J.C. Alexander

Biological effects due to changes in fats during heating

In deep-fat frying the fat is used over and over again, and moisture and air are mixed into the hot oil. Substantial quantities of the heated fat are absorbed into the fried foods. Many reports from experimental observations with animals fed these fats have shown biological effects ranging from a slight depression in growth, all the way to very poor growth, diminished feed efficiency, increased liver size, fatty necrosis of the liver, and various other organ lesions. Obviously, certain fat constituents may be changed by frying conditions, and the adverse biological effects are relative. We are at the stage in studying these heated fats where selected techniques including biochemical parameters, histopathological evaluations, and tissue culture in monolayers can be good indicators of some of the specific effects on biological tissues. Isolated fractions from heated fat samples, which contained concentrations of cyclic monomer and dimer derivatives, were used in animal studies. Incorporation of the above materials into rat diets produced distended flatulent stomachs and intestines, gastric ulcers, and multiple focal hemorrhages. Histological evaluation of heart, liver, and kidney tissue sections indicated extensive cellular damage. Livers and kidneys exhibited the most severe lesions. Neonatal heart cells established as monolayers on glass cover slips were exposed to fractions from heated or fresh fats. Cellular damage including pyknosis, vacuolization of the cytoplasm, and mitotic aberrations were observed. Uptake of14C-labeled fatty acid by the triglyceride fraction of the cells was increased with heated fats.

Stability of edible oils and fats to fluorescent light irradiation

Butter, butterfat, and corn, coconut, rapeseed, and soybean oils were exposed to 500 ft-c of fluorescent light at varying time-temperature conditions. Oxidation rates were measured by the peroxide values. Vitamin A and β-carotene content of butterfat were estimated. The effect of wavelength on the relative rates of oxidation was determined. The light transmitting properties of the samples at 15 and 30 C over a spectral range of 380–750 nm were measured. It was observed that there was no increase in oxidation rate when the light was switched off. The stability of the oils as shown by the oxidation rates did not correlate well with the ratios of C18:2 to C18:1 or C18:3 to C18:2 nor with the degree of unsaturation. Increase in temperature alone had minimal effect; however, in the presence of light the rate of oxidation increased considerably with a corresponding decrease in the content of Vitamin A and β-carotene. β-Carotene provided strong protective properties. After the photobleaching of β-carotene in butterfat, there was a rapid increase in peroxide values. With coconut oil, the oxidation rate was greater at 15 C than at 30 C due to greater light absorption at 15 C over the entire spectrum. The rate of oxidation decreased at higher wavelengths, and this effect was more pronounced in the vegetable oils than in butterfat, where the β-carotene was considered to serve as a filter for light of low wavelength.

The Value of Microwave Radiations in the Processing of Full-Fat Soybeans

Abstract The value of processing unextracted soybeans by microwave radiations has been investigated. The optimum heating period required to produce beans of good nutritive quality, as judged chemically by the cre-sol red dye absorption test, was determined and found to be in the range of 2 to 3 minutes. The effect of microwave heating on the fatty acid content of soybeans was examined using gas liquid chromatography and it revealed that processing for periods of up to 6 minutes resulted in no destruction of the fatty acids. Beans produced under the selected microwave conditions were compared with beans processed by conventional heating techniques for their ability to support rat growth. It was shown that microwave processing can yield beans of high nutritive value, which compared favourably to beans processed by conventional heating techniques.