Cyclic fatty acid monomers were analyzed by gas chromatography in commercial frying oils, obtained in this country and in the Middle East. Samples were obtained from food outlets in California and Illinois after varying periods of usage. The samples from Egypt and Israel were collected from street vendors frying vegetable patties (known as “fallafel”) in open‐air stands. The United States samples ranged from 0.1 to 0.5% cyclic monomers, and from 1 to 8% polar +noneluted thermal oxidation materials. The Middle Eastern samples showed significantly more heat abuse, with values for cyclic monomers from 0.2 to 0.7% and polar materials ranging from 2 to 22%.
An arachidonic acid 15-lipoxygenase activity was discovered in the gill tissue of teleost fishes during purification of the previously recognized and more preponderant 12-lipoxygenase enzyme. The total activity of this enzyme following purification using hydroxylapatite was significantly greater than in the crude tissue preparation, suggesting that an inhibition was removed during purification. The enzyme was active toward polyunsaturated fatty acids present in the tissue producing hydroxylated metabolites from fatty acids with 18-, 20-, and 22-carbon chain lengths at carbons 13,15, and 17, respectively. The enzyme was further purified by using a Superóse gel filtration column and eluted with an apparent molecular weight of 70 000.
SUMMARY Ethyl trans:2‐cis:4‐decadienoate was identified as a flavor component of Bartlett pear. The acid moiety was synthesized and found to be identical with that isolated from Bartlett pear. Quantities of this acid sufficient for sensory evaluations have been isolated from the seed oil of Sapium sebiferum. This latter source has been used to synthesize a series of esters whose odors are remarkably pear‐like.
Forty‐one brands of nine different types of snack and convenience foods were purchased from food stores and fast service restaurants in the Sacramento area of California. All samples had been prepared by deep‐fat frying. They included potato chips, corn chips, tortilla chips, cheese chips, cheese puffs, cake donuts, french fries, chicken pieces and fish pieces. These samples were analyzed in duplicate for total fat and fatty acid composition. The total lipid content of each type of food varied among different commercial sources; the average percentages were as follows: potato chips, 40; cheese puffs, 38; corn chips, 35; cheese chips, 25; tortilla chips, 24; cake donuts, 22; chicken thighs, 14; french fried potatoes, 14, and fish pieces, 10. The fatty acid profiles of the total lipids in several brands of potato chips were relatively constant. The fatty acid profiles of the total lipids in the corn and cheese snack foods varied widely. Fatty acid compositions of donuts, chicken and fish pieces and french fries were influenced by the amount and fatty acid profile of the lipids in each uncooked food, as well as by the composition of the cooking fat.
This study evaluated some of the changes that occur in shortenings used for commercial deep‐fat frying in fast‐service restaurants. Foods cooked in partially hydrogenated soybean oil were battered chicken parts and french fries. Sixty‐five samples of fresh and used shortenings were collected from nine restaurants on three occasions over a three‐month period. Frying periods varied from 0 to 300 hr, and most samples were taken just before the used fat was discarded. For fresh shortenings, percentages of polar materials, free fatty acids (FFA), materials not eluted by gas chromatography, and fatty acid profiles differed only slightly. For used samples, there were marked variations in these analyses and in increases of dielectric constant measurements. Frying times were highly correlated with increases in dielectric constant, polar materials and FFA. The greatest change in fatty acid profiles occurred intrans‐C18 monoenes which decreased from over 40% to as low as 13%. Due to lipid exchange with chicken fat, both oleic and linoleic acids increased in the shortenings with hours of use, whereas stearic acid decreased. There were high correlations, among increases in dielectric constant, percentages of polar materials and FFA, demonstrating that each of these methods could predict degradation of the shortening. However, the increase in dielectric constant, as measured by a Foodoil Sensor (FOS), was the most convenient for quality control in restaurant situations. In most cases, used shortening was discarded before 100 hr of frying time; and only a few of these samples had FOS readings near 4.0, FFA over 1.00%, or percentages of polar materials over 27%. These values have been suggested as discard criteria. However, a number of samples used between 100 and 300 hr exceeded these limits. There is a need to specify suitable limits, related to quality and health factors, to determine at what point a cooking fat should be discarded.
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