Summer milk

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. 

The concentration of vitamin A and carotenoids in milk is strongly influenced by the carotenoid content of the feed. Milk from animals fed on pasture contains higher levels of carotenes than that from animals fed on concentrate feeds. There is also a large seasonal variation in vitamin A concentration summer milk contains an average of 62 fig retinol and 31 fig carotene per 100 g while the values for winter milk are 41 and 11 fig per... 

In cow s milk, nearly all of the vitamin E is a-tocopherol and the level can vary with the cow s feed and the season of the year (Lampert 1975). For example, summer milk can contain five times more vitamin E (1.1 mg a-tocopherol per quart) than winter milk (0.2 mg/quart) (Hertig and Drury 1969 McLaughlin and Weihrauch 1979). It is suggested that vitamin E, due to its antioxidant properties, may have some effect in retarding the development of oxidized flavor in milk (Lampert 1975). 

The principal factor that influences the a-tocopherol content of milk is the feed of the cow, as influenced by the season of the year. Kanno et al. (1968) reported that summer milk produced on green pasture feed averaged 33.8 pg a-tocopherol/g fat, while winter milk produced on dry-lot feeding averaged 21.6 pg a-tocopherol/g fat. Similar findings have been reported by King et al. (1967) and Seerless and Armstrong (1970). 

COW (milk from Jersey and Guernsey cows contains more riboflavin than Holstein milk). Summer milk generally contains slighly higher levels of riboflavin than winter milk. Interspecies variations in concentration are also apparent. Raw sheep s milk contains about 0.32 mg per 100 g while the mean value for pasteurized goats milk (0.13 mg per 100 g) is lower human milk contains 0.03 mg per 100 g. Dairy products also contain significant amounts... 

The seasonal variation in milk fat composition is demonstrated in Table 3.153, winter milk fat being more saturated than summer milk fat. The trans fatty acid content is not frequently recorded. Literature values vary between 2 and 11% with higher values in the summer. The determined values are very method-dependent and values in the range 4-8% are probably realistic (Deman and Deman, 1983). The main trans monounsaturated acid is tran -vaccenic acid (18 1 n-1) (Hay and Morrison, 1970 Lund and Jensen, 1983). 

To optimize this crystallization and finally obtain an oil/fat ratio optimal for the churning process, a defined temperature regime must be applied (see below). This regime depends strongly on the composition of the milk fat, which is subject to seasonal variations the iodine value of winter milk fat is about 30 and that of summer milk fat about 40. 

The D vitamins are limited in distribution. They rarely occur in plants except in sun-dried roughages and the dead leaves of growing plants. In the animal kingdom vitamin D3 occurs in small amoimts in certain tissues and is abundant only in some fishes. Halibut-liver and cod-Uver oils are rich somces of vitamin D3. Egg yolk is also a good source, but cow s milk is normally a poor somce, although summer milk tends to be richer than winter milk. Colostrum usually contains six to ten times the amoimt present in ordinary milk. 

Russian Spring- Summer Encephalitis 1, Aerosol 2. Milk None High 8-14 days Days to months Moderate Relatively unstable Yes Not effective Yes... 

It is not certain that the presence of CLA in tissue lipids is due entirely to the production of cis-9, trans-11 as an intermediate during the biohydrogenation of linoleic acid in the rumen. However, the amount of CLA in milk (7 J) and butter (14) is positively correlated to the level of dietary linoleic acid. Some long chain fatty acid intermediates reach the small intestine and are normally absorbed and deposited into adipose tissue (75). There is seasonal variation in CLA content of milk, with the highest values occurring usually in summer (76). 

Seasonal Variation and the Influence of Temperature. In temperate latitudes, rather characteristic seasonal variations in milk composition are commonly observed. Both fat and solids-not-fat contents are lower in summer than in winter. In the survey by Overman (1945) of individual cows at the University of Illinois, monthly extremes for fat were 4.24 and 3.81% in January and August and for protein were 3.61 and 3.37% in January and July, respectively. Nickerson (1960) found significant seasonal differences in 18 components of bulk milks from six areas in California. Seasonal differences in fat and protein contents were similar to those observed in Illinois. Seasonal variations in milk composition could conceivably be caused by differences in temper-... 

Deman and Deman (1983) have investigated the determination of trans unsaturation in milk fat by infrared analysis and found values of 7.4% (winter) to 9.9%(summer) when the TGs were analyzed. These are higher than the quantities found by infrared analysis of methyl esters of the fatty acids. These quantities are isolated total trans bonds and do not give an estimate of the positional and polyunsaturated isomers which are present. The trans contents obtained by Deman and Deman are higher than the 4% found by Smith et al. (1978). 

Both copper and iron are normal components of milk. Murty et al. (1972) studied the trace mineral content of market milk from various regions of the United States for one year and found that the levels of copper and iron were highest in winter and lowest in summer. Disregarding variations due to individuality, stage of lactation, and contam-... 

As vitamin A and carotene are in the fat portion of milk, the vitamin A activity is removed with the milk fat during separation into cream and lowfat and skim milks. Consequently, standards of identity established by the U.S. Food and Drug Administration (FDA) mandate the addition of vitamin A (e.g., retinyl palmitate) to fluid lowfat and skim milks and to nonfat dry milk to a level approximating that found in whole milk from cows on summer pasture. That is, at least 2000 IU of vitamin A must be present in each quart of lowfat and skim milk (FDA... 

Milk contains some important vitamins. The vitamin D content niav vary from. 10 I.U. per quart in summer to 6 in winter, depending upon the Iced and the sunlight which reach the cow. Both pasteurized and evaporated milk are often fortified by the addition, on a fluid basis, of 400 I.U. of vitamin D per quart. Vitamins A. D, and F. (alpha-tocopherol) are fal-soluble and stable at the heat treatments used in processing milk and milk products. The remaining stlamlns arc water-soluble and of varying stability Vitamins B,... 

Concerning the fresh Asiago, the electronic nose and the GC-MS data were well correlated, recognizing same samples as outliers in particular, the samples 1 and 25 of the winter period resulted to be cheeses lacking substances typical of the fresh milk having unpleasant lactic fermentation aromas. Samples 3 and 6 of the summer period were a little fermented and more sweet, particularly sample 6 was remarked by the Committee of the Consortium for the aroma of cooked. 

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