Deep Frying Oil Research Articles

Deep-frying Oil Properties of Diacylglycerol-rich Cooking Oil

Deep-frying oil properties of diacylglycerol-rich cooking oil (DG oil) were examined so as to assess the extent of thermally oxidative deterioration. The results obtained were compared with those for triacylglycerol-rich oil (TG oil). Autoxidation of DG oil at 50°C was much slower compared to TG oil. The viscosity of DG oil exceeded that of TG oil and both these parameters increased with the heating of either oil. Acid value (AV) of fresh DG oil (0.49) was higher than that of TG oil (0.11). AV, carbonyl and p-anisidin values of DG and TG oil increased with the number of uses. It follows from the present findings that the thermal oxidation of DG oil during deep-frying is basically the same as that of TG oil.

低酸素雰囲気におけるフライイングは油脂と食品の酸化的劣化を遅らせる（原標題は英語）

The thermoal oxidation rete of oil at 180°C was previously found proprtional to atmospheric oxygen in contrast to autoxidation of fats and oils at room temperature that could be retarded under an atmosphere containing less than 1% oxygen. Chicken nughetts were deepfried in high-oleic safflower oil and soybean under 2% or 20% oxygen and the quality of the frying oil and flavor of the nughetts were assessed periodically. Based on acid and carbonyl values, content of polar compounds and other parameters, deterioration of deep-frying oil was efficiently retarded by frying under 2% oxygen. When residual tocopherol levels in the frying oil decreased to less than 10mg/100g (high-oleic safflower oil), 60mg/100g (soybean oil), oxidative deterioration was extensive. Foods deep-fried of low oxygen showed significantly better quality at 40h in soybean oil and 10h in high-oleic safflower oil, compared with the control. Lessening oxygen concentration by replacement with nitrogen gas would thus appear to improve the stability of deep-frying oil and of fried food quality.

A new spectrophotometric method for the rapid assessment of deep frying oil quality

AbstractA new and quick spectrophotometric method was developed to assess deep‐frying oil quality. The scanned spectrophotometric curves of the frying oil samples from 350 and 650 nm wavelength changed systematically with the duration of deep frying. The absorbances of the frying oil samples, especially those measured at 490 nm, increased significantly during frying and were significantly correlated to frying time (r ≥0.95, P<0.001). There was a strong correlation between the absorbances of a set of oil samples taken from 0 to 80 h of deep frying and total polar compound contents in the same set of oil samples analyzed using the American Oil Chemists' Society official method (r=0.974, P<0.001). The equation for conversion of the absorbances to total polar compound contents is y=−2.7865x2 +23.782x+1.0309. The absorbances of 10 different types of frying oils with samples taken from 0 to 80 h of deep frying in duplicate were also strongly correlated to total polar compounds in the same oil samples (r=0.953, P<0.001, n=220). The results show that this method is fast, simple, convenient, and reliable.

Color and Chemical Properties of Deep Frying Oil from Household Kitchens

Color and Chemical Properties of Deep Frying Oil from Household Kitchens

Effect of deep frying oil given with and without dietary cholesterol on lipid metabolism in rats

The purpose of the present study was to investigate the effect of dietary deep frying oil (DO) on levels of plasma and liver lipids, and fecal steroid excretion in rats. The DO was prepared by frying fresh soybean oil (FO) at 200°C, 6 h each, for four consecutive days. Male weanling Sprague-Dawley rats ingested diets containing 15% FO or DO with or without 1% cholesterol for 6 weeks. Rats on the DO diet with cholesterol had a lower food intake and body weight gain compared to the FO diet with cholesterol. The concentration of plasma esterified cholesterol was higher in rats on DO diet than in rats on FO diet, although the plasma triacylglycerols (TG) were similar between the groups. The DO diet resulted in a lower content of liver TG and cholesterol, and less excretion of acidic and neutral steroids than did the FO diet. These results showed that ingestion of frying oil with cholesterol aggravated hypercholesterolemia, even though absorption of dietary cholesterol may be lower in rats on DO diet.