L.P. Posati

Lipid conversion factors for calculating fatty acid contents of foods

Abstract and SummaryThe U.S. Department of Agriculture is searching the world literature published since 1960 for data on food lipids and their fatty acid composition. These data are being used to update and expand the national tables of food composition and to establish a computerized nutrient data bank. Customarily, investigators report fatty acid data in terms of weight percent of total methyl esters. For the benefit of users of nutrient tables, relative amounts of com-ponent fatty acid esters should be converted to grams fatty acid (as free acid) per 100 grams food. For this purpose, conversion factors, defined as the weight of fatty acids in 1 gram of fat, were derived for various food products. Derivation of, and basis for, factors and their application are described for selected food products. Variables affecting factors are also dis-cussed. Investigators should include, in reports on fatty acid composition of foods, information on total lipid content and on the fatty acid content of the lipid. The latter values are readily obtained by a saponification procedure, complete acid hydrolysis, or if desired, by lipid class analysis.

Changes in thermal and optical properties of butteroil on hydrogenation

The hydrogenation of butteroil was studied at varying conditions of temperature, hydrogen pressure and catalyst concentration. The calculation of reaction rates employing the first order rate equation yielded a single kinetic slope for hydrogenations performed at 60 psi (gauge), whereas a double slope was obtained at 15 psi (gauge). Near infrared spectral data of hydrogenated samples at 4600 cm−1 indicated good quantitative correlation with iodine values. Differential thermal analysis showed progressive disappearance of low-melting groups with concomitant appearance of high-melting groups as the hydrogenation time was progressively increased. Heats of melting, calculated from thermogram areas, showed a systematic increase as the amount of unsaturation was gradually reduced.