Animal, Plant & Soil Science Lesson C7-5 Processing Dairy Products.

Animal, Plant & Soil Science

Lesson C7-5Processing Dairy Products

Interest Approach Display a number of dairy food products.

As a class, discuss what makes these products similar and different. Ask the students how they can tell if the products are “true” dairy products. What are the steps required to transform milk into solid products? Have students taste test milk products and discuss the different flavors. Discuss the nutritive value and wholesomeness of milk. Take time to discuss lactose intolerance and the need for substitute products.

Objectives Describe the steps in processing milk;

identify the types of milk; and explain how milk is graded and classified.

Describe samples of milk for flavor and odor, and critique milker head units for defects.

Describe the steps of the cheese-making process, and identify the four groups of cheese.

Objectives Identify samples of cheese. Describe the steps of the yogurt-,

sour-cream-, and cottage-cheese-making processes.

Describe the steps of the butter-making process and the butter types.

Objectives Describe the marketing options for

dairy products. Distinguish between real and artificial

dairy foods.

Terms cattle byproducts cheddaring curd curdling homogenization

pasteurization solids-not-fat (SNF) standard plate count

(SPC) standardized whey

What are the steps involved in processing milk? What are the types of milk? How do you grade and classify milk?

Milk processing involves many steps. All farm equipment must be kept and

maintained to government and industry standards to ensure safe, healthy, and quality products.

After dairy cows are milked, the liquid is cooled from the cow’s body temperature to below 40°F (4°C).

It is refrigerated until the milk tanker driver arrives to record the amount of milk, make special notes of the milk temperature and odors, and transport the product.


A. At the milk processing plant, samples are checked for proper temperature, total acidity, flavor, odor, cleanliness, and the absence of antibiotics. The butterfat and solids-not-fat

are also analyzed. Solids-not-fat (SNF) contain the

protein, lactose, and minerals and are the total solid minus the milk fat.

The amounts of butterfat and SNF can vary because of cow breed, feed supply, and the time of year.

Many producers depend on these counts for contract payments.


B. Within 72 hours, the milk must be processed. The milk is pasteurized at the processing plant. 1. Pasteurization is the process of heating the

milk to destroy all pathogenic bacteria. Milk can be pasteurized by heating it to 161°F (72°C) for 15 seconds.

Then the milk is immediately cooled below 40°F (4°C). 2. Ultrapasteurization is used to extend the

shelf life of refrigerated products and to enable products to be kept at room temperature.


C. Milk is then standardized. Milk is processed through

centrifugal separators to create a skim portion and a cream portion.

Most milk in the United States is standardized. The cream portion is added back to the skim

portion based on the desired fat content for the product.

Water is never added to lower the butterfat. The extra cream from this step is used to make

ice cream or butter.


1. Common products/types of fluid milk a. Whole milk b. Low-fat milk c. Skim milk d. Flavored milk

2. Major types of milk a. Fluid milk b. Manufactured milk products (evaporated

milk and sweetened condensed milk) c. Powdered milk d. Specialty milk (multi-vitamin, lactose-

treated, or low-sodium)


D. Homogenization is the process used to prevent the cream from rising to the top of a finished milk package. Homogenization reduces the

milk fat globule size, allowing for even distribution in milk.

This process does not affect the nutrition or quality of the product; it keeps the final product from forming a cream topping.


E. Vitamin quantities are often reduced as a result of the heating process and the removal of butterfat, so milk is commonly fortified with vitamins A and D.

1. Vitamin A is a fat-soluble vitamin. a. Whole milk is known as a good source of

vitamin A because of the higher fat content. b. There are lower quantities of vitamin A in 2 percent, 1

percent, and skim milk. 2. Vitamin D is also a fat-soluble vitamin that

occurs naturally in milk at low levels. a. The process of vitamin D fortification started in the

1930s to reduce the occurrence of rickets in children. b. Today, vitamin D is necessary for human health.


F. Quality control is conducted through all of the steps in milk processing. Numerous tests and samples are gathered to analyze the

presence of microbiological organisms. 1. A standard plate count (SPC) is performed

to determine the total number of bacteria for a specific amount of milk. This test is used in the grading procedure.

2. Milk can be Grade A or Grade B. (Grades are not the same as classes of milk.) a. Grade A milk meets the sanitary standards for fluid

milk products and can be used for any dairy product. b. Grade B milk is considered a manufacturing grade.


G. Classification is used for pricing systems. Producers may participate in the Market Order

Program, which establishes prices according to milk uses.

1. Class I milk is the highest price class and is used for fluid milk products.

2. Class II is used for soft milk products like yogurt, cottage cheese, and ice cream.

3. Class III is used for hard cheeses. 4. Class IV is used for butter and for milk

products in dried form.


H. Milk products will contain a sell-by date on the finished product package. This refers to the last date on which the product can be

offered for sale. I. When the product has completed all of the steps

in processing, pasteurization, standardization, homogenization, and quality control, it is packaged into gallon, half-gallon, quart, pint, and half-pint containers. These containers are kept below 40°F (4°C) in storage

warehouses where they are stored for a short period of time and then shipped to supermarkets.

How do you evaluate milk samples for flavor and odors? How do you critique milker head units for defects?

The flavor, scent, and visual inspection of milk are important to the overall quality and can be affected by the cow’s health, consumed feed, bacteria, chemical changes, or absorption of foreign flavors after processing.

The process of judging and scoring milk and other milk products is consistent throughout processing.

Milk is checked for irregularities at various points, including storage.

Dirty equipment can impact the results, so sanitation is critical.

These quality control practices ensure safe, healthy, and delicious milk products.


A. Determining problems 1. An off-flavor can be found by smelling

the open container rather than a small sample.

2. The next step involves tasting the milk. Samples should be at room temperature. The colder the sample, the harder it is to

distinguish certain flavors. The major flavor defects are bitter, feed, flat-

watery, foreign, garlic/onion, high acid, malty, oxidized, rancid, salty, and unclean.


B. The cleanliness of milking machine parts can influence the milk flavor.

These are the possible defects of rubber parts: 1. Dirty or milk stone—These parts have evidence

of gray and/or chalky soil or light films of soil. 2. Checked or blistered—These parts have been

used too long and have been poorly cleaned. 3. Leaky parts—These parts will allow air into the

system due to holes in air hoses. 4. Poorly fitted parts—These parts are obviously

not designed to fit and may include split hoses or broken hoses that are too short.


C. These are the possible defects of metal parts: 1. Dirty or milk stone—These parts show evidence

of soil or chalky material. 2. Badly dented or damaged—These parts have

damage that is sufficient enough to interfere with the function of the parts and with cleaning/sanitizing them.

3. Pitted or corroded—These parts have evidence of rust and darkened surfaces.

4. Open seams—These parts have evidence of broken joints, heads, or screws.

What are the steps in the cheese-making process? What are the four groups of cheese?

The varieties of cheese are based on ingredients, processing steps, and characteristics of the finished product.

A. Cheese can be made from a combination of fluid milks. Cottage cheese is made from skim milk;

Swiss cheese is made from a mixture of whole and skim milk; and cheddar cheese is made from whole milk.

B. Cheese is made by removing most of the milk solids from the milk through a process called coagulation or curdling. Curdling is the process that causes the milk to form into

curd—the part of milk that coagulates when milk turns sour or is treated with enzymes.


1. First the milk is heated. Then a liquid starter culture is added. The bacteria from the culture will form acids in the milk,

causing the milk to sour. 2. Rennet is added to force the milk to thicken.

It contains the enzyme rennin and is found in the stomachs of young calves.

Other enzymes may be used in the process. After the mixture is stirred, the curd forms.

The curd is separated from the whey (the watery liquid part of the milk mixture in the cheese-making process) by heating and draining it.


C. The next step may involve texture of the curd. This step is also called cheddaring;

it helps to force out more whey and allows for fermentation to continue until a desired pH level is reached.

D. Dry salt or brine is used next to achieve a desired flavor. For example, the curd of mozzarella is formed

into laves and placed into a brine, salt-water solution.

E. Cheese is formed into blocks.


F. The ripening or curing of cheese is exposed to a temperature/humidity controlled environment for a specified duration. Different types of cheese require months or

years to age. The changes that occur during the curing/aging

process depend on the enzymes, bacteria, mold, yeast, or combination of these agents.

G. After the cheese has met the desired age, it may be cut, packaged, waxed (if necessary), and put into blocks.


H. Cheese can be grouped as very hard, hard, semi-soft, or soft. The type of cheese depends on the kind of milk

used, the methods used in the coagulating of milk, the cooking and forming of the curd, the type of culture used, the salting method, and the ripening conditions.

A soft cheese, like cottage cheese, is an unripened cheese with 80 percent moisture.

Parmesan and Romano are very hard cheeses (grated or shaker cheeses).

How do you identify samples of cheese? Cheese identification should be

based on body, texture, color, and flavor.

A. Body refers to the physical properties. Observing and feeling the firmness,

cohesiveness, elasticity, and plasticity will help to determine and describe the appearance.

B. Texture refers to how the cheese particles are bound together. Open textures show spaces between the

particles; in contrast, closed textures show very few openings.

How do you identify samples of cheese? C. Color can range from a cream or off-

white to a light or heavy yellow. The color should only act as a guide

when identifying cheese. D. Flavor is the final factor.

The use of taste and smell help to distinguish the cheese types.

Cheeses have specific scents. Noting the odors and tasting small pieces will

assist in identification.

What are the steps of the yogurt-, sour-cream-, and cottage-cheese-making processes?

Yogurt, sour cream, and cottage cheese products are handled under controlled conditions.

These products require the addition of bacteria cultures to fluid milk for fermentation to occur.

These bacteria cultures will convert lactose into lactic acid.

The fermentation process and the specific bacterial culture used will determine the end product.


A. Yogurt products may use whole milk, low-fat milk, or skim milk, depending on the type of product desired. Yogurt must contain at least 3.25 percent milk fat. Low-fat yogurt allows up to 2 percent milk fat, and nonfat

yogurt allows less than 0.5 percent milk fat. Stabilizers (e.g., alginates, gelatins, and starch) are used

to improve the body and texture by increasing firmness and preventing whey separation; they also help to keep the fruit in yogurt uniformly mixed.

Flavors, sweeteners, and fruit may be added to yogurt for variety.

Bacterial cultures are used to ferment lactose so lactic acid results, producing the characteristic yogurt flavor.

What are the steps of the yogurt-, sour-cream-, and cottage-cheese-making processes? The general steps in the yogurt-making process

are listed below. 1. The milk composition should be adjusted and the

ingredients blended. 2. The milk mixture should be pasteurized. 3. Homogenizing the milk ensures that all of the

ingredients are thoroughly mixed. 4. The product is cooled at 108°F (42°C)—the ideal

growth temperature for a starter culture. 5. The product should be inoculated with a starter culture

and mixed into the cooled milk. 6. The product is then held at 108°F (42°C) until a pH of

4.5 is reached. 7. The yogurt is cooled to 44°F (7°C) to stop the

fermentation process. 8. Fruit and flavors are added. 9. The finished product is ready for packaging.


B. Sour cream can be offered as regular, reduced-fat, or nonfat. Regular sour cream contains at least 18

percent milk fat and is made from light cream. Reduced-fat sour cream contains at least 25

percent less milk fat than regular sour cream and is made from half-and-half.

Nonfat sour cream contains no more than 0.5 grams of milk fat per serving.

Sour cream may be cultured or acidified light cream.


Steps to culture sour cream are as follows: 1. First, the culture (Streptococcus lactis) is

added to pasteurized light cream. 2. Then it is incubated at 72°F (22°C) until

the desired flavor and the desired thickness are reached.

3. Additional nonfat milk solids and stabilizers are added, as needed.

What are the steps of the yogurt-, sour-cream-, and cottage-cheese-making processes? C. Cottage cheese is considered a fresh, unripened, soft

cheese with a mild and slightly acidic flavor. Four types of cottage cheese exist: creamed

cottage cheese, low-fat cottage cheese, nonfat cottage cheese, and baker’s cheese.

The following are steps in the creation of nonfat cottage cheese: 1. A bacterial culture or food-grade acid (vinegar) is added to

pasteurized milk. This causes the separation of the milk solids from the whey. 2. The curds are formed and gently cut into pieces that allow

the whey to be drained. 3. The curds are cooked and pressed to force out more whey. 4. The curds are rinsed, and salt is added. 5. Light cream dressing is added to achieve the desired finished

product.

What are the steps in the butter-making process? What are the types of butter? Butter is made from pasteurized cream and

comes in several types. A. Making butter involves several steps.

1. The cream is churned or shaken until the milk fat/butterfat is separated from the buttermilk.

2. After churning, the butter is rinsed and salted (if desired). 3. The excess buttermilk is removed.

B. There are several types of butter products. 1. Traditional butter is made from a sweet cream (also known

as pasteurized cream), has salt added for flavor, and acts as a preservative.

2. Unsalted butter is also available. 3. Whipped butter is another product. 4. Clarified butter is made from regular butter; however, the

water is evaporated as it is heated slowly. 5. Cultured butter is produced from a churned cream that has

been soured by a lactic acid culture.

What are the marketing options for dairy products?

Even though the dairy industry is probably best known for milk production, several additional items are used to generate dairy farm income.

A. Milk production is important to the economy because milk is used in many products. In terms of nutrition, milk is one of the least expensive

products. B. Veal is the meat of young calves that are not

used for replacement animals in the dairy herd. C. Beef is the meat from cattle. D. Cattle byproducts are products made from

various cattle parts.

What is the difference between real and artificial dairy foods? Many foods are made as imitation or substitute

products, and these products do not contain the same nutrients as the real products.

A. The main difference in imitation dairy products is the lack of real milk as the base product.

Imitation dairy products can be found in: 1. Cheese—Colby, cheddar, cream, mozzarella, and

American pasteurized processed cheese 2. Butter 3. Cream 4. Whipped cream 5. Sour cream 6. Ice cream 7. Milk

What is the difference between real and artificial dairy foods?

B. Imitation or artificial foods do not provide the nutrients of the traditional products. 1. These products are inconsistent because the

ingredients can be changed whenever desired by the manufacturers.

2. These products lack milk as the base product. 3. When comparing the food labels of real versus

artificial dairy food products, it is crucial to look for the REAL seal.

Examples of real versus artificial are the following: half-and-half coffee cream versus nondairy creamer, whipped cream versus whipped toppings, cheese versus vegetable cheeses, and butter versus margarine.

Review What are the steps involved in processing

milk? What are the types of milk? How do you grade and classify milk?



Review How do you identify samples of cheese?


What are the steps in the butter-making process? What are the types of butter?

Review What are the marketing options for dairy

products?

What is the difference between real and artificial dairy foods?