Robert J. Peterson

Chemical reactions involved in the deep-fat frying of foods1

Deep-fat frying is one of the most commonly used procedures for the preparation and manufacture of foods in the world. During deep-fat frying, oxidative and thermal decompositions may take place with the formation of volatile and nonvolatile decomposition products, some of which in excessive amounts are harmful to human health. A limited survey of frying fats used in commercial operations indicated that some were maintained at good quality and others were overused or abused. The volatile decomposition products produced by corn oil, hydrogenated cotton-seed oil, trilinolein, and triolein, under simulated commercial frying conditions, were collected, fractionated, and identified. A total of 211 compounds were identified. The nonvolatile decomposition products produced by trilinolein, triolein, and tristearin under simulated commercial frying conditions were collected and characterized. After being treated under deep-fat frying conditions at 185 C for 74 hr, trilinolein yielded 26.3% non-urea-adduct-forming esters, triolein yielded 10.8%, and tristearin also yielded 4.2%.

Chemical reactions involved in the deep-fat frying of foods. VII. Identification of volatile decomposition products of trilinolein1

The acidic and nonacidic volatile decomposition products (VDP) produced by pure trilinolein maintained at 185 C with periodic injection of steam were collected, fractionated, and identified. One hundred thirty-three volatile compounds were positively or tentatively identified. The compounds identified included a number of new and interesting compounds, some with valuable organoleptic properties, such as the unsaturated lactones.

Chemical reactions involved in the deep- fat frying of foods: IX. Identification of the volatile decomposition products of triolein

The acidic and nonacidic volatile decomposition products (VDP) pro-duced by pure triolein maintained at 185 C with periodic injection of steam were collected, fractionated and identified. A total of 93 compounds were positively or tentatively identified. A number of the compounds found were identified for the first time in fats or oil VDP. Among these newly identified compounds are: unsaturated acids, keto-substituted unsaturated acids, ω-enals, unsaturated esters and an unsaturated γ-lactone.

Identification of volatile flavor compounds developed during storage of a deodorized hydrogenated soybean oil

Hydrogenated soybean oil, even after it has been thoroughly deodorized, will develop a characteristic, objectionable flavor known as hydrogenation flavor during storage. The volatile compounds in such an oil were isolated, fractionated by gas chromatography, and the gas chromatographic fractions identified by IR and mass spectrometry. A total of 48 compounds was identified. Among them, 2-trans-6-trans-octadienal, and higher alcohols and lactones, appeared to play an important role in contributing to the hydrogenation flavor.