Effect Of Food Processing

The carotenoids are altered or partly destroyed by acids, usually but not always stable in inorganic bases, can be destroyed by some enzymes (eg, lipoxygenase), and are usually bleached by light. Most carotenoids are fat soluble and thus are not subject to leaching losses. Generally they are fairly stable to the heat involved in canning but are rapidly lost on dehydration because of oxidation.

Although the most stable form of the carotenoids is the all-trans form, the cis-geometrical isomer can form upon heating, especially in the presence of H+. The cis-isomer carotenoids are naturally present in the tangerine tomato. It has been shown that if ^-carotene activity was set at 100%, the neo-/?-carotene vitamin A activity was 38%, and the neo-a-carotene activity was 13%. The transformation from trans to cis results in a loss of extinction and a shift in absorption maxima to shorter (2-5 mm). Cooking causes the formation of cis isomers from all-trans /?-carotene (38). Broccoli lost 13%, spinach lost 7%, and the sweet potato lost 32% of the all-irans isomer. A 15% loss of vitamin A was reported, mainly due to a cis-trans isomerization of a- and ^-carotene during canning. High-temperature short-time (HTST) processing was shown to have less effect on the carotene in the sweet potato than conventional cooking (35).

Heat processing produced enough acid in pineapple to cause the formation of cis isomers. This could result in a lighter yellow color.

The formation of 5,6-and 5,8-epoxides of /^-carotene in model systems has been studied. Diphenylamine, a free-radical inhibitor stopped the loss of ^-carotene. It is generally thought that epoxide formation is the initial step in the degradation of the carotenoid. Several reports have been published that show the complexity of the reactions. Stored hydrogenated oils and enzymatic-coupled oxidation of carotenoids result in the formation of epoxides and other products.

A number of studies have reported an apparent increase in the level of carotenes in various canned products over the fresh product. There are two reasons for this surprising result. Where soluble solids are leached out of the products during cooking and storage, the fat-soluble carotenes appear to increase in amount. It has also been observed that the fresh control may have an active lipoxy-genase-like enzyme that bleaches the carotenoids. When antioxidants were added to the fresh sample before extraction, the vitamin A value in the fresh product increased.

Dehydration and size reduction of fruits and vegetables increase surface area and, if products are not protected from light and oxygen, result in poor stability of the carotenoid pigments. The shelf life of the carotenoids in the dry state is shorter than in the wet state. Different dehydration methods result in varying losses of carotenes. Retention of carotene in fresh carrots varies; fresh carrots retain more than (100%), blanched (95%), freeze-dried (89%), air-dried (80%), and puff-dried (12%). Carotenoid oxidation in foods is generally associated with unsaturated fatty acids and is usually autocatalytic. The oxidation may or may not be enzymatic in nature and is directly related to the available water (Aw), oxygen, heat, and certain metals. Generally antioxidents are effective in slowing the reaction. The decomposition products from a simulated de-oderization of red palm oil were isolated. Beta 151- and /j14'-apo-carotenals and 13 apo-carotenone were isolated from the reaction mixture and a pathway for the reaction was suggested.

Homemade Pet Food Secrets

Homemade Pet Food Secrets

It is a well known fact that homemade food is always a healthier option for pets when compared to the market packed food. The increasing hazards to the health of the pets have made pet owners stick to containment of commercial pet food. The basic fundamentals of health for human beings are applicable for pets also.

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