Milk fat and other animal fats

Fats of animal origin were the first to be used for edible purposes. Although in recent years the volume of these fats produced has stayed approximately constant (or increased only slightly), the demand for them for edible purposes has in most cases decreased—due at least in part to perceived or potential health problems. This is because all fats of animal origin contain cholesterol as the major sterol, a constituent that is normally considered to be of negative value in the diet and because, with the exception of most marine fats, they are high in saturated fatty acids, which is also seen as a negative attribute. 

Animal fats fall naturally into three main groups marine, milk and carcass fats. 

Animal fats are the only group of fats where their absence, or the absence of one type (pork), can be a desirable attribute, as opposed to the more normal 

The necessity for non-consumption of fat from a particular source is usually religious, most commonly from Jews and Moslems. The religious laws forbid the consumption and use of pork products. There are also requirements concerning shellfish, but shellfish oil is not, and would be unlikely to ever be, a commercial product. 

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Chapter 5 describes milk and other animal fats. Expensive bovine milk fats have often been adulterated in the past and, with the increased marketing of milk products from other species, this is an area requiring investigation. One might think that carcass animal fats are not likely to be adulterated, as they are often cheaper than vegetable alternatives. While this is a reasonable initial assumption, there is a considerable market for foods and products... 

Vitamin E is widespread in foods and is stored in the body so that deficiency states are very rare. A possible exception may be premature infants with very low fat stores. The concentration of a-tocopherol in cows milk ranges from 3.0 to 5.0 mg/L and is present at about the same level in human milk. While vitamin E has been shown to be essential for normal fertility in rats and other animals, it has never been proven to be necessary for human fertility. However, in recent years there has been renewed interest in the antioxidant function of vitamin E [e.g., in protecting the cardiovascular system (Sytkowski et al., 1990 Gurr, 1994)]. 

Milk consists of 85—89% water and 11—15% total soflds (Table 1) the latter comprises soflds-not-fat (SNF) and fat. Milk having a higher fat content also has higher SNF, with an increase of 0.4% SNF for each 1% fat increase. The principal components of SNF are protein, lactose, and minerals (ash). The fat content and other constituents of the milk vary with the animal species, and the composition of milk varies with feed, stage of lactation, health of the animal, location of withdrawal from the udder, and seasonal and environmental conditions. The nonfat soflds, fat soflds, and moisture relationships are well estabhshed and can be used as a basis for detecting adulteration with water (qv). Physical properties of milk are given in Table 2. 

When DDT is fed to animals, even in small quantities, there is an accumulation of the compound in the tissues, particularly the fat. Telford and Guthrie (18), Orr and Mott (13), Woodward et al. (20, 21), and Laug and Fitzhugh (9) have demonstrated that DDT will accumulate in certain tissues and in milk fat of domestic and laboratory animals. Marsden and Bird (12) found that DDT was toxic to turkeys in concentrations above 0.075% of the diet, and that turkeys fed the insecticide for 7 to 8 weeks stored DDT in their fat at concentrations ranging from 4 to 8 times that in the diet. Rubin et al. (14) reported that hens fed 0.062% DDT in their diet for 12 weeks showed reduced egg production with lowered hatchability. At one half this concentration there was a detrimental effect on egg production, but hatchability was not seriously affected. The hens were killed by doses of 0.125% DDT. The insecticide was found in the eggs in quantities much smaller than in the body fat. Harris et al. (8) have shown that DDT will accumulate in considerable quantities in the fat of lambs fed DDT-treated hay. Small amounts of the insecticide were found in other tissues. 

Hopkins was late in realizing that one of his accessory food substances, later called vitamins, was contained in the fat of milk as well as in the fats of other animals and in certain plant tissues as well. (17, 18) Osborne and Mendel actually reached a point in their research in 1912 that made them confident that fats as fats were not necessary at all in the diets of experimental rats. (19) McCollum went so far as to state at one time that aside from the anti-scorbutic substance (later to be known as vitamin C), there were only two new substances to be concerned... 

Even though liquid whey has been successfully commercialized in the form of alcoholic and nonalcoholic beverages, these are still a rarity in most countries. Most whey is converted to whey solids as ingredients for human food or animal feeds by traditional processes such as spray drying, roller drying, concentration to semisolid feed blocks, or production of sweetened condensed whey. Jelen (1979) reported other traditionally established processes including lactose crystallization from untreated or modified whey, production of heat-denatured whey protein concentrate, or recovery of milk fat from whey cheese in whey butter. ... 

The fat-soluble vitamins comprise vitamins A, D, E, and K, whose biological activities are attributed to a number of structurally related compounds known as vitamers. Also included are those carotenoids that are precursors of vitamin A. Recommended dietary allowances (RDAs) based on human epidemiological and experimental animal studies have been published in the United States for vitamins A, D, E, and K (1). Other countries and international bodies have compiled similar recommendations. In the United States and Canada, fluid milk is supplemented by law with vitamin D to a level of 400 international units per quart (10 /zg/0.95 L) to meet the RDA of 10 p%. Other commodities, such as margarine, milk products, ready-to-eat breakfast cereals, and dietetic foods, are commonly supplemented with vitamins A, D, and E. Except for infant formulas, vitamin K is not added to foods. The addition of vitamins to a particular processed food is intended to provide a specific proportion of the RDA. 

Other food samples like egg, animal fat and fish oil appear to behave very similarly to milk fat and extensive validation has not been carried out thus far. The suitability was, however, demonstrated by inclusion of positive or spiked samples. The assay was validated for blood samples from wildlife species for high concentrations of dioxins and dioxin-like PCBs.13 A special clean-up procedure was developed and validated for sediment, pore water and other environmental samples, allowing the use of the assay for official testing of these type of samples.14... 

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