Frying Stability of Purified Mid-Oleic Sunflower Oil Triacylglycerols with Added Pure Tocopherols and Tocopherol Mixtures (original) (raw)
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Effect of tocopherols on the frying stability of regular and modified canola oils
Journal of the American Oil Chemists' Society, 2001
A study was conducted to compare the relationship between frying stability and levels and degradation rates of tocopherols in regular and three modified canola oils. Oils were heated at 175 ± 2°C for a total of 72 h, with french fries fried intermittently. Frying stability was compared based on the rates of formation of free fatty acids (FFA) and total polar compounds (TPC). Significant differences (P < 0.05) were identified between oils using analysis of covariance and t-tests for multiple comparisons. No significant differences were observed in the rates of FFA formation among the canola oils during frying. Nevertheless, regular canola (RCO) and high-oleic, low-linolenic acid canola (HOLLCO) oils produced less FFA compared to higholeic (HOCO) and low-linolenic acid (LLCO) canola oils. However, LLCO and HOCO both had significantly (P < 0.05) faster rates of TPC formation compared to HOLLCO or RCO. HOLLCO with the highest level of tocopherols (893 mg/kg) exhibited a slow rate of degradation which accounted for a halflife of 48-60 h of frying. RCO, with a lower level of tocopherols (565 mg/kg), however, had the slowest degradation rate with a half-life of >72 h. In contrast, HOCO and LLCO with 601 and 468 mg/kg tocopherols, respectively, both exhibited a half-life for tocopherols of 3-6 h of frying. An inverse relationship was observed between TPC formation and the reduction of tocopherol. Thus, the greater frying stability of RCO and HOLLCO appears to be affected far more by the rate of tocopherol degradation than by any changes in fatty acid composition.
Enhancing Quality and Oxidative Stability of Aged Fried Food with ?-Tocopherol
J Agr Food Chem, 2003
To determine the effects of γ-tocopherol on the stability of fried food, potato chips were fried in triolein with 0, 100, or 400 ppm γ-tocopherol. Potato chips, sampled at 1, 3, and 6 h of frying time, were aged for 0, 2, and 4 days at 60°C and then evaluated for odor attributes by sensory analysis and for volatile compounds by purge-and-trap gas chromatography-mass spectrometry. Oil sampled after 1, 3, and 6 h of frying time from the fryer was evaluated for total polar compounds and retention of γ-tocopherol. Oil extracted from the potato chips was also analyzed for residual γ-tocopherol. γ-Tocopherol disappeared rapidly, with only slight amounts of the original 100 ppm level detectable after the triolein was used for frying. γ-Tocopherol significantly inhibited polar compound production in the triolein. Results showed that γ-tocopherol inhibited the oxidation of the fried food even when only very low levels of retained γ-tocopherol were present in the frying oil or potato chips. Nonanal formation was inhibited by γ-tocopherol in aged potato chips. Odor analysis of the aged potato chips showed that samples with 0 ppm γ-tocopherol had a rancid odor after being aged for 4 days. Potato chips with 400 ppm γ-tocopherol had no rancid odors; however, as the level of γ-tocopherol decreased in the triolein and in the potato chips, a weak plastic odor characteristic of oxidized triolein was detected.
Journal of the American Oil Chemists' Society, 2003
Formation of undesirable odors and flavors during food processing operations is an important problem for the food industry. To determine the effect of γ-tocopherol on these negative attributes of fried food, we fried potato chips in triolein with 0, 100, or 400 ppm γ-tocopherol. Triolein extracted from potato chips was sampled for residual γ-tocopherol and nonvolatile degradation products after the chips were aged. RP-HPLC coupled to atmospheric pressure chemical ionization MS and sizeexclusion chromatography was used to analyze samples for degradation products in the triolein absorbed in potato chips as well as the fryer triolein. MS results showed that γ-tocopherol reduced the production of nonvolatile degradation products in the triolein absorbed by the potato chips and in the triolein in the fryer. Fryer oil samples and extracted potato chip oils with 400 ppm γ-tocopherol had a significantly lower production of degradation compounds than did samples with 100 ppm γ-tocopherol. Both fryer oils and potato chips containing 100 ppm γ-tocopherol had significantly fewer nonvolatile degradation products than did the samples without γ-tocopherol. These nonvolatile compounds are known precursors of negative odors and flavor compounds produced during the frying and aging of foods.
Analytical Letters, 2020
The decomposition of tocopherol homologs and their influences upon the decomposition of unsaturated fatty acids were explored by studying the reduction in tocopherol homologs and fatty acid contents in 10 commercial edible oils during deep frying at 180 C. The results showed that the decomposition of total tocopherols was faster than for the total unsaturated fatty acid (TUFA). With the decomposition of TUFA, the decomposition rates of tocopherol homologs were in the order c-tocopherol > a-tocopherol > d-tocopherol in 10 oils, regardless of the initial content and composition of tocopherol and fatty acids. It was also found that higher oil unsaturation led to slower tocopherol decomposition during frying, with more tocopherol remaining after the procedure. The result of multiple regression analysis (DTUFA t ¼ 0.049 Da t þ 0.044 Dc t þ 0.052 Dd t þ 0.733) revealed that the effects of tocopherol homologs on the decomposition of unsaturated fatty acid in 10 oils during frying were in the same order, that is, c-tocopherol > a-tocopherol > d-tocopherol.
International Journal of Food Properties, 2015
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Enhancing Quality and Oxidative Stability of Aged Fried Food with γ-Tocopherol
Journal of Agricultural and Food Chemistry, 2003
To determine the effects of γ-tocopherol on the stability of fried food, potato chips were fried in triolein with 0, 100, or 400 ppm γ-tocopherol. Potato chips, sampled at 1, 3, and 6 h of frying time, were aged for 0, 2, and 4 days at 60°C and then evaluated for odor attributes by sensory analysis and for volatile compounds by purge-and-trap gas chromatography-mass spectrometry. Oil sampled after 1, 3, and 6 h of frying time from the fryer was evaluated for total polar compounds and retention of γ-tocopherol. Oil extracted from the potato chips was also analyzed for residual γ-tocopherol. γ-Tocopherol disappeared rapidly, with only slight amounts of the original 100 ppm level detectable after the triolein was used for frying. γ-Tocopherol significantly inhibited polar compound production in the triolein. Results showed that γ-tocopherol inhibited the oxidation of the fried food even when only very low levels of retained γ-tocopherol were present in the frying oil or potato chips. Nonanal formation was inhibited by γ-tocopherol in aged potato chips. Odor analysis of the aged potato chips showed that samples with 0 ppm γ-tocopherol had a rancid odor after being aged for 4 days. Potato chips with 400 ppm γ-tocopherol had no rancid odors; however, as the level of γ-tocopherol decreased in the triolein and in the potato chips, a weak plastic odor characteristic of oxidized triolein was detected.
Food Control, 2011
This paper aims to study discontinuous deep frying of potatoes, milanesas (breaded bovine Semimembranosus muscle) and churros (flour, water, milk, lemon and salt) in soybean oil, sunflower oil and partially hydrogenated fats, monitored by conventional and unconventional methods. With the exception of partially hydrogenated fat after 80.5 h of deep-frying churros, all the oils exceeded 25% of total polar compounds (TPC) and the content of polymeric and dimerized triacylglycerols were higher than 10%, prevailing thermal alterations. For none of the samples the percentage of free fatty acids exceeded 2% of oleic acid. The losses of tocopherols during frying reached 76.0%. Little significant alterations occurred in the fatty acids composition, iodine index calculated, saponification index and formation of trans isomers after frying. The rapid tests used to determine TPC, malondialdehyde and alkenals have proved to be viable alternatives to monitor the quality of frying oils.
2013
Background. Understanding of oil deterioration during heating/frying process is important as oils are normally kept hot at commercial food outlets during intermittent frying cycles. An increased level of consumer awareness toward fat composition and its impact on human health could have an effect on selection of fats in the food industry. The rate of quality deterioration during heating depends on fatty acid composition and also the content and composition of minor components. Therefore, the use of more stable frying oils would be desirable. The present study compares the heat stability at frying temperature of regular sunfl ower oil (RSFO) with that of high-oleic acid sunfl ower oil (HSFO). Material and methods. Heating test was carried out at 185 ±5°C for the samples RSFO and HSFO using electric fryer for 8 h/day for 3 consecutive days. The samples were collected every 4 h. The changes in physicochemical properties of the samples were monitored by analytical and instrumental metho...
Effect of antioxidants on losses of tocopherols during deep-fat frying
Food Chemistry, 1995
The changes in tocopherol content of oil used for deep-fat frying of potatoes have been studied. It has been found that cw-tocopherol is lost much faster than p, */-or 6 tocopherol, with a reduction of 50% cY-tocopherol after 4-5 frying operations compared with values of about 7 and 7-8 frying operations for /3and y-tocopherol, respectively, in the absence of added antioxidants. However, the presence of a rosemary extract or ascorbyl palmitate in the frying oil caused a marked reduction in the rate of loss of the tocopherols.
Molecules
The antioxidant activity of tocopherols in vegetable oils was shown to chiefly depend on the amount and the tocopherol homolog present. However, the most effective ratio of tocopherol homologs with regard to the antioxidant capacity has not been elucidated so far. The present study analyzed the effect of different tocopherol concentrations, homologs and ratios of homologs on markers of lipid oxidation in the most commonly consumed vegetable oils (canola, sunflower, soybean oil) stored in a 12 h light/dark cycle at 22 ± 2 • C for 56 days under retail/household conditions. After 56 days of storage, the α-tocopherol-rich canola and sunflower oil showed the strongest rise in lipid peroxides, yielding 25.1 ± 0.03 meq O 2 /kg (+25.3-fold) and 24.7 ± 0.05 meq O 2 /kg (+25.0-fold), respectively. ESR experiments, excluding effects of the oils' matrices and other minor constituents, confirmed that a food representative tocopherol ratio of (γ + δ)/α = 4.77, as represented in soybean oil, led to a more pronounced delay of lipid oxidation than a lower ratio in canola (1.39) and sunflower oil (0.06). An optimum (γ + δ)/α-tocopherol ratio contributing to the oxidative quality of vegetable oils extending their shelf life has to be investigated.