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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
Terms To Know Buttermilk Churning Coalesce Curd HTST Lipolysis LTLT Rennet Ripening Ropey Solids-not-fat Standard plate count
(SPC) standardized
Ropey Solids-not-fat Standard plate count
(SPC) standardized Thermization UHT Ultrapasteurization Vaccum evaporation Whey
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
Butter Churns From the Past
Today’s Butter Churn
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
Yogurt Semisolid fermented milk product Originated in Bulgaria Milk from a variety of animals is used in
yogurt production but most of the industrialized nations use cow’s milk
Starter culture used in most yogurt production is a blend of Streptococcus salivarius thermophilus (ST) and Lactobacillus delbruekii bulgaricus (LB)
Making Yogurt Milk is clarified and separated into cream
and skim milk Standardized to achieve the desired fat
content Various ingredients are blended together
in a mix tank equipped with a power funnel and an agitation system
Mixture is then pasteurized Once the homgenized mix has cooled to
an optimum growth temperature, the yogurt starter culture is added
Fermented Milk Beverages Cultured Buttermilk
Once a by-product of butter production, now produced from whole or skim milk
Acidophilus Milk Traditional milk fermented with LA which is
thought to have therapeutic benefits in the gastrointestinal tract
Sour Cream Others
Ice Cream (start) Greater than 10% milk fat by legal definition As high as 16% fat in some premium ice cream 9-12% milk solids-not-fat Also contains 12-16% sweeteners-usually a
combination of sucrose and glucose-based corn syrup sweeteners
0.2-0.5% stabilizers and emulsifiers 55-64% water from the milk or other ingredients When frozen about half the volume of ice cream
is air All ice cream is made from a basic white mix
Basic Steps In Manufacturing Ice Cream Blending of the mix ingredients Pasteurization Homogenization Aging the mix Freezing Packaging Hardening
Quality Products Established by USDA Grades are used to describe different grades
of quality in butter, cheese (Cheddar, Colby, Monterey, Swiss)
FDA established the Grade A designation for fluid milk products, yogurt and cottage cheese
Grade standards are used to Identify levels of quality Provide a basis for establishing prices at wholesale Supply Conumers with a choice of quality levels
Milk Substitutes Margarine Frozen desserts Coffee whiteners Whipped toppings Soy milk
All are made by combining nondairy fats with certain classes of milk components
Reduced Fat Products Brought on to the market in the effort to
reduce calories, saturated fat, cholesterol When fat is replaced the replacement
must perform the same functions as the fat. It must give the product the same texture or
“mouth feel” Why? What would consumer repsonse be if it didn’t?
Summary Milk provides high quality protein, energy, vitamins, minerals Dairy industry provides a variety of milk products USDA and FDA maintain quality standards Milk is pasteurized to protect consumers against pathogens Milk is homogenized to keep milk fat in suspension Butterfat is separated from the milk to be added back in in the
desired amounts Concentrated and dried products increase shelf life and
convenience and decrease transportation costs USDA established grade standards for butter, cheese and instant
nonfat dry milk FDA established grade designations for fluid milk, yogurt, cottage
cheese Only officially graded products carry a grade shield In an effort to meet consumer demands the food industry has
developed milk and milk substitutes and reduced fat products
Lab Making Butter
STUDENT ACTIVITY Develop a presentation comparing BUTTER
to MARGARINE Compare their make-up (ie-butter is made
from milk fat and margarine is made from vegetable oil)
Compare their healthfullness Find pictures Make a poster