MILK PRODUCTS

By Millie Reynolds

What is Milk?

Milk is the opaque solution secreted by the mammary glands of all mammals for a period of time after giving birth to provide food for their young.

Most of the milk consumed by humans is cow's milk. However, a considerable amount of milk consumed in India, China, Egypt, and the Philippines comes from buffalo. In Mediterranean countries and to a lesser extent in many other countries, people also use goat's milk. In Northern European countries reindeer milk is used for food while in southern parts, sheep milk is used.

Milk is called an almost perfect food. It has of many nutrients that contribute to the overall nutritional requirements of our body. In our diet, milk is notable for its contribution of minerals calcium, phosphorus and complete protein.

Calcium is the most abundant mineral in our body. Not only does it give strength to our bones, calcium is found in practically every cell of our body. Our bones are a bank for calcium and if there is a shortage of calcium elsewhere in the body, calcium is borrowed from the bones. A persistent shortage of calcium can result in osteoporosis, a condition where bones are so porous and fragile they can easily break. Osteoporosis affects one in four women and one in eight men.

Composition of Milk

Milk contains water, protein, fat, sugar (lactose) and minerals. The proportion in different animals varies. Animals that grow rapidly have milk that has a higher proportion of protein and minerals while animals that need a thick layer of insulating fat have milk that has a higher proportion of fat.

Composition of Various Milks

Source	Water %	Protein %	Fat %	Sugar %	Minerals %
Human	87	1.1	3.8	6.8	0.2
Cow	87	3.5	3.7	4.9	0.7
Goat	87.9	3.5	4.3	4.3	0.9
Sheep	82	5.8	6.5	4.8	0.9
Indian Buffalo	82.7	3.6	7.4	5.5	0.8
Chinese Buffalo	76.8	6	12.6	3.7	0.9
Egyptian Buffalo	82.1	4.2	8	4.9	0.8
Reindeer	63.3	10.3	22.5	2.5	1.4

Milk Protein

Milk contains many proteins. The main milk protein is casein. It is not precipitated by heat but acid causes it to coagulate or curdle. Milk that sours curdles because lactic acid has been formed. Kitchen ingredients such as tomatoes, vinegar and citrus fruits are acid and will cause milk to curdle. Thickening the milk with flour or corn starch before adding the acid ingredient lessens the chances of milk curdling.

In cheese making, the enzyme rennin causes the casein to curdle and the curd is separated from the liquid whey. Water-soluble proteins stay in the whey. The cheese making process is continued with the curd.

Casein is used in the manufacture of paper, plastics and glue.

Another protein, lactalbumin, is affected by heat and sticks to the sides and bottom of the pan.

Milk Fat (Cream or Butter Fat)

The fat is made up of fatty acids, phospholipids, cholesterol and fat-soluble vitamins such as A, D, E, and K. Fat contributes to the milk's taste and texture. When the fat is removed from milk, so are the fat soluble vitamins. Vitamin A, which is a nutrient not an additive, is added to all forms of skim, 1%, and 2% milk. Vitamin D is added to fluid, powdered and evaporated milk. Our body needs Vitamin D to help absorb calcium in milk. Vitamin D, with the help of sunshine, is formed in the skin. Since there is a shortage of sufficient sunshine in the winter months and the vitamin is not found in many foods, it is by law added to milk.

Different breeds of cows produce different amounts of fat in their milk. Cows produce more fat in their milk in the winter, at the end of milking, and at the end of their milk producing period.

The federal government stipulates the amount of fat present in dairy products. Whole milk must have 3.2% fat; skim milk has a trace, whipping cream has 35%.

When whole milk sits, the fat globules will rise to the top. The fat could be "skimmed off" and used. Consumers did not like this, and so a process called homogenizing was developed.

Cream can be beaten and made into whipped cream. If the beating continues, the fat globules will stick together and form butter. A liquid, buttermilk, is separated from the butter.

Milk Sugar

The milk sugar is called Lactose. In digestion our body breaks it down into the simple sugars, glucose and galactose.

Lactose is dissolved in milk. It is relatively insoluble and so creates problems in manufacturing resulting in granular products. When powdered milk is reconstituted, leave it in the refrigerator for 2-3 days before using. This gives the sugar a chance to dissolve, thus improving the flavour of the milk. Bacterial action on lactose converts it to lactic acid and this is what makes milk sour and curdle.

Milk Cookery

• Milk scorches easily. To lessen the chances of scorching milk use a saucepan or a double boiler. Most milk recipes can be cooked in the microwave.
• Milk curdles with the addition of some foods. Foods with acid tomatoes, asparagus, string beans, broccoli, cabbage, lemons), salt (meats) and tannins. Lessen the chances of curdling by thickening the milk before adding the other foods and by adding the other food to the milk.

Milk Terminology

• Pasteurization is a process that effectively destroys all bacteria in milk whether it is helpful or disease causing bacteria. Most areas prohibit the sale of unpasteurized milk.
• Homogenization is a process whereby the large fat globules are reduced in size and stay suspended in the milk and do not float to the top. This makes the milk feel smooth and rich. Whole milk that is homogenized does not have cream floating on top as unhomogenized does.
• Whole milk is defined in the Milk Act as milk that contains at least 3.2% milk fat.
• Partly skimmed milk has a portion of the milk fat removed The most common partly skimmed milk contains 2 % fat and is called 2% milk; 1% milk contains 1% fat.
• Skim milk refers to milk that has had virtually all fat removed. The level of milk fat in skim milk is about 0.1%.
• Flavoured milk is milk to which a flavour is added. Examples are chocolate milk, which must contain at least 3 % milk fat, and chocolate partly skimmed milk, which must contain greater than 0.3% and less than 3% milk fat. Chocolate or cocoa, a sweetening agent, and sometimes a small amount of salt, are added to whole or partly skimmed milk.
• Buttermilk has a tangy flavour, a smooth rich body and contains from 0.1% to 2% milk fat. It is produced from pasteurized skim milk or partly skimmed milk. A "culture" is added to give buttermilk its consistency and flavour.

All of the above milks are pasteurized which greatly improves milk's "keeping" quality by effectively destroying disease-producing bacteria. The process makes cows' milk safe to drink yet does not affect the quality or quantity of the nutrients present in fluid milk.

• Evaporated milk is available in 7.5%, 2% and skim milk. It has a darker colour than the original milk because at high temperatures used to make this milk, a browning reaction occurs between the milk protein and the milk sugar. The milk is prepared by removing 60% of the water by evaporation. It is then homogenized, cooled, canned and sterilized.
• Sweetened condensed milk is made by condensing milk to 1/3 of its original volume and then adding sugar. This results in a thickened product. It contains about 40% sugar, a minimum of 8.5% milk fat and 28% total milk solids.
• Powdered milks (whole or skim) have about 3% water content. Most powdered milk is made by the spray-dry process. Partly evaporated milk is sprayed into a heated chamber where it dries instantly. The resulting powder is then cooled, sifted and packaged.
• UHT milk (ultra high temperature milk) is whole or partly skimmed fluid milk heated to 100 degrees C or more for two to three seconds before or after packaging. This inactivates both disease causing microorganisms and those that might be capable of reproducing and spoiling milk under non-refrigerated conditions. UHT milk can be found in most grocery stores in or close to the dairy section. It does not have to be refrigerated until the package is opened. Unopened, it keeps for three months with very little change in flavour and quality. Once opened, the milk should be refrigerated and used within one week.
• Lacteeze and LactAid are lactose-reduced milks available in 2% or skim. They are suitable for individuals who are lactose intolerant. Lactose-intolerant individuals do not have adequate amounts of the enzyme lactase to digest the milk sugar lactose. Upon drinking milk they may experience bloating, gas and diarrhea.

The milk is treated with a lactase enzyme, which breaks down the lactose in milk into simple sugars - galactose and glucose. Both LactAid and Lacteese are 99% lactose free and, therefore, are more easily tolerated. Lacteese and LactAid can be found in most grocery stores next to regular milk. Lactaid drops are also available, and can be added to regular milk to reduce the lactose content. Lastly, enzyme pills are also available. These pills when taken prior to consuming a milk product will help break down the lactose in the milk.

Alternate Milks

Goats' Milk - Most of the key nutrients in goats' milk compare favourably with cows' milk, with a few exceptions. Vitamin D and folic acid are generally much lower in goats' milk. Enrichment of whole goats' milk with vitamin D and evaporated goats' milk with vitamin D and folic acid is voluntary.

Soybean Milk - In comparison to cows' milk, milk made from soybeans contains lower amounts of protein, and much lower amounts of Vitamin A, folic acid, riboflavin and calcium. In fact, one cup of soybean milk only offers 10 mg of calcium compared to more than 300 mg of calcium in cows' milk.

Source: Saskatchewan Dairy Foundation

Dairy Products

Butter - Cream is churned and the fat globules come together and form globs of butter and a liquid called buttermilk. The butter is removed and washed. You can purchase salted or unsalted butter. Whipped butter may be available.

Whipping cream - has at least 30% fat.

Coffee cream - has at least 18% fat.

Sour cream - a culture is added to the cream. Cream used to be soured by letting the natural bacteria produce acid and sour the cream.

Buttermilk - a culture is added to milk. Buttermilk used to be the liquid that remained after butter has been churned and removed.

Yoghurt - a culture is added to milk and a thickened custard-like product develops. Fruit and flavourings may be added.

Chocolate flavoured drinks - prepared by adding sugar and cocoa to milk.

More information on milk is available in these pamphlets:

Canadian Milk Products - information on milk production and government specifications to ensure highest quality products.

Cows and the Environment - questions people commonly ask concerning whether raising cows for their milk is harmful to the environment.

Milk Products: Food for Life - commonly asked questions about milk.

Milk Allergy and Lactose Intolerance - information on milk allergy and intolerance and tips on introducing milk into your diet.

Myths and Misconceptions - answers some questions people have about milk and milk products.

Myths and Facts about Milk and Milk Products - discusses myths and explains the misconception.

Calcium for Life - discusses our body's need for calcium and food sources of calcium.

More information about milk or copies of the above pamphlets is available from:

Saskatchewan Dairy Foundation
Dairy Farmers of Saskatchewan
#2 - 425 Winnipeg Street, Regina, SK S4R 8P2
PHONE: 306-949-6999, FAX: 306- 949-2605,
EMAIL: sdf.cronk@sk.sympatico.ca

OR

Dairy Farmers of Canada
1801 McGill College Avenue, Suite 1000
Montreal, QC H3A 2N4
PHONE: 514-284-1092 FAX: 514-284-0449
Or Web Site: www.dairybureau.org