Pan‐heating of low‐linolenic acid and partially hydrogenated soybean oils

Abstract

Genetically modified low-linolenic acid soybean oil (LL-SBO) was compared to partially hydrogenated soybean oil (PH-SBO). Samples were heated on a Teflon pan at ~180°C until a selected end point of ≥20% polymer content was reached. High-performance size-exclusion chromatography analysis indicated the PH-SBO contained >20% polymer after 20 min of heating, whereas the LL-SBO sample contained >20% polymer after 10 min. Supercritical fluid chromatography analysis indicated degradation rates of 0.161 ± 0.011 min −1 for LL-SBO and 0.086 ± 0.004 min −1 for PH-SBO. The volatile compounds were identified and quantitated with static headspace-GC-MS. 1-Heptene (239.9 ppm) and hexanal (1486.1 ppm) were present at the greatest concentration among the volatile compounds in LL-SBO. The volatile compounds present in the greatest concentrations in heated PH-SBO were hexanal (376.9 ppm) and pentane (82.1 ppm). After 10 min of heating, the LL-SBO oil FFA value (2.66%), p-anisidine value (386.5 abs/g oil), Food Oil Sensor reading (18.75), and color intensity (Y = 4.0, R = 1.0) were significantly greater than those of PH-SBO after 14 min of heating (4.28%, 298.5 abs/g oil, 16.08, Y = 1.0, R = 0.1, respectively). There was a significant difference in the degradation rates between LL-SBO and PH-SBO (P < 0.05). The PH-SBO was more stable than the LL-SBO.Genetic improvements in vegetable oils will continue to play an important role in the development of new frying oils. In 1997, an estimated 23 million acres of genetically modified oilseeds were planted in North America (1). The topic of genetically improved oils has become an area of intense research because most consumers prefer to avoid the saturated and trans FA found in hydrogenated oils. In one set of genetically engineered oils, the FA components have been altered to provide high-stability oil without hydrogenation (2). The frying performance of genetically modified oils has been investigated to determine the effect of changing the FA composition on oil stability and odor intensity. A deep-fat frying study of soybean and canola oils, modified by hydrogenation and/or mutation breeding, indicated a reduction in odor intensity for low-linolenic acid oil (3).Billek (4) investigated the effect of different frying methods on polar-material formation. Ten minutes of pan-frying was comparable to approximately 20 h of deep-fat frying, because these are the heating times required to reach approximately the same percentage of polar materials.Many investigators have published work on deep-fat frying, but very few have studied oil deterioration during pan-frying (5), even though pan-and grill-frying are convenient and common cooking methods used in households and restaurants for preparation of meat, eggs, and vegetables (6). Stir-frying, a form of pan-frying, is a common practice in Chinese cooking. In a study of volatile compounds found during stir-frying, oil was heated at ~200°C in a Chinese wok for 3 min with constant stirring (7). In another study, a thin film of trilinolein was applied t...

The effect of pan frying on thermooxidative stability of refined rapeseed oil and professional blend

“…In this case, the professional blend (PB) is degraded to a lesser degree than RO. Our results are in agreement with other authors, who also report a linear increase in AV content with frying time in different frying media using different methods of frying (Matthäus 2006;Kiatsrichart et al 2003;Soheili et al 2002a;Choo et al 2007). Kiatsrichart et al (2003) stated that during pan-frying using mid-oleic sunflower oil (NuSunoil) and a commercial rapeseed oil more sensitive for hydrolysis was rapeseed oil, however both oils exhibited low level of free fatty acids.…”

“…At the end of frying AnV of rapeseed oil was 184 while of professional blend almost 3-times lower -65. A rapid increase in AnV was observed by other authors (Choo et al 2007;Soheili et al 2002a). The ratio of AnV increase depended on kind of oil as well as on frying procedure.…”

“…Choo et al (2007) observed the highest AnV increase for flaxseed cold-pressed oils used for short pan-frying, when after several minutes (3 and 6 min) AnV increased from 0.4-0.7 to 290-588 and 622-876, respectively. In another study by Soheili et al (2002a), after 10 min of heating at 150°C, the AnVof low-linolenic soybean oil was significantly greater (386.5 abs/g oil) than that of partially hydrogenated soybean oil after 14 min of heating (298.5 abs/g oil). On the other hand during deep-frying process oxidative changes in frying oils were not so intensive (Houhoula et al 2002).…”

“…Kiatsrichart et al (2003) stated that during pan-frying using mid-oleic sunflower oil (NuSunoil) and a commercial rapeseed oil more sensitive for hydrolysis was rapeseed oil, however both oils exhibited low level of free fatty acids. In another experiment Soheili et al (2002a) found that after 10 min of heating the low linolenic soybean oil, free fatty acid content, was lower than in partially hydrogenated soybean oil after 14 min of heating (respectively 2.66 and 4.28 %).…”

The emission patterns of volatile organic compounds during aerobic biotreatment of municipal solid waste using continuous and intermittent aeration

“…Xenobiotic VOCs, which include alkanes, aromatic hydrocarbons, and halogenides, are not produced by biodegradation and are usually inherent in household wastes such as plastic packaging, waste cooking oil, and pesticides on fruits and vegetables (Hodgson et al, 2000;Komilis et al, 2004;Sohelili et al, 2002). Xenobiotic VOCs can be volatized from MSW and usually persist in the exhausted air during the aerobic biological process (Scaglia et al, 2011).…”