Milk fat

In milk fat, cholesterol is associated with Hpoproteins in the milk fat globule. It is also a component of animal membranes and controls rigidity and permeabihty of the membranes. Cholesterol has interesting surface properties and can occur in Hquid crystalline forms. Plants contain sterols such as P-sitosterol [83-46-5] (4b) or stigmasterol [83-48-7] (4c). Their functions in plant metaboHsm are not yet well understood. Analysis of sterols has proven useful for detection of adulteration of edible fats (9). 

Fat. Milk fat is a mixture of triglycerides and diglycerides (see Fats and fatty oils). The triglycerides are short-chain, C. —C., medium-chain, 24 46 ... 

Table 6. Fatty Acids in Samples of Milk Fat for Cows Fed Normal Rations...

Table 7. Saturated Acids as % of Total Acids of Milk Fat ...

Evaporated milk is a Hquid product obtained by the partial removal of water only from milk. It has a minimum milk-fat content of 7.5 mol % and a minimum milk-solids content of 25.0 mol %. Evaporated skimmed milk is a Hquid product obtained by the partial removal of water only from skimmed milk. It has a minimum milk-solids content of 20.0 mol %. Sweetened condensed milk is a product obtained by the partial removal of water only from milk with the addition of sugars. It has a minimum milk-fat content of 8.0 mol % and a minimum milk-solids content of 28.0 mol %. Skimmed sweetened condensed milk is a product obtained by the partial removal of water only from skimmed milk with the addition of sugars. It has a minimum milk-solids content of 24.0 mol %. AH may contain food additives (qv) as stabilizers, in maximum amounts, including sodium, potassium, and calcium salts of hydrochloric acid at 2000 mg/kg singly citric acid, carbonic acid, orthophosphoric acid, and polyphosphoric acid at 3000 mg/kg in combination, expressed as anhydrous substances and in the evaporated milk carrageenin may be added at 150 mg/kg. 

Anhydrous Milk Fat. One high milk-fat material is butter oil (99.7% fat), also called anhydrous milk fat or anhydrous butter oil if less than 0.2% moisture is present. Although the terms are used iaterchangeably, anhydrous butter oil is made from butter and anhydrous milk fat is made from whole milk. For milk and cream there is an emulsion of fat-ia-semm, for butter oil and anhydrous milk fat there is an emulsion of semm-ia-fat, such as with butter. It is easier to remove moisture ia the final stages to make anhydrous milk fat with the semm-ia-fat emulsion. 

Butter. In the United States about 10 wt % of edible fats used are butter. Butter is defined as a product that contains 80% milk fat with not more than 16% moisture. It is made of cream with 25—40% milk fat. The process is primarily a mechanical one in which the cream, an emulsion of fat-in-semm, is changed to butter, an emulsion of semm-in-fat. The process is accompHshed by churning or by a continuous operation with automatic controls. Some physical properties are given in Table 16 (see Emulsions). 

Ice Crea.m, Ice cream is a frozen food dessert prepared from a mixture of dairy iugredients (16—35%), sweeteners (13—20%), stabilizers, emulsifiers, flavoriug, and fmits and nuts (qv). Ice cream has 10—20% milk fat and 8—15% nonfat solids with 38.3% (36—43%) total soHds. These iugredients can be varied, but the dairy ingredient soHds must total 20%. The dairy iugredients are milk or cream, and milk fat suppHed by milk, cream butter, or butter oil, as well as SNF suppHed by condensed whole or nonfat milk or dry milk. The quantities of these products are specified by standards. The milk fat provides the characteristic texture and body iu ice cream. Sweeteners are a blend of cane or beet sugar and com symp soHds. The quantity of these vary depending on the sweetness desired and the cost. 

MeUorine is similar to ice cream except that the milk fat is replaced with vegetable fat (6% min). The total soHds in mellorine are 35—39%, of which there are 10—12% milk soHds. 

Nutritional Value of Milk Products. Milk is considered one of the principal sources of nutrition for humans. Some people are intolerant to one or more components of milk so must avoid the product or consume a treated product. One example is intolerance to lactose in milk. Fluid milk is available in which the lactose has been treated to make it more digestible. The consumption of milk fat, either in fluid milk or in products derived from milk, has decreased markedly in the 1990s. Whole milk sales decreased 12% between 1985 and 1988, whereas the sales of low fat milk increased 165%, and skimmed milk sales increased 48% (35). Nutritionists have recommended that fat consumed provide no more than 30 calories, and that consumption of calories be reduced. Generally, a daily diet of 2000—3000 cal/d is needed depending on many variables, such as gender, type of work, age, body responses, exercise, etc. Further, there is concern about cholesterol [57-88-5] and density of fat consumed. Complete information on the nutritive value of milk and milk products is provided on product labels (36) (see also Table 4). 

The most popular chocolate in the United States is milk chocolate. The U.S. Chocolate Standards state that milk chocolate shall contain no less than 3.66 wt % of milk fat and not less than 12 wt % of milk soHds. In addition, the ratio of nonfat milk soHds to milk fat must not exceed 2.43 1 and the chocolate Hquor content must not be less than 10% by weight. Some typical formulations of milk chocolate and some compositional values are shown in Table 7 (5). 

Lecithin (qv), a natural phosphoHpid possessing both hydrophilic and hydrophobic properties, is the most common emulsifier in the chocolate industry (5). The hydrophilic groups of the lecithin molecules attach themselves to the water, sugar, and cocoa soflds present in chocolate. The hydrophobic groups attach themselves to the cocoa butter and other fats such as milk fat. This reduces both the surface tension, between cocoa butter and the other materials present, and the viscosity. Less cocoa butter is then needed to adjust the final viscosity of the chocolate. 

Control of the polymorphic forms in cocoa butter is further compHcated by the presence of other fats such as milk fat. The fat in a chocolate can be likened to the mortar between the bricks in a mason s wall. The soHd particles in a weU-conched chocolate bed down better than the soHds in a coarsely refined and poorly mixed one (30). 

In milk approximately 90% of the yellow color is because of the presence of -carotene, a fat-soluble carotenoid extracted from feed by cows. Summer milk is more yellow than winter milk because cows grazing on lush green pastures in the spring and summer months consume much higher levels of carotenoids than do cows ham-fed on hay and grain in the fall and winter. Various breeds of cows and even individual animals differ in the efficiency with which they extract -carotene from feed and in the degree to which they convert it into colorless vitamin A. The differences in the color of milk are more obvious in products made from milk fat, since here the yellow color is concentrated. Thus, unless standardized through the addition of colorant, products like butter and cheese show a wide variation in shade and in many cases appear unsatisfactory to the consumer. 

There are no universally accepted definitions of substitute dairy foods, which are referred to as imitations, simulates, substitutes, analogues, and mimics and are associated with terms such as filled, nondairy, vegetable nondairy, and artificial milk, cheese, etc. The term nondairy has been used indiscriminately to describe both imitation dairy products and products legally defined as not being imitation dairy products. Dairy substitutes can be divided into three types those in which an animal or vegetable fat has been substituted for milk fat those that contain a milk component, eg, casein [9000-71-9] or whey protein and those that contain no milk components (see Milk and milkproducts). The first two types make up most of the substitute dairy products. 

The physical characteristics of a fat or oil for imitation dairy products are not necessarily dictated by the fat being replaced, but by the composition, processiag methods, and conditions of use of the substitute product. Thus, the selection of the fat or oil is generally developed experimentally. The chemical and physical nature of the components of the system, order of addition, shear iaput, and processiag temperature dictate the final iateractions and the nature of the product. A comparison of the characteristics of milk fat and three different fats that are used ia satisfactory filled and imitation milks are listed ia Table 1 and those that comprise whipped toppiag, ia Table 2. 

In the United States, ice cream must contain at least 10 percent milk fat, and at most 50 percent air, and must weigh at least... 

Sherbets have a milk-fat content between 1 and 2 percent, and they usually contain more sugar. Often flavored with fruit, a gallon of sherbet weighs a minimum of six pounds. 

Whipping cream is cream that contains at least 30 percent milk fat. Cream that has less than 30 percent fat will not whip. Heavy cream can contain up to 40 percent milk fat, and is sometimes used for whipping. 

The structure of whipped cream is quite complex. A coating of milk protein surrounds small globules of milk fat containing both solid and liquid fats. These globules stack into chains and nets around air bubbles. The air bubbles are also formed from the milk proteins, which create a thin membrane around the air pockets. The three-dimensional network of joined fat globules and protein films stabilizes the foam, keeping the whipped cream stiff. 

Butyric acid in edible fats GC BCR CRM 164, Anhydrous milk fat Ulberth 1998... 

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