Effects of Microwave Energy on the Tocopherols of Soybean Seeds

Abstract

The effects of microwave heating on the tocopherols of soybeans were studied in relation to chemical changes in the lipids. The amounts of cy-, p-, y-, and &tocopherols in the soybeans before microwave treatment ranged from 6.2 to 13.0, 2.7 to 4.5, 60.0 to 76.8, and 45.7 to 57.9 mg/lOO g lipid, respectively. y-and 6-Tocopherol concentrations gradually decreased, and as much as 40% of the tocopherols originally present in the soybeans was lost after 12 min heating. However, microwave treatment of soybeans for 6 min, which would be optimal to prepare full-fat soyflour without a burnt odor, retained ca. 90% of the individual tocopherols with a few exceptions and caused no significant difference in the chemical changes of the lipids.

Proximate composition and vitamin E levels in egg yolk: losses by cooking in a microwave oven

“…The US National Academy of Science, which uses international units (IU) for its recommended daily amounts, recommends the daily consumption of 5 IU for vitamin E. 31 Sometimes the RDA of vitamin E is expressed as 10 mg per day of a-tocopherol equivalents. 66 The antioxidant activity of tocopherols varies with different fractions 60 which explain why the results are expressed in a form which has a more direct application in nutrition.…”

“…60 Heating or cooking by microwaves, which has increased in importance in recent years, involves high levels of energy in order to reduce conventional cooking times. However, the technique oxidises lipids, especially unsaturated fatty acids, to form conjugates and polymers within minutes since microwaves cause the molecules to vibrate strongly, affecting especially the hydrogen atoms of the active methylene groups which are adjacent to the unsaturated centres.…”

Influence of different harvest dates and ripening periods on fruit quality and oil characteristics of Fuerte avocados

“…, 1980) Oil properties: the extracted oil was analyzed for acid value as mg KOH/g, peroxide value as meq /kg and iodine value as g/100g of oil were determined as described in (A.O.A.C., 1990). Color index was determined according to (Yoshida and Kajimoto, 1989), while refractive index determination at 40 0 C was assessed according to (Mordret, et. al., 1985) Determination of fatty acid by GLC: The avocado oil samples were converted to their fatty acid methyl esters by transesterification using 5% hydrogen chloride in dry methanol (Chrisite, 1973).…”

Vitamin E and Oxidative Stability of Soya Bean Oil Prepared with Beans at Various Moisture Contents Roasted in a Microwave Oven

“…The tocopherols were monitored with a fluorescence spectrophotometer (Shimadzu RF-535, Shimadzu Instruments Inc, Kyoto, Japan) set at excitation wavelength 295 nm and emission wavelength 320 nm, quantitated by comparison with peak areas of internal standard (2,3,5,7,8-pentamethyl-6-hydroxy chroman, Eisai Co, Tokyo, Japan). The other HPLC conditions were as reported previously (Yoshida and Kajimoto 1989).…”