Effect of oil replenishment during deep‐fat frying of frozen foods in sunflower oil and high‐oleic acid sunflower oil

Abstract

Frying stability of sunflower oil (SO) with 23% oleic acid and 61% linoleic acid, and of high-oleic acid sunflower oil (HOSO) with 74% oleic acid and 13% linoleic acid was studied during 20 discontinuous deep-fat fryings of various frozen foods, with or without frequent replenishment of the used oil with fresh oil. Alterations of both oils were measured by column, gas-liquid and high-performance size-exclusion chromatography. Total polar content and compounds, related to thermoxidative changes, and diacylglycerides, related to hydrolytic changes, increased in all oils during frying but reached higher levels in SO than in HOSO. Nevertheless, the increased levels of diacylglycerides observed may result from the frozen potatoes prefried in palm oil. Oleic acid in HOSO and linoleic acid in SO significantly decreased, but the fatty acid modifications that occurred during the repeated fryings were not only related to thermoxidative alteration but also to interactions between the bath oil and the fat in the fried products. Data from this study also indicated that HOSO performed more satisfactorily than SO in repeated fryings of frozen foods. Moreover, frequent addition of fresh oil throughout the deep-frying process minimized thermoxidative and hydrolytic changes in the frying oils and extended the frying life of the oils. JAOCS 75, 161-167 (1998).

Impact of Frying on Fatty Acid Profile and Rheological Behaviour of Some Vegetable Oils

“…The increase observed throughout the frying in the oleic acid concentration is not easy to explain, but it could be due to the migration of this fatty acid from the food products into the bath oil. A similar hypothesis was suggested by Romero et al [5] to explain the increase in linoleic acid in high-oleic SO used 20 times for frying. The results show that the decrease in C18:2 and the increase in C16:0, C18:0 and C18:1 across two consecutive days of frying was higher in CO than in the SO and PO.…”

“…The non-volatile decompositional products are produced primarily by thermal oxidation and polymerisation of unsaturated fatty acids. These compounds are of concern because they accumulate in the frying oil, promote further degradation, absorbed by the fried food, enter the diet and affect the public health [3][4][5][6]. Therefore, the quality of the frying medium is crucial to the nutritional quality and shelf-life of the final products.…”

Physicochemical characterization of changes in different vegetable oils (olive and sunflower) under several frying conditions Caracterización fisicoquímica de los cambios en diferentes aceites vegetales (oliva y girasol) bajo varias condiciones de fritura

“…The SO showed the highest final amount of trans fatty acids. Trans C18:1 was the most increased trans fatty acid in all oils after 60 frying cycles, being similar to the results reported by Romero et al (1998) in EVOO, HOSO, and SO after 20 frying cycles. The two mono-trans isomers of linoleic acid hardly increased after 60 frying cycles in HOSO.…”

“…However, the increased levels of palmitic acid were more important than the decreased levels of oleic acid (from 71.77% to 67.17% in HOSO and from 75.56% to 69.91% in EVOO) or increased oleic acid (from 33.80% to 36.25% in SO) in reducing the MUFA/SFA ratio. Romero, Cuesta and Sa´nchez-Muniz (1998) and Romero, Sa´nchez-Muniz and Cuesta (2000b) also observed a decrease of linoleic acid and an increase of palmitic and oleic acids in SO after 20 fryings, and Pozo-Diez, Masoud-Musa, Pe´rez-Camino and Dobarganes (1995) also reported a decrease of linoleic and oleic acids, and an increase of palmitic acid in HOSO after 15 fryings. On the contrary, Romero et al (1998) reported an increase of linoleic acid in HOSO.…”

“…Romero, Cuesta and Sa´nchez-Muniz (2000a) and Pozo-Diez et al (1995) reported that frozen pre-fried potatoes fried in SO and HOSO release 55-70% and 80% of fat to the batch fryers, respectively. According to Romero et al (1998), a part of the increased levels of palmitic acid in the saturated fraction of all oils (7.70% in SO,6.83% in HOSO,and 6.25% in EVOO) should come from palm oil often used to make these pre-fried potatoes. Fat extracted from the frozen pre-fried potatoes contained 45.03% of palmitic acid, 4.52% of stearic acid, 39.1% of oleic acid, and 8.71% of linoleic acid.…”