Milk, irradiation

Irradiation. Although no irradiation systems for pasteurization have been approved by the U.S. Food and Dmg Administration, milk can be pasteurized or sterilized by P tays produced by an electron accelerator or y-rays produced by cobalt-60. Bacteria and enzymes in milk are more resistant to irradiation than higher life forms. For pasteurization, 5000—7500 Gy (500,000—750,000 tad) are requited, and for inactivating enzymes at least 20,000 Gy (2,000,000 rad). Much lower radiation, about 70 Gy (7000 tad), causes an off-flavor. A combination of heat treatment and irradiation may prove to be the most acceptable approach. 

Burton, H. (1951). Ultraviolet irradiation of milk. Dairy Sci. Abstr. 13, 229-244. 

Sagan, C. E. and Lengemann, F. W. (1973). The retention and movement of cerium-141 in the gastrointestinal tract of adult rats irradiated with 800 R and fed grain-based or milk diets, Radiat. Res. 53,480. 

Voillequ , P. G. and Pelletier, C. A. (1974). Comparison of external irradiation and consumption of cows milk as critical pathways for 137Cs, MMn and 144Ce-144Pr released to the atmosphere, Health Phys. 27, 189. 

Vitamin Dj, UV-irradiated ergocalcHerol from yeast is added to milk and other dairy products.)... 

Methoxychlor-DDE and p,p-dimethoxybenzophenone were formed when methoxychlor in water was irradiated by UV light (Paris and Lewis, 1973). Compounds reported from the photolysis of methoxychlor in aqueous, alcoholic solutions were p,p-dimethoxybenzophenone, p-methoxybenzoic acid, and 4-methoxyphenol (Wolfe et al., 1976). However, when methoxychlor in milk was irradiated by UV light (A. = 220 and 330 nm), 4-methoxyphenol, methoxychlor-DDE, p,p-dimethoxybenzophenone, and l,l,4,4-tetrakis(p-methoxyphenyl)-l,2,3-butatriene were formed (Li and Bradley, 1969). 

A relatively new method uses 172 or 222 nm excimer radiation in nitrogen atmosphere.i The irradiation causes a surface cure of the acrylate coating similar to milk skim in appearance. In the second step, the coating is fully cured by UV or EB. 

Whole cows milk contains 0.4-1.8 fig vitamin K per 100 g while human milk contains about 0.2 fig per 100 g. Human colostrum contains higher concentrations of vitamin K, which are necessary since bacteria capable of synthesizing vitamin K take time to become established in the intestine of the neonate. Irradiation under anerobic and apolar conditions can result in cis-trans isomerization, resulting in loss of activity since only the trans isomer has vitamin K activity. However, unit operations in dairy processing are unlikely to have an effect on the stability of this nutrient. 

Inhibition by Light and Ionizing Irradiation. The milk lipoprotein... 

Irradiation by ionizing radiation and its effect on milk lipase activity have also been studied (Tsugo and Hayashi 1962). Irradiation doses of 6.6 x 104 rads destroyed 70% of the activity. The udders of lactating cows, when exposed to 60 Co gamma rays, gave milk with decreased lipase and esterase activity (Luick and Mazrimas 1966). 

Day, E. A., Forss, D. A. and Patton, S. 1957. Flavor and odor defects of gamma-irradiated skim milk. I. Preliminary observations and the role of volatile carbonyl compounds. J. Dairy Sci. 40, 922-931. 

Khatri, L. L. 1966. Flavor chemistry of irradiated milk fat. Diss. Abst. 26, 6638-6639. 

Tsugo, T. and Hayashi, T. 1962. The effect of irradiation by ionizing radiation on milk enzymes. III. Effect of irradiation on lipase and xanthine-oxydase activities in milk. Jap. J. Zootech. Sci. 33, 125-129. 

Li, W., Murai, Y., Okada, E., Matsui, K., Hayashi S., Horie, M., and Takano, Y. (2002) Modified and simplified western blotting protocol use of intermittent microwave irradiation (IMWI) and 5% skim milk to improve binding specificity. Pathol. Int. 52, 234-238. 

One of the first cases of the application of membrane bioreactors in food processes was the production of milk with low lactose content. (3-galactosidase was entrapped into cellulose acetate fibers to carry out the hydrolysis of milk and whey lactose [2] recently the system was improved by the use of microfiltration and by UV irradiation of the enzyme solution to avoid growth of micro-organisms [45]. 

Yeast and hen s egg for ergos-terol animal products for 7-dehydrocho-lesterol irradiated ergos-terol for vitamin D2 fish liver oil, milk, egg yolk, irradiated 7-dehy-drocholes-terol for vitamin D,. 

The precursors of vitamins D2 and D3 are ergosterol and 7-dehydrocholesterol, respectively. These precursors or provitamins can be converted into the respective D vitamins by irradiation with ultraviolet light. In addition to the two major provitamins, there are several other sterols that can acquire vitamin D activity when irradiated. The provitamins can be converted to vitamin D in the human skin by exposure to sunlight. Because very few foods are good sources of vitamin D, humans have a greater likelihood of vitamin D deficiency than of any other vitamin deficiency. Enrichment of some foods with vitamin D has significantly helped to eradicate rickets, which is a vitamin D deficiency disease. Margarine and milk are the foods commonly used as carrier for added vitamin D. 

The vitamin D potency of milk can be increased in several ways by feeding cows substances that are high in vitamin D activity, such as irradiated yeast by irradiating milk and by adding vitamin D concentrates. The latter method is now the only commonly used procedure. The practice of irradiating milk to increase the vitamin D potency has been discontinued, undoubtedly because of the deteriorative action of the radiation on other milk components. Vitamin D is added to milk to provide a concentration of 400 IU... 

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