Underutilised palm stearin as hard stock for deep-frying medium and its performance for oil uptake in instant noodles.

BACKGROUND: As a by-product of the palm oil industry, palm stearin is often overlooked despite having several beneficial properties, such as excellent stability, which is critically essential to meet the demand of the global food trend in producing safer processed food. Specifically, deep frying of food is often associated with the production of toxic compounds that could potentially migrate into the food system when oils are degraded under continuous heating. The incorporation of palm stearin is regarded as a cost-effective and efficient method to modify the fatty acid composition of oils, enhance the frying qualities and lower the degradation rate. RESULTS: This study blended 5% and 10% palm stearin into palm oil to investigate the deep-frying performance and impact on food quality. Increasing the palm stearin content improved the frying oil's oxidative and hydrolytic stability, evidenced by reduction of total polar material, free fatty acid and total oxidation value. Addition of palm stearin increased the slip melting point which improved the oil's oxidative stability but no significant increase in oil content of instant noodles was observed. Scanning electron microscopy and fluorescence microscopy showed the formation of larger pores in the noodle structure that facilitated oil retention. CONCLUSION: Blending palm stearin into frying oil enhanced the frying stability and minimally affected the oil uptake in instant noodles. This article presents the viability of blending palm stearin into frying oils to develop longer-lasting frying oils. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Utilization of molecular distillation for determining the effects of some minor compounds on the quality and frying stability of olive pomace oil.

The objective of this study was to determine the effects of some minor components such as squalene and mono- and diglycerides (MDG) on the frying stability of olive pomace oil. Refined olive pomace oil was distilled using a falling film type short-path distillation unit at 230 °C under a pressure of 0.02 mbar to remove minor components. Distilled olive pomace oil was introduced with approximately 10,000 mg/kg of squalene and 2.5% of MDG. Fryings were performed 8 times/day at 180 °C for 3 min. Whole frying procedure proceeded for 5 days. Total polar compounds, polymerized triglycerides (PTG), free fatty acids, viscosity, color index, p-anisidine value, smoke point, fatty acid composition and iodine values of the oils were monitored. Results indicated that all criteria except smoke point and iodine value increased in all fractions during fryings. The lowest total polar compound was obtained in distilled olive pomace oil while PTG was the lowest in the MDG added fraction. Lower increases in viscosity and color indexes were recorded in squalene incorporated samples. It was observed that squalene and MDG were not effective on the oxidation rate of unsaturated fatty acids during frying.

Performance of antioxidative compounds under frying conditions: A review.

Although much study has been done assessing activity of antioxidants at ambient and accelerated storage temperatures, the results cannot correctly depict their performance under frying conditions. Due to the stringent conditions imposed, most conventional antioxidative compounds failed under frying conditions, suggesting the need for a continuous modification to improve their effectiveness. Although syntheses and performance evaluation of over a hundred (semi)synthetic antioxidants have been reported in literature, only a small fraction have been specifically designed and/or evaluated under frying conditions. Here, the performance under frying conditions of major natural and synthetic antioxidants is reviewed. The recent trend in the designing of antioxidants for frying applications is also reviewed with the view of stimulating further study in this direction.

Effects of deep-fat frying process on the oil quality during French fries preparation.

The performance of the sunflower oil in deep-fat frying was assessed by evaluating the efficacy of linoleic acid level and composition of tocopherol isomeric on its frying stability. The oil was used as a frying media to fry potato strips for 6 h daily for 7 days. Standard procedures for the measurement of used frying oil degradation such as fatty acid composition, acid value, anisidine value, conjugated diene value, total polar compounds and tocopherol concentration were used. At analogous composition of tocopherol isomers, the high oleic sunflower oil with smaller value of linoleic acid content indicated higher frying stability than the oil with higher linoleic acid level. This, indicating that the high oleic sunflower oil frying efficiency was depended mainly with the oil linoleic acid content and the composition of tocopherol isomers showed no significant effect. Also, the α-tocopherol degradation was lower compared to the corresponding degradation of γ-tocopherol.

Performance of Regular and Modified Canola and Soybean Oils in Rotational Frying.

Canola and soybean oils both regular and with modified fatty acid compositions by genetic modifications and hydrogenation were compared for frying performance. The frying was conducted at 185 ± 5 °C for up to 12 days where French fries, battered chicken and fish sticks were fried in succession. Modified canola oils, with reduced levels of linolenic acid, accumulated significantly lower amounts of polar components compared to the other tested oils. Canola oils generally displayed lower amounts of oligomers in their polar fraction. Higher rates of free fatty acids formation were observed for the hydrogenated oils compared to the other oils, with canola frying shortening showing the highest amount at the end of the frying period. The half-life of tocopherols for both regular and modified soybean oils was 1-2 days compared to 6 days observed for high-oleic low-linolenic canola oil. The highest anisidine values were observed for soybean oil with the maximum reached on the 10th day of frying. Canola and soybean frying shortenings exhibited a faster rate of color formation at any of the frying times. The high-oleic low-linolenic canola oil exhibited the greatest frying stability as assessed by polar components, oligomers and non-volatile carbonyl components formation. Moreover, food fried in the high-oleic low-linolenic canola oil obtained the best scores in the sensory acceptance assessment.

Improvement in Frying Stability of Safflower Oil by Blending with Refined Olive Pomace Oil during Deep Fat Frying.

The objective of the present study was to increase the frying stability of refined safflower oil (RSO) by blending it with refined olive pomace oil (ROPO) during deep fat frying. For this purpose; RSO, ROPO and their blends were utilized for frying of potato sticks at 180°C for 3 consecutive days. The frying stability of the oils was monitored by analyzing them for their free fatty acids, peroxide values, total polar contents, ultraviolet spectrophotometric indices at 232 and 270 nm, fatty acid profiles, p-anisidine values, α-tocopherol contents and photometric color indices. 3-monochloropropane-1,2-diol (3-MCPD) and glycidyl ester (GE) levels of oils before and after frying were measured as well. The results have shown that thermooxidative degradation products increased as the frying progressed for all oils, however the decomposition rate was found to slow down in blend oils by stabilizing with ROPO. Blending RSO with ROPO decreased linoleic and linolenic; but increased the oleic and palmitic acid percentages of the blends. C18:2/C16:0 ratio was found to decrease by frying for RSO and the blend oils, however ROPO was not affected significantly. 3-MCPD-E levels of the blends increased as the ratio of ROPO increased. Principal component analysis enabled a clear discrimination between oils with different composition throughout the frying process.

The Frying Stability of Oleogel Made from Rice Bran Wax and Sunflower Oil During Intermittent Frying of Potato Chips.

There is a need for an alternative method of producing a vegetable oil with high levels of unsaturated fatty acids and physical properties similar to solid fat. The objective of current work was to cut down the amount of oil absorbed by the finished product, increase the frying stability of sunflower oil, and fry potato chips using oleogel without harming their sensory quality. Rice bran wax was applied in this experiment, at rates of 2, 4, and 6 weight percent, and the generated oleogels were then utilized for four days in a succession to fry potato chips for four hours each day. The results suggested that potato chips could be fried using the sunflower oil-rice bran wax oleogel without having an adverse effect on their texture, color, or quality. Furthermore, the produced oleogel was more robust during frying than liquid sunflower oil. During intermittent frying, SFA levels also marginally rose in all samples with the exception of 4% oleogel. The control sample, which was sunflower oil, had the lowest levels of unsaturated fatty acids and poly unsaturated fatty acids at the end of the frying operation. The percentage of oil uptake by the potato chips in the oleogels containing 4 and 2% rice bran wax, on the other hand, was lower than in the control sample. The findings suggested that oleogels could be used as a deep-fat frying medium in household, commercial, and industrial settings.

Performance of structured lipids incorporating selected phenolic and ascorbic acids.

Conditions applied during frying require antioxidant which is stable at these conditions and provides protection for frying oil and fried food. Novel structured lipids containing nutraceuticals and antioxidants were formed by enzymatic transesterification, exploring canola oil and naturally occurring antioxidants such as ascorbic and selected phenolic acids as substrates. Lipozyme RM IM lipase from Rhizomucor miehei was used as biocatalyst. Frying performance and oxidative stability of the final transesterification products were evaluated. The novel lipids showed significantly improved frying performance compared to canola oil. Oxidative stability assessment of the structured lipids showed significant improvement in resistance to oxidative deterioration compared to original canola oil. Interestingly, the presence of ascorbic acid in an acylglycerol structure protected α-tocopherol against thermal degradation, which was not observed for the phenolic acids. Developed structured lipids containing nutraceuticals and antioxidants may directly affect nutritional properties of lipids also offering nutraceutical ingredients for food formulation.

Phosphatidylcholine and dihydrocaffeic acid amide mixture enhanced the thermo-oxidative stability of canola oil.

Recently, we reported the synthesis of a series of dihydrocaffeic acid amides and evaluated their performance as antioxidants for frying applications using a model frying. In the present study, the possibility of a synergy between the amide, N-propyl-N-benzyl-3-(3,4 dihydroxyphenyl)propanamide (DCA) and phosphatidylcholine (PC) was explored in a 6-day actual frying operation. As measured by the amount of polar components (TPC), anisidine value (AnV), changes in fatty acid composition, residual tocopherol and hydroxynonenal (HNE), canola oil containing the formulated antioxidant was twice as stable compared to the regular unfortified oil. At the end of the frying period, the amount of HNE detected in regular canola oil and the fortified sample was at 5.7 and 2.5µg/g, respectively. Thus, the mixture containing phosphatidylcholine and dihydrocaffeic acid amide is a promising antioxidant for frying application.

Frying stability of high oleic sunflower oils as affected by composition of tocopherol isomers and linoleic acid content.

The influence of linoleic acid content and tocopherol isomeric composition on the frying performance of high oleic sunflower oil was evaluated during a 14-day restaurant style frying operation. At equal linoleic acid content, no significant difference was observed between high oleic sunflower oil containing only α-tocopherol and the sample containing a mixture of α-, γ-, and δ-isomers as measured by the amount of total polar components, oligomers, anisidine value, and free fatty acids. On the contrary, at similar tocopherol isomeric composition, high oleic sunflower oil containing lower amount of linoleic acid showed superior frying stability compared to the sample with a higher content of linoleic acid, suggesting that the frying performance of high oleic sunflower oil is dictated primarily by the level of linoleic acid, with the tocopherol isomeric composition of the oil having no significant influence. In all oil samples, the loss of γ-tocopherol was higher than the corresponding loss of α-tocopherol.