yogurt

• then ice cream

• lowest is butter

Dairy industry quotas

• prevents the over production of milk

• ensures the everyone is not creating wasted milk

Milk Biosynthesis

• synthesized and secreted by mammary gland cells

• thousands of Kg milk in pactation periods

• smallest unit of synthesis is alveolus

  • contained in these alveoli are secretory epithelial cells

Mammary gland structure

• secretory tissue with cistern at the end

• in the large duct there is

  • blood vessels

  • capillaries

  • connective tissues

• alveolus

  • contains myoepithelial cells

  • lumen,

  • capillaries

• Secretory cell in alveoli

  • nulceus,

  • lipid droplets

  • free ribosomes

  • mitochondria etc

large duct of mammary gland

• has lots of blood flow

• this is why milk has pH similar to blood through the interaction of the two

• lactose is synthesized at goli

  • into vesicles emptying into luminal side

• connects to where the milk exits

Alveolus

• duct connection

• lumen is where the protein, sugar and fat go once synthesized

Secretory cells

• golgi adds sugars and modifies products

• move into lumen

  • then it can fuse with membrane and empty into the lumin

• allows fat, sugars etc to enter the milk flow

Holstein cows

• bread to produce large volumes of milk during lactation

• calf stays with the mother in order to have good growth and to stimulate milk production

• fed non-pesticide foods to allow for better products

Swiss dairy cows and jersey cows

• well kept

• jersey cows are aggressive cows

  • have a higher fat content and are used for clotted cream

Milking technology

• modern farm technology attaches cups to milk the cows

• cleaned and sanitized to ensure good quality products being made

cooling milk

• milk must be reducte din temperature from 37 degrees to 4 degrees quickly

  • taken out of the danger zone

• uses a plate heat exchanger

  • cold water on one side and the milk will flow over the plates to cool quickly

  • this is an energy efficient mechanism of cooling milk

Milk testing

• must be tested for foodborne pathogens

  • especially Escherichia coli

• is also tested for levels of fat, sugars etc

Milk composition

• large proportion water 86-88%

• fat 3.4-5.1%

  • amount depends on the cows

    • eg jersey cows have higher levels of fats

• protein 3.6%

• lactose 5.0%

  • has lower lactose than human milks

• ash - minerals 0.7%

• salts

  • calcium, Mg, PO4--, NaCl, citrates (citric acid salts)

Milk freezing

• freezes at -0.57 degrees celcius

  • allows for a way to check how much water is in the product

Dairy scams

• the producers make more money if they have a higher amount of product

  • they are also priced based on fat content

• if farmers have a higher fat content milk, they could water it down to make a lower fat product that also has a hgiher volume

• they can get caught cause the product will freeze at a higher temperatuer

Milk proteins

• Caseins - 80%

• Whey - 20%

Casein proteins

• these are not very heat sensitive

  • will not denature below 100 degrees celsius

• alpha - s caseins - 40% proteins

• beta caseins - 25% of proteins

• K-casein - 9%

  • K is glycosolated with one or more glucose on its strutcture

    • beta and k are both phosphorylated at the rough ER

Whey proteins

• easily denatured at >70 degrtees

• water soluble → heated → now insoluble

  • will remain on top of the milk anf form the film that is seen with heated milk products

types of whey proteins

• beta-lactoglobulins

  • this is what is responsible for allergic reatctions to milk (not lactose intolerence)

• alpha-lactablumin

• Blood proteins

  • serum albumin

  • immunoglobulins

Blood proteins in whey

• important part of immune system antibodies

• this is why it is important for calf to spend time with the mother

  • allows for passive immunity

• collustrum in milk - yellow milk

  • high in antibodies to allow for apsstive immunity to beformed

Milk Lipid profile

• ?????

Milk fat and processing

• remove/skim off the fat from the top

  • butter, cream whipped cream

    • want more fat in these products

• residual fat can undergo honogenization

  • this involes forcing the fat through small holes to break them into smaller dropplets

    • this makes it harder for the fat to seperate and float to the top of the water preventing milk separation in higher fat milks

    • fat floats cause it si less dense

Minerals and salts of milk

• Ca++

  • soluble Ca - Whey

  • Semi-soluble Ca with casein proteins

    • after digestion the formation of phosphopeptides allows it to remain soluble in the intestine

• Mg++

• Citrates (citric acid salts)

• CaPO4

• NaCl

Heating of milk

• cooked flavour occurs because of the release of H2S

• sulphur amino acids contain SH and SS bonds exchange and form the H2S

  • often in methionine and cysteine amino acids

Sulfur amino acids

• methionine and cysteine

Acid and milk proteins

• involved in the formation of gel/ coagulation of milk proteins

  • Yogurt - lactic acid

  • H20 gets trapped int eh gel

• Milk pH of 6.6

  • casiens with a charge

  • have isoelectric point of 4.6

Casein isoelectric point (PI)

• 4.6

• this means they are least soluble at 4.6 pH

  • this is related to lactic. acid production

• usually htey ahve a - charge cause of the phosphate group

  • lactic acid production results in bonds with the - charge

    • hydrogen bonds neutrilize the charge

Enzymes (rennin) - rennet in lab

• chymosin - liquid is the naturally occuring product

  • this is replaced by rennet which is biologically created

• Casein proteins are found in spheres and k-casein exists within these with a phydrophobic and hyrdophillic end

• the balls are called the casien micelle

  • rennet will cleave the hydrophili end off resulting in the individual casein molecules clustering together

  • this creates coaggulation and trapping of moisture within the brpduct

Milk protein fouling

• occurs when proteins precipitate onto the surface of the product

  • in a pot of sauce there is a sticking of whey proteins

• denatured whey proteins

  • 70 degrees or more

• protein + Ca + lactose

  • all 3 precipitate in overheating of the product

Milk pasteurization

• occurs 63-72 degrees and must eb careful to not denature the whey proteins

Skin formation on milk surface

• denaturation and dehydration of the product

  • prevented with stirring

    • foaming milk will also help to prevent

Milk curdling

• similar to custards

• slow denaturation of whey and casein proteins → forming a gel

  • heating of the product to 100 degrees

    • temperature of casein denaturation

    • especually when held at this heat for long periods of time

  • creates a semisolid gel