MILK

Objectives Define the term “milk” Describe quality control during the production of milk and

milk products Explain pasteurization and homogenization Identify three methods of pasteurization Describe the “solids” composition of milk Discuss the separation of butterfat and its use List four beverage milk products Describe butter Name 5 concentrated or dried dairy products List the steps in the cheese making process Identify 3 bacteria used to produce dairy products Name 5 fermented dairy products List the steps in making and ice cream and make ice cream Describe the USDA quality grade shields

Introduction Milk: the first food for young mammals Provides high quality protein, vitamins and

minerals and is a source of energy Worldwide many mammilian species are used to

produce milk and milk products Goats, sheep, horses, yaks

However, our focus will be on milk from dairy cows

Fluid Milk

Fluid Milk Collodial dispersion of the protein caesin and

the whey proteins. It is an emulsion with fat globules suspeneded in the water phase

Composed mainly of water 87-89%

Milk solids make up the other 12-13% Solids include the carbs, lactose, fat,

protein and minerals Solids-not-fat

Excludes the fat and includes the caesin, whey, lactose, proteins, minerals

Production Practices Fewer cows are producing more milk Daries are becoming larger In major production areas daries are 1,000 cows

or more Milk fresh from the cow is virtually sterile Post handling must maintain the milks nutritional

value and prevent deterioration caused by physical and biological changes

Equipement must be maintained to government and industry standards

Production Practices Cows are milked twice a day

Some farms milk 3-4 times/day Milk is immediately cooled from the body

temperture of the cow to below 41 degrees F

It is then stored at the farm under refrigeration until it is picked up by tanker trucks at least every other day A sample of the milk is collected at this time

for later lab analysis

Quality Control On the farm

Inspectors monitor herd health, farm water supply, sanitation, milk temperture, holding times, bacteria counts

Violations of health standards result in heavy penalties up to and including suspension from business

Inspections occur both at the farm and processing plants on a regular on-going basis

Inspectors have full authority to suspend plant operations in order to conduct detailed examinations of all equipment, facilities and products

The dairy industry works hard to ensure that they comply with or exceed all regulations

Quality Control Finished dairy products

Tested regularly by state inspectors to ensure compliance with

Standards of Identity Refers to criteria such as mouisture,

butterfat, protein content Purity

Refers to pathogens and residues criteria

The Food and Drug Administration (FDA) sets the standards of identity for beverage milk products

Processing When milk arrives at the plant it is checked

to make sure that it meets the standards for temperture, total acidity, flavor, odor, tanker cleanliness and absence of antibiotics

Butterfat and solids-not-fat content is analyzed These amounts will vary with the feed, breed of

cow and time of year These are also used along with the volume to

determine what the producer will be paid Once the milk passes these receiving test it is

pumped into large refrigerated silos

Pasteurizing Heating the raw milk to kill all pathogenic

microoranisms that may be present Not sterilization After pasteurization some harmless

bacteria may still be present these are the bacteria that cause milk

to go sour Refrigeration is the best way to slow the

growth of these organisims

Pasteurizing Low Temperture Longer Time (LTLT)

Heats milk to at least 145 degrees F for at least 30 minutes Can cause a “cooked” flavor Not used by some milk plants for fluid milk products

High Temperture/Short Time (HTST) Heats milk to at least 161 degrees F for at least 15 seconds Milk is immediately cooled to below 40 degrees F and

packaged in plastic jugs or plastic coated cartons Ultrapasteurization

Heating milk to 280 degrees F or higher for 2 seconds followed by rapid cooling to 45 degrees or less

Ultrahigh Temperture Processing Sterilizes the milk Heats it to 280-302 degrees for 2 to 6 seconds Milk is aseptically packaged and does not require

refrigeration until it is opened

Butterfat Several different types of product

Whole milk, 2%, 1%, nonfat, Half & Half Seperated using separator that separates

the cream and skim portions of the milk For example: During the separation of

whole milk two streams are produced: the fat-depleted stream, which the above mentioned beverage milks are made of; skim milk for evaporation and/or drying and the fat-rich stream, the cream

Butterfat: Cream Comes from the separator with a fat

content of 35-45% Used for further processing in the dairy

industry—ice cream, butter

Homogenization Prevents the cream from rising to the top A “homogenizer” forces milk under high

pressuure through a valve that breaks up butterfat globules to such a small size that they will not coalesce (stick together)

Does not affect the nutrion or quality

Beverage Milk Most raw milk fat content is 4% or higher Most beverage milk is 3.4% Lower fat contents- 2%, 1%, Skim

These products are produced by partial or complete skimming and then adding cream back to achieve the final desired fat content

Nutritional Qualities Vitamins may be added

A & D most often due to their loss A during fat separation and heating D because it is not present in milk

Supplemeted in the form of a water-soluble emulsion

Many states have milk standards that require the addition of milk solids These represent the natural mineral, protein,

and sugar portion of nonfat dry milk

Quality Control Numerous test on raw and paterurized product Microbial organisims are tested for using the

standard plate count (SPC) and ropey milk test Equipment used to analyze butterfat and solids-

not-fat is calibrated on a regular basis to ensure consistency

All products have a sell-by date Samples of the products packaged each day are

saved to confirm they maintain their freshness 7 days after the sell-by date

Packaging Once milk is separated, standardized, homogenized and

pasteurized it is held below 40 degrees F Then it is packaged into gallon, ½ gallon, quart, pint and

half pint containers Packaging machines are maintained under strict standards All equipment is washed daily Automatic clean-in-place systems guarantee consistent

sanitation with minimum manual handling to reduce the risk of contamination

Once packaged the products are conveyored to cold storage where they are stored for a short time before being shipped to supermarkets where they are kept in cold storage or refrigerated display cases

Milk Products and By-Products

Milk Products and By-Products Include

Butter Concentrated and dried milk Cheese Whey products Yogurt Fermented products Ice Cream

Butter Made by churning pasteurized cream Churning breaks up the fat globule

membrane This breaks the emulsion, fat coalesces and the

water (buttermilk) escapes Federal law requires that it contain at least

80% milkfat, nutritionally butter is a fat. Salt and coloring may be added Today commercial butter making is a

product of knowledge and experience gained over the years

Butter Make-Up Normal Salted Butter

Fat 80-82% Water 15.6-17.6% Salt 1.2% Proteins, Calcium, Phosphorous 1.2% Also contains fat soluble vitamins A, D, E

Butter Should have uniform color Be dense Taste clean Water should be dispersed in fine droplets

so that the butter looks dry Consistency should be smooth so that it is

easy to spread and melts readily on the tongue

Making Butter From storage tanks the cream goes to pasteurization

This destroys enzymes and microorganisms that would impair the keeping quality of the butter

Next, ripening Here the cream is subject to a program of heat treatments

designed to give the fat the necessary crystaline structure so it solidifies on cooling

Takes 12-15 hours Churning

Cream is violently agitated This breaks down the fat globules, causing the fat to coagulate into

butter grains, leaving the liquid part (buttermilk) Butter is salted and worked to ensure even distribution Packaged Sent to cold storage

Concentrated and Dried Dairy Products Concentrated products have partial water

removal Dried products have water removed to

less than 4% Benefits of both products are

Increased shelf life Convenience Product flexibility Decreased transportation costs Storage

Concentrated and Dried Dairy Products Concentrated Products

Evaporated skim or whole milk

Sweetened condensed milk

Condensed buttermilk

Condensed whey

Dried Products Milk Powder Whey Powder Whey Protein

concentrates

Cheese Traditionally cheese was made as a way of

preserving the nutrients of milk Cheese- the fresh or ripened product

obtained after coagulation and whey seperation of milk, cream, or partly skimmed milk, buttermilk or a mixture of these

THOUSANDS of varieties

Cheese Making Steps Treat milk Additives Inoculation and milk ripening Coagulation Enzyme Acid Heat-acid Curd Treatment Cheese ripening