QUALITY CHANGES OF REFINED-BLEACHED-DEODORIZED (RBD) PALM OLEIN, SOYBEAN OIL AND THEIR BLENDS DURING DEEP-FAT FRYING

The quality changes of refined, bleached and deodorized palm olein (RBDPO) and soybean oil (SBO) and their blends were investigated in this study. The oils were studied during intermittent frying of potato chips at 180PT5C for 5 h per day for 5 consecutive days. The indices used for assessment of changes in quality of the oils were fatty acid composition (FAC), peroxide value (PV), anisidine value (AnV), % free fatty acid (FFA), iodine value (IV), % polar component, polymer content, color, viscosity, smoke point and foaming tendency. The results showed that RBDPO was superior to SBO in frying performance in terms of resistance to oxidation, changes in IV, AnV, foaming tendency, % polar component and polymer content. However, SBO performed better than RBDPO with respect to color, viscosity, FAA content and smoke point. Sensory evaluation showed that potato chips fried in both RBDPO and SBO were equally acceptable by the panelists.     

COMPARISON OF THE FRYING PERFORMANCE OF REFINED, BLEACHED AND DEODORIZED PALM OLEIN AND COCONUT OIL

The frying performance of refined, bleached and deodorized palm olein (RBDPO) and refined, bleached and deodorized coconut oil (RBDCO) was compared in this study. The oils were studied during intermittent frying of potato chips at 180C for 5 h/day for 5 consecutive days. The indices used for assessment of frying performance of the oils were fatty acid composition (FAC), peroxide value (PV), anisidine value (AnV), % free fatty acid (FFA), iodine value (IV), % polar component, polymer content, color, viscosity, smoke point and foaming tendency. The results showed that RBDPO was superior to RBDCO in frying performance in terms of % FFA, iodine value, foaming tendency and smoke point. However, RBDCO performed better than RBDPO with respect to % polar component, polymer content, resistance to oxidation, color and viscosity. Flavor evaluation showed that potato chips fried in RBDPO were preferred by the panelists.     

稻米油调和油煎炸应用研究

通过与棕榈油对比180℃下炸制薯片以及评估薯片感官喜好度、质构、口感及粘牙性等差异来评价稻米油调和油的煎炸应用性能。结果表明:采用稻米油调和油煎炸的薯片中多不饱和脂肪酸含量显著高于棕榈油(P<0.05),且其薯片的整体感官喜好度、质构口感、酥脆度、粘牙喜好度,均显著优于棕榈油薯片(P<0.05)。在加速氧化条件下,采用稻米油调和油炸制的薯片的酸价、过氧化值均与棕榈油炸制的薯片无显著性差异(P>0.05),且远低于GB 16565-2003的规定。在加速存储过程中,谷维素却得到了很好的保留。总之,稻米油调和油具有良好的煎炸性能。     

Quality changes of edible oils during vacuum and atmospheric frying of potato chips

Demand for safe and nutritionally rich fried products is gaining a momentum among consumers, leading to the increased consumption of vacuum fried products. The impact of vacuum frying (VF)(110 °C, 40 kPa) on chemical composition of food, fatty acid profile, microstructure, oxidative stability and sensory attributes was assessed and differentiated with that of atmospheric frying(AF) (180 °C). The potato slices were fried in mustard and soyabean oil used repetitively for 25 h. The oil content of VF potato chips was lower (15.18%) than AF chips (18.98%), however water loss in AF chips was higher than VF chips by 1.63-fold. VF significantly prevented the PUFA degradation, minimizes transfatty acid (TFA) formation and maintain a low C18:2/C16:0 ratio as compared to AF. VF Chips fried in soyabean oil show an increase in TFA content from 2.15 to 2.63% and a decrease in PUFA from 51.57 to 45.16% as compared to AF chips where TFA content increased from 2.15 to 3.72% and PUFA shows a higher reduction from 51.57 to 37.69% at the end of 25 h of frying. This indicate that in AF, oil is safe for use upto 10 cycles of frying, while as in VF, the same oil can be used for upto 40 cycles of frying without quality deteoriation. Sensorial analysis revealed that VF chips retain a better colour, taste and flavour but were less crispy than that of AF chips. These findings validate the application of vacuum frying technology for the production of high-quality foods with lesser degradation of frying oil.Industrial relevanceFood manufacturers are now impelled by the health-conscious consumer base for the production of healthy food products. The toxic effect of foods fried in degraded oils on human health is now widely known and thus the production of safe fried foods is the need of hour globally. In this context, vacuum frying is the most feasible approach for the production of quality fried products retaining the natural colour, flavour, sensory and nutritional properties better than that of atmospheric frying. Vacuum frying causes the least degradation of fatty acid of the frying oil and the fried potatoes, producing healthy potato chips. Therefore, the oil used for vacuum frying have a greater shelf life and oxidative stability than atmospheric frying. However, the higher installation cost of vacuum fryer still limits its use in the street fried food market, where degradation of oil is more likely. Thus, for its widespread commercialisation in developing countries, steps should be taken both by government and manufacturing companies to reduce the installation costs.     

High-Temperature Natural Antioxidant Improves Soy Oil for Frying

ABSTRACT:  The objectives of this study were to determine the frying stability of soybean oil (SBO) treated with a natural citric acid-based antioxidant, EPT-OILShield™ able to withstand high temperatures and to establish the oxidative stability of food fried in the treated oil. Soybean oil with 0.05% and 0.5% EPT-OILShield and an untreated control SBO were used for intermittent batch frying of tortilla chips at 180 °C for up to 65 h. Oil frying stability was measured by free fatty acids (FFA) and total polar compounds (TPC). Chips were aged for up to 4 mo at 25 °C and evaluated for rancid flavor by a 15-member, trained, experienced analytical sensory panel and for hexanal content as an indicator of oxidation. Oil with 0.05% EPT-OILShield had significantly less FFA and TPC than the control. The effect of EPT-OILShield was apparently retained in aged chips because hexanal levels were significantly lower in chips fried in oil with 0.05% EPT-OILShield than in chips fried in the control. Tortilla chips fried in the control were rancid after 2 mo at 25 °C at sampling times evaluated from 25 to 65 h; however, chips fried in oil with 0.05% EPT-OILShield and used for 65 h were described as only slightly rancid after 4 mo. Gamma tocopherol levels were significantly higher in the chips fried in the oil with 0.05% EPT-OILShield than in the control, helping to inhibit oxidation in the tortilla chips during storage.     

ASCORBYL PALMITATE AS AN ANTIOXIDANT FOR DEEP FAT FRYING OF POTATO CHIPS IN PEANUT OIL

The antioxidative properties of ascorbyl palmitate (AP) alone and in combination with other known antioxidants were investigated during deep fat frying of potato chips in peanut oil. Their effect on the quality of the frying oil and shelf-life of the fried product were studied. The other antioxidants tested were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl gallate (PG). The characteristics evaluated for the frying oil were color development, viscosity, peroxide value (PV) and polymerization of the oil during deep fat frying; AP was found to reduce these values. It also helped to prevent the degradation of the oil by retaining the unaltered triacylglycerols during the frying period. Addition of AP to the frying oil reduced the PV of the extracted fat, doubled the shelf-life of the fried product and improved the quality of frying oil with increase in frying time. However, AP did not show any synergistic effect with other antioxidants examined.     

Use of natural antioxidants in refined palm olein during repeated deep-fat frying

An optimization study on the use of oleoresin rosemary extract, sage extract and citric acid added into refined, bleached and deodorized (RBD) palm olein before deep-fat frying of potato chips was performed using a constrained mixture design. Results revealed that the use of these natural antioxidants could improve the sensory acceptability of potato chips during a 5-day repeated deep-fat frying. All three antioxidants significantly (P<0.05) improved the sensory characteristics, including appearance, taste, crispiness, odor and overall acceptability. After day 5 of frying, the most acceptable fried potato chips were those fried in oil containing a combination of 0.059% oleoresin rosemary extract, 0.063% sage extract and 0.028% citric acid. The natural antioxidants significantly (P<0.05) lowered the rate of oxidation of oil during deep-fat frying and contributed to measured sensory acceptability of fried potato chips.     

Vacuum frying of high-quality fruit and vegetable-based snacks

Sweet potato, green beans, Tommy Atkins mango, and blue potato were fried in a vacuum frying process at a temperature of 120-130 ± 1°C. Before frying, green beans and mango slices were soaked in a 50% maltodextrine 0.15% citric acid solution. The products were also fried in a traditional (atmospheric pressure) fryer at 160-165 ± 1°C for 4 min. A 30-member consumer panel rated the sensory quality of both types of fried snacks using a 1-9 hedonic scale. Compared with traditional frying, oil content of vacuum-fried sweet-potato chips and green beans was 24% and 16% lower, respectively. Blue potato and mango chips had 6% and 5% more oil, respectively, than the traditional-fried samples. Anthocyanin (mg/100 g d.b.) of vacuum-fried blue potato chips was 60% higher. Final total carotenoids (mg/g d.b.) were higher by 18% for green beans, 19% for mango chips, and by 51% for sweet-potato chips. Sensory panelists overwhelmingly preferred (p < 0.05) the vacuum-fried products for color, texture, taste, and overall quality. Most of the products retained or accentuated their original colors when fried under vacuum. The traditional-fried products showed excessive darkening and scorching. These results support the applicability of vacuum frying technology to provide high-quality fruit and vegetable snacks.     

Effect of frying oil quality and TBHQ on the shelf-life of potato crisps

Three different systems were used for the evaluation of the effect of frying oil quality and tertiarybutyl hydroquinone (TBHQ) on the shelf-life of fried potato crisps. Batches of potato slices were fried for 4 min at 30 min intervals over a period of 5 h day^?1 for eight consecutive days in refined, bleached and deodorised palm olein (RBD olein) without antioxidant (system 1); RBD containing 200 μg g^?1 TBHQ at the start of the experiment (system 2) and RBD olein which had TBHQ topped up to a level of 200 μg g^?1 at the start of each frying day (system 3). Sensory evaluation of crisps showed that there is an initial rapid decrease in shelf-life with increase in fry number in all systems. There was only a comparatively smaller effect on shelf-life with increase in fry number in later fryings. When the shelf-life of crisps was related to the quality of oil in the frying medium, it was found that the shelf-life of the product is only slightly affected when the oil had deteriorated beyond the acceptable limit of quality of frying oil, where the acceptable limit was taken as 27-30% polar components and 1–2 mg potassium hydroxide g^?1 oil. TBHQ does have a protective carry-through effect. The protective effect is more pronounced when TBHQ is topped up to a level of 200 μg g^?1 at the beginning of each frying day.     

Potato Chip Quality and Frying Oil Stability of High Oleic Acid Soybean Oil

High oleic soybean (HOSBO) and low linolenic acid soybean (LLSBO) oils were evaluated individually and in a 1:1 blend along with cottonseed oil (CSO) to determine frying oil stabilities and the flavor quality and stability of potato chips. Potato chips were fried in the oils for a total of 25 h. Potato chips and oils were sampled periodically for sensory data, gas chromatographic volatile compounds, free fatty acids, and total polar compounds. Total polar compounds levels decreased with increasing amounts of oleic acid. The LLSBO had the highest overall increase (17.3%) in total polar compounds from 0 to 25 h of frying. Flavor evaluations of fresh and aged (0, 1, 3, 5, and 7 wk at 25 °C) potato chips showed differences between potato chips fried in different oil types. Potato chips fried in either LLSBO or in the 1:1 blend had significantly higher intensities of deep fried flavor than the chips fried in HOSBO. Potato chips fried in HOSBO, which had 2% linolenic acid and 1.3% linoleic acid, had significantly higher fishy flavor intensity than chips fried in the other oils. The presence of linoleic acid at a level lower than the amount of linolenic acid probably allowed for the fishy flavors from the degradation of linolenic acid in HOSBO to become more apparent than if the linoleic acid level was higher than linolenic acid. Hexanal was significantly higher in potato chips fried in LLSBO than in the chips fried in the other oils, indicating low oxidative stability during storage. Blending HOSBO with LLSBO in a 1:1 ratio not only improved flavor quality of chips compared with those fried in HOSBO, but also improved oil fry life and oxidative stability of chips compared with LLSBO.     

Changes in oil and potato chips during frying

The effect of frying of potato chips (batch processing during 12 h) on the chemical characteristics and fatty acid composition of the used oil were determined. Samples of the fried oil and potato chips were taken at various time periods. The volatile carbonyl compounds of the aroma concentrate of each sample were isolated and their oxime derevatives were prepared and subsequently estimated by UV absorption for the total oximes and conjugated diene carbonyl oximes. The development of the volatile carbonyl compounds in both frying oil and fried potato chips was increased on continued frying. Concerning the frying oil this increase was found to be in coincident with the decrease in the linoleic and linolenic acid percent.     

Vacuum frying as a route to produce novel snacks with desired quality attributes according to new health trends

Consumers look for products that contribute to their wellness and health, however, even health-conscious consumers are not willing to sacrifice organoleptic properties, and intense full-flavor snacks remain an important trend. The objective of this study was to examine most important quality parameters of vacuum (1.92 inHg) and atmospheric-fried carrot, potato, and apple slices to determine specific advantages of vacuum technology. Slices were fried using equivalent thermal driving forces, maintaining a constant difference between oil temperature and the boiling point of water at the working pressure (ΔT = 60 and 80 °C). This resulted in frying temperatures of 160 and 180 °C, and 98 and 118 °C, for atmospheric and vacuum frying, respectively. Vacuum-fried carrot and potato chips absorbed about 50% less oil than atmospheric-fried chips, whereas vacuum-fried apple chips reduced oil absorption by 25%. Total carotenoids and ascorbic acid (AA) were greatly preserved during vacuum frying. Carrot chips vacuum fried at 98 °C retained about 90% of total carotenoids, whereas potato and apple slices vacuum fried at 98 °C, preserved around 95% of their initial AA content. Interestingly, results showed that the antioxidant capacity of chips may be related to both the presence of natural antioxidants and brown pigments developed at elevated temperatures. PRACTICAL APPLICATION: A way to reduce detrimental effects of deep-fat frying is through operating-pressure reduction, the essence behind vacuum deep-fat frying. In this way, it is possible to remove product moisture at a low temperature in a low-oxygen environment. The objective of this research was to study the effect of oil temperature reduction when vacuum frying traditional (potatoes) and nontraditional products (carrots and apples) on most important quality attributes (vitamins, color, and oil uptake). Results are promising and show that vacuum frying can be an alternative to produce nutritious and novel snacks with desired quality attributes, since vitamins and color were greatly preserved and oil absorption could be substantially reduced.     

EVALUATION OF THE TEXTURE OF FRIED POTATOES

Texture of potatoes with different shapes (slices and strips) were evaluated after frying and in some cases after baking. Blanched and unblanched potato slices (Bintje variety) were fried at four oil temperatures: 160, 170, 180 and 190C until reaching a moisture content of ∼1.7%. A puncture test with three point support for the slices was applied to measure the texture of potato chips using the following parameters extracted from the force versus distance curves: maximum force of break (MFB) and deformation of break (DB). These two parameters were useful to follow the changes in texture of the fried slices with moisture content at different frying temperatures. Blanched and unblanched potato strips were partially fried at 160C and 190C for 60, 90 and 120 s. The par-fried potatoes were frozen at -20C for one day after which they were baked at 200C for 15 min. The texture of the baked potato strips was evaluated using a bending test with two support points. From the force versus distance curves, two parameters were extracted: maximum force of deformation (MFD) and maximum deformation (MD). Significant higher MFB and lower DB values (P > 0.1) for unblanched fried slices indicate that these are crispier than blanched chips for moisture contents lower than 4% (6.59 N and 0.62 mm vs 5.74 N and vs 0.75 mm for unblanched and blanched chips, respectively, average values for the four frying temperatures employed). There was no effect of the frying temperature and the pretreatment (blanching or unblanching) on the texture of the frozen par-fried potatoes after baking when compared at the same residual moisture content, but blanched potato strips lost moisture more slowly both in frying and in baking.     

栀子果油煎炸过程中的品质变化及对油条和薯条的感官影响

为了探究栀子果油煎炸过程中的品质变化,本文选择薯条和油条两种代表性煎炸食材,将栀子果油在煎炸20h内每隔2h的酸价、羰基价、过氧化值和极性组分与大豆油、棕榈油在同等条件下煎炸的理化指标进行比较,结果表明：棕榈油煎炸后的品质较高,栀子果油和大豆油比较相似,栀子果油可以作为煎炸油。但栀子果油连续煎炸12 h时极性组分超过国家现有煎炸油的卫生标准,因此其连续煎炸时间不能超过12 h。同时对1、10、20h煎炸出来的油条和薯条进行感官评价,结果表明：煎炸食材相同时,三种食用油的感官评分无显著性差异（P>0.05）,说明栀子果油对油条和薯条的品质无不良影响,适合作为煎炸油。     

EVALUATION OF OLEIC SAFFLOWER OIL IN FRYING OF POTATO CHIPS

SUMMARY– A recently introduced variety of safflower, UC-1, produces an oil in which oleic:linoleic acid ratios of ordinary safflower oil are reversed, giving an oil with iodine value 90. This oil was compared with cottonseed oil and hydrogenated vegetable oil (HVD) for frying potato chips. After accelerated storage at ambient temperature under fluorescent light, the quality of chips fried in oleic safflower oil was ranked equal to that of chips fried in hydrogenated oil, Chips fried in either oil were more stable than those fried in cottonseed oil. Effect of propyl gallate antioxidant was negligible.     

STUDIES ON DEEP FAT FRYING USING BLENDED OILS AND POTATO CHIPS

Dehydrated potato chips were fried in pure coconut and groundnut oils and their blends in order to study the pattern of uptake of oil constituents during frying. Investigations on the analysis of the oil and fatty acid composition in the fried product and the oil remaining in the frying pan suggested a preferential uptake of saturated lipid constituents by the potato chips, while the oil remaining in the frying pan was rich in unsaturated constituents. This effect was accentuated in blended oils, although it was also observed in pure oils.     

低温真空油炸薯片生产工艺及其贮藏条件的研究

对马铃薯片进行低温真空油炸生产工艺的基础性研究,分析薯片在贮藏过程中水分、脂肪和VC含量的变化,并探讨等温吸湿规律。通过单因素试验确定最优的油炸工艺参数为温度105℃,时间20min,真空度0.090MPa;离心脱油的最佳条件为脱油转速400～500r/min,时间5～7min,真空度0.090MPa。研究结果对低温真空油炸薯片技术具有很好的指导和促进作用,同时改善了现在油炸薯片的品质和提高了能源利用率。     

Oil uptake and texture development in fried potato slices

The objective of this work was to study oil absorption and the kinetics of texture development of fried potato slices during frying. Prior to frying, potato slices were blanched in hot water at 85 °C for 3.5 min. Unblanched slices were used as the control. Control and blanched potato slices (Panda variety, diameter: 37 mm, width: 2.2 mm) were fried at 120, 150 and 180 °C until reaching moisture contents of 1.8% (total basis) and their texture and oil content were measured periodically. Oil uptake was higher in 15% for blanched samples than for control samples after 20 s of frying. Besides, the higher the frying temperature, the lower the oil absorption in control samples. Textural changes in fried potato slices were followed by the parameter maximum force (MF) extracted from the force vs. distance curves corresponding to different sampling times. Normalized maximum force (MF*) was used in modeling textural changes in the potato slices during frying in both the initial tissue softening process and the later crust development process. Higher temperatures accelerated these processes; however neither the temperature nor the pre-treatment had a significant effect (P > 0.05) over the final texture of the fried potato chips.     

Safety evaluation of individual non‐fried and fried sunflower oil,paraffin oil,jojoba oil and their binary mixtures on rat health

Sunflower, jojoba, paraffin oils and binary oil mixtures of sunflower, jojoba and sunflower–paraffin oils were continuously heated at 180 °C for 12 h. Aliquots of potato chips were fried in the aforementioned oil samples. Organoleptic tests were performed on fried chips and safety limits of the oil samples were measured by certain biochemical tests. Histopathological examinations of rat liver and kidney tissues were microscopically done. Organoleptic results for fried potato chips indicate that all types of chips obtained from heated oils were categorised good. Histopathological examinations indicate changes in rat tissues of liver and kidney paralleled the biochemical data. In general, the results suggest that paraffin oil alone and in mixtures with sunflower oil have to ban its use in frying processes.     

大豆油煎炸过程理化指标与煎炸时间相关性研究

针对食用植物油煎炸过程中理化指标是否可有效反映煎炸油品品质变化这一问题,以大豆油为煎炸油,薯条和鸡排为煎炸物质进行煎炸实验。随煎炸时间延长取不同程度煎炸油检测,研究酸值、羰基值、极性组分、p-茴香胺值、过氧化值和总氧化值等理化指标与煎炸时间相关性。结果表明:所研究理化指标中酸值、羰基值和极性组分3项指标与煎炸时间相关性较好,可有效反映油品变坏程度,p-茴香胺值、过氧化值和总氧化值相关性较差。