Dairy Foods for Everyone

Every family member's daily need for dairy foods is very explicitly outlined in the authoritative Canada's Food Guide. As one of the four important groups of foods, it is an essential part of good nutrition for everyone. Milk and milk products are important choices in each day's food selections, and contribute significant amounts of the nutrients essential to good health.

INFANT

The value of milk as a food for infants is unquestioned. It is usually the chief source of complete protein, calcium, vitamin A, thiamin, riboflavin, niacin, essential fatty acids, and energy for the rapidly developing child. Milk's physical and chemical properties are ideally suited for the infant's needs.

When mother's milk is not available, the physician usually prescribes a formula based on some type of cow's milk, modified with water and sugar to make the protein and carbohydrate content more similar to human milk. Either a formula prepared in the home or a commercially prepared formula may be used. If these formulae are not tolerated, some other type of manufactured formula may be prescribed.

Formulae made from cow's milk contain insufficient amounts of iron and vitamin C. That is why physicians may prescribe a supplement to be added or given separately to ensure that essential nutrients are provided immediately after birth. Evaporated milk is fortified with vitamin C and is often used for formulae.

The transition from formula to fluid milk and solid foods is a gradual process that most infants accomplish sometime between 6 and 12 months of age.

CHILDREN

During the preschool years, the soft, bland diet of infancy gradually undergoes a change. The preschool child learns to eat foods with a variety of flavours and textures and begins to establish food habits which may permanently influence future nutritional status. Children's meals should include all foods listed in Canada's Food Guide and milk and milk products should continue to play an important role.

In the second year of life, a child's rate of growth slows, and appetite decreases. Although energy needs in relation to body weight are lower than in infancy, a continuing supply of high quality protein (plus other growth-promoting nutrients) are required. Throughout preschool years, although the child's bones and teeth will develop at a slower rate than earlier, substantial amounts of calcium, phosphorous and vitamin D are still needed.

Milk plays an important role in supplying these nutrients, even though a child's decreased appetite may mean that he or she is drinking slightly less than the recommended amount of milk (2 to 3 servings). Food made with milk, such as cream sauces, milk puddings and custards, can be included at meals to assure the required intake. Also products such as yogurt, cheese and ice cream can be introduced in the preschool years.

The school age child's rapid rate of growth, with corresponding increase in appetite, demands more food to meet body needs. Again, dairy foods makes a significant contribution in terms of calcium, riboflavin and high quality protein, plus other nutrients. In fact, it is virtually impossible for the average Canadian child to obtain the amount of calcium needed, unless he or she receives the recommended allowance of 2 to 3 servings of milk and milk products each day. A continuing supply of vitamin D is just as essential at this stage of growth as during earlier years. Children can readily obtain it from fortified milk.

PRETEENS AND TEENS

A youngster's rapid growth and development during prepubertal and pubertal years brings about a marked increase in all nutrient needs. Requirements for energy, vitamins and high quality protein (such as that found in milk, meat and eggs) are greater, and the needs for calcium and iron are at a higher level than at any other period of life, except during pregnancy and lactation. An adequate intake of all essential nutrients is assured when the teenager's meals include the variety and recommended amounts of foods outlined in Canada's Food Guide.

When this age group include, in their daily diet, 3 to 4 servings of milk and milk products, they obtain generous amounts of many essential nutrients, particularly calcium, riboflavin, niacin and protein. The vitamin D needed by these growing young people is also provided from the recommended intake of fortified milk.

Some adolescents, whose eating habits were good as children, succumb to fad diets and unusual food practices during their teen years. Changes in food patterns may reflect a desire to assert independence and to exert authority in food selections. They try to copy a peer group, or to achieve certain goals related to their figure, skin, general fitness and appearance.

Whatever their meal patterns, teenagers should be encouraged to include at least 3 to 4 servings of dairy foods each day. Servings can be in the form of milk shakes, flavoured milks, yogurt, icecreamm or cheese as well as fluid milk. Those who are calorie conscious should be advised to select all foods with care to ensure an adequate supply of essential nutrients. Skim and partly skimmed (2%) milk, with their high ratio of nutrients to total kilojoules, are among the foods best suited to controlenergyy intake.

The teenage girl should take special care to get the necessary amounts of calcium, protein, vitamins A, D, C and riboflavin, any or all of which are often too low in teenage diets. Good food habits during her teen years will help her build a healthy body so that she may bear healthy babies. At the same time, she should gain the knowledge needed to select proper foods for her future family.

Most teenage boys have better appetites than teenage girls; as a result, they are most likely to eat nutritious meals. In addition to their greater body size, boys tend to be more active, and take part in more athletic activities than girls. Thus, their energy needs are higher and their energy requirements greater. The need for most essential nutrients for both boys and girls does not decrease until they stop growing during their late teens or early twenties. In young adulthood, their food choices are still most important. Milk and milk products can serve them well and provide an easy solution to many of their nutrient needs.

ADULTS

The adult requires the same nutrients as the child or adolescent, but in different proportions. His needs are for maintenance of health and vigour, rather than for growth and development. Energy requirements are usually less, depending upon daily work and activity. At any age, the body must have a constant supply of calcium. Recent studies suggest that even moderate calcium deficiencies over a prolonged period may lead to bone fragility (osteoporosis) in later years.

When milk and milk products are not eaten during adult years, the body may have to deplete the bones (the calcium "bank") to obtain the needed amounts of this essential nutrient. The average adult can obtain the necessary calcium intake by including the recommended 2 servings of milk and milk products in the daily diet. These foods will also provide generous amounts of protein and riboflavin, two other important essentials for the healthy, active adult. Skim or partly skimmed milks are good food choices for weight watchers.

PREGNANCY AND LACTATION

The expectant mother should be guided from the early stages in her selection of foods by a physician who is aware of her general health and the progress of her pregnancy. Studies indicate that the food she eats affects the course of pregnancy, the health of the newborn infant, and the mother's ability to nurse her baby. The teenage mother must give particular consideration to her daily meals, since the extra requirements of pregnancy are superimposed on her own nutritional needs as she completes normal growth and reaches maturity.

In human development, the most rapid rate of growth occurs in the unborn infant. An increased supply of several nutrients is required after the first three months, both for the developing fetus, and to build up the mother's reserves in preparation for childbirth and lactation. If the mother has been well nourished before her pregnancy, the increased recommended allowances will be adequate to protect her health and that of her unborn baby. Otherwise, dietary improvements should begin as soon as she is aware of her condition.

Calcium and phosphorous are needed for the formation of bone and tooth structures throughout pregnancy. Although most of the deposition of these minerals in both bones and teeth take place during the last trimester of pregnancy, the infant's first (baby) teeth begin to form early in prenatal life. To meet these extra requirements, additional calcium is recommended during the second and third trimesters, even though absorption of dietary calcium improves during pregnancy. The recommended increased milk and milk products at this time contributes the additional calcium and phosphorus needed, and simultaneously provides extra protein needed for development of the fetus, and for formation of new maternal tissues. The vitamin D required to ensure proper utilization of the minerals can be obtained from fortified milk or from a vitamin supplement prescribed by the physician.

Dairy foods continue to play an important role in the mother's meal pattern after her baby is born, particularly while she is nursing the child. Although lactating women are advised to include about the same amount of dairy foods in their daily meals as pregnant women (3 - 4 servings), the new mother's needs for some nutrients are increased during the lactation period. Extra protein, B vitamins, and vitamins A and C are particularly important, while her requirements for calcium, iron and vitamin D are the same as during pregnancy.

SENIOR SET

Our senior citizens must continue their respect for good nutrition if they wish to enjoy healthy later years. Fundamentally, the older adult's nutrient needs are very similar to those of younger persons. Less physical activity results usually in decreased energy needs to avoid obesity and its complications. Inadequate mastication of food, decreased appetite, and less efficient digestion, poor absorption and utilization of nutrients, may also accompany the aging process. Canada's Food Guide is recommended as a most reliable guide for senior citizens who wish to continue a healthful eating pattern.

The excellent nutrient content of dairy foods, with comparatively moderate energy value, makes them important food choices for this age group. Older persons who do not enjoy drinking milk can benefit from its food values by using it in food preparation, or by eating cheese, ice cream, yogurt, and other dairy foods. These are sources of easily-digested, high quality protein and fat, plus a variety of other essentials, including the calcium needed to protect against demineralization of the skeleton, which often results in osteoporosis.

THERAPEUTIC NUTRITION

Dietary management has become increasingly important in the treatment of disease and subnormal health. Many families must plan and serve meals, suited to a modified eating pattern, recommended by a physician for one or more members of that family. With very few exceptions, the restrictions or scientific modifications imposed do not affect the amounts of milk or dairy foods used. In fact, milk often becomes the most important food because of its generous contribution of essential nutrients, its ease of digestion, and its convenient form. Where fluid or soft diets are indicated, milk and foods made from milk are usually the basis of the day's meals or feedings. Modified milks are widely used when extra protein is required. In diabetic and weight control diets, milk and dairy foods are important parts of the total daily eating pattern.

KINDS OF DAIRY FOODS

Modern technology has made it possible for the dairy industry to offer a wide variety of products to Canadians. Research into these products continues in an effort to satisfy the preferences of consumers; to find effective use of surpluses, and by-products; to facilitate better storage, distribution and marketing methods; and to maintain even higher standards of quality. The pages which follow describe the characteristics of most types of dairy foods available in Canada, and outlines the latest methods for processing them.

PASTEURIZATION

Milk to be used for fluid purposes or in the manufacture of most dairy foods is pasteurized. There is still a small demand for raw milk cheddar cheese; however, bacteria are destroyed during the cheese manufacturing process.

Pasteurization is one of the most important steps in processing milk. It greatly improves milk's "keeping" quality by effectively destroying virtually all disease-producing (and most other) bacteria. It does not affect the quality not the quantity of calcium, protein, riboflavin and vitamin A present in fluid milk, but some vitamin C and thiamin are destroyed at the high pasteurization temperatures.

Fluid milk sold in Canada is usually pasteurized by one of two methods. The most modern, used by the majority of dairies, is known as "High Temperature Short Time"(HTST) pasteurization. Milk is heated to not less than 72 C and held for not less than 16 seconds; then cooled rapidly to 4.44 C. For maximum flavour retention, large dairies report that pasteurization temperatures do not exceed 79.4 C. The other method, used in small plant operations, involves heating the milk to a least 62.7 C holding it for not less than 30 minutes, then cooling it rapidly to 4.44 C.

Raw milk is not recommended. However, in homes or communities where raw milk is available, health authorities strongly advise home pasteurization. Milk should be heated to the verge of boiling, then cooled rapidly.

HOMOGENIZATION

Homogenization involves pumping milk, under pressure, through very small openings, breaking the fat into minute globules which are immediately surrounded by a film of protein that prevents them from reuniting. Because the new emulsion is more stable, a cream layer does not form upon standing (even after 48 hours of storage). When whole milk is not homogenized, it is referred to as standard or cream-line milk because the lighter fat globules rise and form a distinct cream layer.

FRESH FLUID MILKS

Standards for composition of milk are established by the provincial Departments of Agriculture to keep milk's ingredients constant, since they vary with the individual cow, the breed of cow and the season.

Milk is standardized at the processing plant to meet or exceed the minimum legal requirement by pooling it from several farms. Most communities in Canada require that milk sold to the consumer be pasteurized and be so labelled.

WHOLE MILK is defined in Canada as milk that contains at least 3.25% milk fat and at least 8% non-fat non-fat milk solids. Most fluid whole milk marketed is homogenized.

When part of milk's fat is removed, it is called PARTLY SKIMMED MILK, partially skimmed milk or low fat milk, depending on the area of Canada in which it is sold. Standards for fat content vary from 0.17 to 3.2 % milk fat, but the most common product contains two percent fat and is called 2 % milk. All partially skimmed milk is homogenized.

SKIM MILK, or skimmed milk, usually refers to milk which has had most of the fat removed. The minute level of milk fat in skim milk is about 1 %.

STERILIZED MILK (UHT milk) is milk which has been heated to a temperature of 100 C to destroy all organisms present and is packaged in hermetically sealed containers. It contains not less than 3.25 % milk fat.

CREAMS

CREAM is made by separating standard milk into skim milk and cream containing about 40% milk fat. This concentrated cream is diluted with milk to obtain fat levels as follows: CEREAL CREAM (light cream) may contain 8 to 15.9 % fat, but is usually 10% fat by weight; HALF AND HALF contains 8 to 15.9 % fat, but has about 11.5% fat and has 8 to 15.9 % non-fat solids; TABLE CREAM, often called "cream", usually is 18% but may have 16 to 31.9% fat; WHIPPING CREAM usually contains 35% fat, but ranges from 30 to 35%, and when packaged in aerosol cans it may range from 18 to 26 %.

Food and Drug Regulations permit a "pH adjusting agent" in fresh cream, and if indicated on the label, a stabilizing agent such as sodium citrate. The stabilizer helps prevent the feathery flakes that may form when cream is added to hot liquids.

STERILIZED CREAM is homogenized cream heated to 140.5 C and held, under pressure, at that temperature for 2 seconds. It is then cooled rapidly to 70 C, the pressure released, cooled again to 15.6 C and packaged aseptically. It is then cooled to 4.44 C. Unopened, this cream will keep for several weeks at room temperature. Once the package is opened, the cream must be refrigerated.

SPECIALLY PROCESSED MILKS

FLAVOURED MILKS are milks which a flavour is added. Examples are CHOCOLATE MILK which must contain at least 3% milk fat, and CHOCOLATE PARTIALLY SKIMMED milk which must contain greater than .1% and less than 3% fat. Chocolate or cocoa, a sweetening agent, and sometimes salt, are added to whole or partially skimmed milk.

MODIFIED MILKS are identified as skim milk and partially skimmed milk with added milk solids containing not less than 10% milk solids. Skim milk powders and/or evaporated milk are used to provide milk solids.

SOME BEVERAGES MODE FROM A MILK BASE do not qualify as milk under Food and Drug Regulations. They are non-standardized products. Examples include powdered chocolate beverage, eggnog and instant breakfast.

CONCENTRATED MILKS

POWDERED WHOLE MILK and POWDERED SKIM MILK are powdered milks with about 3% water content. Most powdered milk is made by the spray-dry process, in which partly evaporated milk is sprayed into a heated chamber where it dries almost instantly and falls as a powder ready for cooling, sifting and packaging. Powdered whole milk must be packaged in a vacuum as an extra precaution to prevent the oxidation of fat. To produce "instantized" skim milk powder that readily dissolves, the skim milk powder is blown into a chamber containing air saturated with steam, where the minute particles aggregate into larger particles containing many tiny air spaces. DRY BUTTERMILK, containing a maximum of 5% moisture and at least 4.5% milk fat, is processed primarily for commercial use.

EVAPORATED MILK, sometimes called CONCENTRATED MILK, includes EVAPORATED WHOLE, EVAPORATED PARTLY SKIMMED and EVAPORATED SKIM MILKS, depending on the type of milk used in its production. All have a darker colour than the original milk because at high temperatures a browning reaction occurs between the milk protein and the lactose. In processing, the milk is standardized to a desired ratio of solids to fat and forewarmed to prevent the casein from coagulating during sterilization. After 60% of the water is removed by evaporation, the milk is homogenized, cooled, restandardized, and canned. Then it is sterilized by heating for 10 to 15 minutes at 98.9 to 120 C. Controlled amounts of disodium phosphate and/or sodium citrate preserve the "salt balance" and prevent coagulation of the milk that might occur at high temperatures and during storage.

SWEETENED CONDENSED MILK is a viscous, sweet, cream coloured milk made by condensing milk to 1/3 of its original volume to which sugar has been added. It contains about 40% sugar, a minimum of 8.5% milk fat and 28% total milk solids. High temperatures of evaporation pasteurize the milk and its high sugar content acts as a preservative, making sterilization unnecessary.

MALTED MILK is a powdered product containing at least 7.5% milk fat and not more than 3.5 % moisture. Malt is added to whole milk and the mixture is dehydrated after the enzymatic action of the malt is completed.

CULTURED DAIRY FOODS

Cultured dairy foods are prepared by adding bacterial cultures to pasteurized or sterilized milk to convert the lactose into lactic acid, the citric acid into diacetyl; and to coagulate the casein. These products include YOGURT, SOUR CREAM (Salad Cream), BUTTERMILK and COTTAGE CHEESE.

YOGURT is a delicate, tangy product made from either whole milk, partly skimmed milk or skim milk (with skim milk powder sometimes added) to make a total of about 16% milk solids. Although it ranges from 1 to 3% milk fat, yogurt usually contains 2% fat. It is available as the plain milk product or with added flavourings (fruit or vanilla), fruit or fruit juice. Yogurt is made by heating pasteurized, homogenized milk to suitable temperatures and inoculating it with acid producing bacterial cultures. If a set custard type (a semi-solid consistency) is desired, the warm inoculated milk is put directly into consumer containers, incubated under controlled conditions, then cooled to less than 4.44 C. When these yogurts contain fruit, the fruit mixture is layered in the bottom of the container before the milk preparation is added. In making the stirred type (Swiss style), the vats of warm inoculated milk are incubated, cooled to less than 4.44 C and stored for up to 48 hours. Then it is stirred to a smooth, cream-like consistency and the fruit preparation is added. Yogurt has a storage life of 2 to 4 weeks when properly refrigerated.

YOGURT DRINKS are processed in a similar manner to yogurt to provide a tangy beverage. The fat content of the drinks varies according to the manufacturer.

SOUR CREAM has a delicate aromatic flavour and contains from 10 to 18% milk fat by weight. This cultured milk product is made by the same process as buttermilk, by ripening pasteurized cream with a lactic acid culture.

BUTTERMILK has a characteristic tangy flavour, a smooth rich body and contains from .1 to 2% milk fat. Originally, it was a by-product of butter-making. Today it is made by the culture method...the controlled fermentation of lactic acid and flavour-producing bacteria. Buttermilk is produced from pasteurized skim milk fortified with skimmed milk solids, or from partly skimmed milk to which milk fat is added in the form of homogenized cream. Milk is inoculated with the culture, incubated under controlled conditions until 0.8 to 0.9% acidity is reached; then cooled quickly to 10 C at which time salt may be added for flavour.

FROZEN DAIRY FOODS

ICE CREAM contains at least 36% total solids, at least 10% of which is milk fat in most flavours. In the case of added chocolate, fruit, nuts, etc., the amount of fat may be proportionately reduced to a minimum of 8%.

One of the most popular of a number of frozen dairy products, it is made from a mix, which is a combination of basic ingredients. These include cream, whole and/or condensed milk, and/or other milk solids, sugar (a portion of which may be corn sugar or glucose) and flavouring. A stabilizer of vegetable origin and an emulsifier, which together may take up not more than 0.5% of the mix, are also added. The mix is pasteurized, homogenized, flavoured if desired and then frozen rapidly to obtain a smooth, creamy product. During freezing, air is incorporated by whipping to provide the increase in volume (known as "overrun") that is essential for a light, desirable product. Most commonly the overrun is 80 to 110%. After packaging, ice cream is hardened at -31 C and held at -23.9 to -28.9 C during storage and distribution.

SOFT ICE CREAM, a smooth, compact product with at least 8 to 10% milk fat, has slightly more non-fat solids and 2 to 3 % less sugar than hard ice cream. The extra milk solids, the stabilizers and emulsifiers used, the overrun of about 40% and the serving temperature of -6.67 to 7.78 C, all contribute to its soft texture.

ICE MILK contains between 3 to 5 % milk fat and 33% total solids. Made from milk, it contains added milk solids, sugar and flavouring, and has an average overrun of 90%. In its soft form, it sometimes is sold as soft ice cream.

SHERBET is a tart flavoured product with a maximum of 5% total milk solids, and an overrun of 30 to 35%. Fresh of dried skim milk and milk fat, added to a base of syrup and fruit juice, constitute its basic ingredients.

FROZEN YOGURT, as the name implies, is a frozen version of yogurt. A stabilizer and flavouring may be added.

CHEESE

Many types of cheeses, both natural and process, are made in Canada. Several factors determine their distinctive flavour, texture and appearance: kinds of milk used, the method for setting the curd, the type of bacteria used in ripening, the temperature and humidity during ripening, the length of time the cheese is aged, and the amount of salt or other seasonings added. All natural cheeses are made from milk, cream or whey.

CHEDDAR is the most famous of Canada's natural-type cheeses and is produced in greater quantity than any other. Most Cheddars are made from pasteurized cow's milk, but the highest quality Cheddar is generally made from raw milk. The process involves heating the milk to 30.6 C, putting in a starter to promote the growth of lactic acid-forming organisms, then adding rennet to form the curd. The curd is heated to 37.6 C, then the whey is drained off and salt added. After cutting, the curd is compressed into large forms and held at 14.4 to 15.6 C for a least 8 days.

The cheese is reopened or cured at 4.44 to 10.0 C for varying lengths of time... one year for "old", at least 6 months for "medium" and at least 60 days for "mild" Cheddar. Sixty days is the minimum time required to destroy any harmful bacteria that might be present. During the ripening process, the characteristic Cheddar flavour and body are developed. The longer the ripening period, the sharper and nippier the flavour, and the softer the texture. When colouring is added, the cheese becomes a deep orange shade rather than its natural cream colour.

COTTAGE CHEESE, another natural type, is a fresh, soft, milk, white cheese. It is made by adding a lactic acid-producing starter, and a coagulator such as rennet, to pasteurized skim milk, either fresh or reconstituted. The resulting curd is cut and heated to develop texture and body, then the whey is removed and the curd is washed. Salt may be added.

Small curd and large curd cottage cheese are both sold either dry or creamed. In the latter, a blend of pasteurized cream and dry curd makes a product with a least 4% milk fat by weight. Fruits, vegetables, spices and herbs may be added.

QUARK, although similar to cottage cheese, is smoother, milder and less salty and contains not more than 7% milk fat.

CREAM CHEESE, also a fresh cheese, has a mild flavour and contains a higher proportion of moisture and fat than other natural cheese. It is made from cream, or a blend of milk and cream, with flavouring and seasoning often added for variety.

Whey cheeses, such as RICOTTA, are made by using heat and acid to coagulate the protein in the whey recovered from other cheese-making processes.

As well as the previously mentioned cheeses, there are over 50 additional natural variety cheeses made in Canada. Each has its own distinctive flavour and texture; all are manufactured under carefully controlled conditions. Some of these are: BRICK, BRIE, GOUDA, LIMBURGER, MOZZARELLA, PARMESAN, PROVOLONE, ROMANO, BLUE, COLBY and SWISS. OKA is a true Canadian classic cheese developed by the Trappist monks in Canada. It is semi-soft and has a full flavoured taste that's mellow, moist and creamy with a nutty tang.

PROCESSED CHEESES are a blend of natural cheeses. These are ground, melted and pasteurized, then blended with one or more optional ingredients: milk solids, water, colouring agents, seasonings, relishes, emulsifiers and preservatives. While hot, the semi-liquid mixture is poured into molds, jars or packages.

PROCESSED SKIM MILK CHEESE AND PROCESSED CHEDDAR CHEESE contains not more than 7% and not less than 31% milk fat respectively. COLD PACK CHEESE is made by mixing a variety of cheeses into a homogenous mass without the aid of heat.

CHEESE SPREADS AND CHEESE FOODS

CREAM CHEESE SPREAD must contain at least 51% cream cheese. It is somewhat higher in moisture and may contain less milk fat than cream cheese. Milk and milk products may be added to the spread.

PROCESSED CHEESE FOOD is a blend of cheeses with added milk or milk products. It is higher in moisture and may be lower in milk fat than process cheese but it must contain at least 51% cheese.

PROCESSED CHEESE SPREAD is similar to PROCESSED CHEESE FOOD but may have a higher moisture content and a lower milk fat content. The product must contain at least 51% cheese.

COLD PACK CHEESE FOOD is made like COLD PACK CHEESE and must contain 51% cheese. It contains not more than 46% moisture and not less than 23% milk fat.

BUTTER

Butter is a product made from cream. In addition to the minimum 80% by weight from fat, it contains milk solids, water, usually some salt (sweet butter contains no added salt) and colouring may be added. It is manufactured either by the churning method, or by the continuous method which gives butter a slightly different texture. Both methods use sweet, neutralized or ripened cream, pasteurized and standardized to a usual fat content of 30 to 40%.

QUALITY OF DAIRY FOODS

All dairy foods are made from milk which is produced to rigid government specification. The same emphasis on quality control is maintained in processing plants to assure Canadians that milk and milk products are at all times free from contamination.

High quality dairy foods are produced for Canadians through cooperative efforts of the dairy industry, the departments of health, the departments of agriculture and other government agencies. Each provincial jurisdiction has standards for dairy foods. In some cases, these are enforced by the province; in others, by federal agencies. In areas where the sale of raw milk is still permitted, it is subject to strict government control.

The retailer and the consumer also have a responsibility in the handling and care of dairy foods to maintain their high quality after they are processed. Protection from fluorescent light and sunlight, plus maintenance of refrigerated temperatures are essential. As the temperature of milk product rises, bacterial growth increases rapidly, with consequent formation of acid that characterized souring.

The best storage temperature for any dairy food is slightly above freezing. Proper care is essential: keep clean, covered, and cold; use within a reasonable length of time; protect from sunlight and fluorescent lights; once removed, do not return unused portion to original container.

COMPOSITION OF DAIRY FOODS

All dairy foods are made from milk, and their components are the same as those of milk but in varying amounts. Butter is an exception being comprised mainly of milk fat.

Milk is an oil-in-water type of emulsion (87% water), stabilized by complex phospholipids and proteins bound to the surface of the fat globules. It contains proteins in colloidal dispersion, lactose in true solution, minerals, fat-soluble and water-soluble vitamins, enzymes and other organic compounds. A unique liquid food, Its white appearance is produced by two salts, calcium caseinate and calcium phosphate.

PROTEINS

Milk's principal proteins are casein (about 80%) and the whey proteins called lactalbumin and lactoglobulin. These proteins are complete or high quality; that is, they contain in good proportions all the essential amino acids required by man. Essential amino acids are those that must be provided in food because the body cannot synthesize them at a rate sufficient to meet the needs for growth and maintenance. Most other animal proteins are also complete, but plant proteins are incomplete and have a lower biological value.

Cheese is also an excellent source of high quality protein. But since it does not contain whey proteins, its amino acid contribution differs from that of milk. Milk protein has a high coefficient of digestibility (87 to 90%). In addition, when combinations of foods are eaten at the same meal, milk's high quality protein complements the incomplete proteins. For example, milk contains lysine to supplement the amino acids in bread. Together these foods can present more amino acids in ideal proportions for protein synthesis in the body than either food by itself.

FATS OR LIPIDS

Milk fat is 95 to 96% triglycerides (esters of fatty acids with glycerol); 0.8 to 1.0% phospholipids; 0.2 to 0.4% sterol - chiefly cholesterol; traces of free fatty acids, waxes, and squalene (an intermediary of cholesterol), and varying amounts of all the known fat-soluble vitamins. The complex composition of milk fat includes at least 64 different fatty acids, containing from 4 to 26 carbon atoms with a relatively high proportion of short-chain, saturated fatty acids, many of which are not found in other fats.

In general, the fatty acids in milk fat are about 66% saturated, 30% monounsaturated and 4% polyunsaturated. Milk fat is a small but dependable source of the essential fatty acids. The linoleic acid in milk is in a form which favours conversion to arachidonic acid. These fatty acids are considered essential as the body is unable to manufacture them and therefore, must be supplied in the diet.

Milk's emulsified fat is more easily digested than any other food fat except that of eggs. Like other dietary fats, milk fat contributes to the satiety value of a meal and is a concentrated source of energy, providing 50% of whole milk's food energy.

Milk's phospholipids are bound to the surface of the gat globules along with proteins. These are substances containing phosphorus, nitrogen and fatty acids.

Cholesterol, the principal sterol in milk fat, makes up about 0.25% of the total fat. Currently there is much scientific controversy about cholesterol, although it is known to be indispensable to the body's normal function. It serves as a precursor for many biologically important steroid sex hormones and much (80%) of the cholesterol metabolized is converted to important bile acids.

The body obtains cholesterol, both by an internal synthesis, and from outside food sources.

CARBOHYDRATES

Milk is the only food source of the carbohydrate lactose, although it is the only significant carbohydrate in milk; traces of others, such as glucose and glucosamines, are also present. Lactose, a sugar, provides half of the total solids in milk and contributes 30% of the food energy in whole milk.

Lactose has many beneficial characteristics. A relatively low solubility makes it less irritating to the stomach and intestinal mucosa than highly soluble sugars. Lactose stimulates the growth of intestinal micro-organisms that synthesize the B vitamins...biotin, riboflavin and folic acid. It produces organic acids which provide an ideal protective medium (especially for infants and very young children) by checking the growth of undesirable bacteria in the intestine. In addition, lactose increases the absorption of calcium, phosphorus and magnesium, and favourably affects the intestinal flora. Cheese and yogurt are low in lactose, as the lactose is converted to lactic acid by a bacterial culture necessary to make these products.

MINERALS

Milk contains some of all the minerals known to be needed for good nutrition. Its mineral ash contains calcium, phosphorus, magnesium, potassium, sodium, chlorine, sulphur, and others in trace amounts. Calcium and phosphorus merit particular emphasis.

The distribution of CALCIUM in foods other than milk and dairy foods is not extensive. This is why studies have revealed calcium to be an essential nutrient often lacking in the diet.

The calcium in milk is readily available for utilization by the body because it is highly dispersed in the ionic form essential for absorption. The lactose present further favours this calcium absorption. Calcium is essential for normal bones and teeth; it also functions as a catalyst in several enzymatic reactions. Milk contains PHOSPHORUS in a readily utilized form and, in the calcium to phosphorus ratio, ideal for body use. There is an interdependence of calcium, phosphorus and vitamin D in the body, and all must be supplied simultaneously for efficient utilization. These three nutrients are involved in, and essential for, normal bone and tooth formation.

VITAMINS

Whole milk contains some of all the vitamins known to be required by man. Included are the FAT-SOLUBLE VITAMINS A,E, and K which are found in the fat phase of milk.

Whole milk contains significant amounts of VITAMIN A and its fat soluble precursor, carotene, that imparts its creamy colour. When fat is removed (as in 2% or skim milk), the vitamin A content decreases accordingly. The Food and Drug Act requires the addition of vitamin A to all skim and partly skimmed milks within the range of 1200 to 2500 IU for each 852 mL.

VITAMIN D is needed for the body's utilization of calcium and phosphorus. Most foods are extremely poor sources of the D vitamin. Since milk is a common food consumed by Canadians, it was chosen to be fortified. The Food and Drug Act requires the addition of 300 - 400 IU of vitamin D per 852 mL of milk. The vitamin D added is usually in the form of cholecalciferol(D3).

Both VITAMINE E, and antioxidant that prevents fat oxidation, and VITAMIN K, which is involved in blood clotting, are found in very small amounts in whole milk.

Milk in its liquid phase contains the WATER-SOLUBLE VITAMINS...ascorbic acid and the B vitamin group. Since they are synthesized by micro-organisms in the rumen of the dairy cow, their concentration in milk remains fairly constant.

Milk is an excellent source of RIBOFLAVIN. Little of this valuable nutrient is lost through pasteurization since it is stable to heat. Riboflavin is destroyed by ultraviolet light but these losses may be prevented by the use of opaque milk cartons and darkened refrigerators.

Although milk appears to provide a low level of NIACIN (nicotinic acid), it is a good source of the amino acid tryptophan, which can be converted to niacin in the body thereby giving milk a high niacin equivalent.

Milk also contains significant amounts of the heat labile B vitamin, THIAMIN. Its losses during pasteurization, drying and condensing are minimal when modern techniques are used.

Milk provides small amounts of the other B vitamins. PYRIDOXINE (B6) occurs in milk as pyridoxal, a biologically active agent. Essential for amino acid metabolism, it acts as a co-enzyme in transamination and in the conversion of tryptophan to niacin. PANTOTHENIC ACID is relatively stable in moist heat and little is lost during pasteurization. It is essential for all living organisms and is a constituent of co-enzyme A. Folacin (folic acid), necessary for normal blood formation, is found in very small amounts in milk. However, milk is one of the best sources of CYANOCOBALAMIN (b12), a vitamin directly related to the prevention of pernicious anemia; it is found only in foods of animal origin.

Milk is considered a good source of BIOTIN (even though it has only minute quantities) since only 40mg are needed each day to supplement that synthesized in the intestine. CHOLINE, which is involved in fat transport in the body, and INOSITOL, which may be involved, are also found in milk. Milk is not a major source of VITAMIN C. In order to meet the needs of formula fed infants who do not receive citrus fruit juice, the Food and Drug Act requires the addition of vitamin C to evaporated milk.

VITAMIN ENRICHMENT

Only milk for fluid, powdered or evaporated milk is required to be enriched with vitamins. Milk used for cheese, ice cream, yogurt, buttermilk is not enriched.

ADDITIONAL FACTS ABOUT DAIRY FOODS

Good news for ALLERGY SUFFERERS! People who are allergic to fresh, pasteurized milk may well ba able to drink evaporated milk without any problems. The physio-chemical changes in evaporated milk's protein caused by the high heat of processing, make it an excellent substitutes for some who may have reactions to other types of milk. In additon, the smooth, fine curd formed during processing makes evaporated milk easier to digest.

Is milk taboo for ATHLETES? Certainly not. It's a good reliable source of nutrients needed to give stamina and vitality for all out performance...a "must" food for well-conditioned athletes. Where else can they combine so many good nutrients as in a glass of milk!

Is CHEESE constipating? Not unless you overdo its consumption. Doctors agree that too much of any concentrated protein food, to the exclusion of other foods which normally provide necessary fibre can create problems for overworked organs in the lower digestive tract. The solution is variety. Choose cheese, along with foods from each of the other main groups in Canada's Food Guide, and build the day's menus around them.

There has been some confusing controversy over LACTOSE INTOLERANCE in recent years. However, after careful interpretation of the latest available data, it has been found that lactose intolerance does not necessarily mean milk intolerance. Even people who are clinically diagnosed as being lactose intolerant can usually drink 250 mL of milk at a time, especially with meals. Actually there are very few individuals who exhibit symptoms from recommended amounts of milk.

Are some FOOD COMBINATIONS dangerous? Not unless they're eaten on a rollercoaster! Persistent "old wives" tales linking digestive upsets, and even serious illness, with the practice of combining certain foods at the same meal (such as milk with oysters of fish, milk with cucumbers or tomatoes, buttermilk with cabbage or ice cream with shellfish) are superstitions that your doctor or nutritionist will confirm went out with the witches' brew. Most of these fables probably developed before the time of adequate home refrigeration and proper food handling techniques.