Anti-Rancidity Effects of Sesame and Rice Bran Oils on Canola Oil During Deep Frying

In this study, the effect of sesame oil (SEO) and rice bran oil (RBO) on the rancidity of canola oil (CAO) during the process of frying potato pieces at 180 °C was investigated. The SEO and RBO were added to the CAO at levels of 3 and 6%. Frying stability of the oil samples during the frying process was measured on the basis of total polar compounds (TPC) content, conjugated diene value (CDV), acid value (AV), and carbonyl value (CV). In general, frying stability of the CAO significantly (P < 0.05) improved in the presence of the SEO and RBO. The positive effect of the SEO on the stability of the CAO was more than that of the RBO. Increasing the amounts of SEO and RBO from 3 to 6% led to decreases in the TPC and AV, and increases in the CDV and CV of the CAO during the frying process. The best frying performance for the CAO was obtained by use of 3% of both SEO and RBO together (CAO/SEO/RBO, 94:3:3 w/w/w).     

Phytostanol Supplementation Through Frying Dough in Enriched Canola Oil

The objectives of this study were to determine a suitable level of phytostanols for addition to canola oil and to investigate the performance of the supplemented oil during frying. The frying oil was supplemented with 5, 10, 15, 20 % w/w phytostanols and two suitable levels (5 and 10 %) were selected. Dough frying was performed for 5 consecutive days at 180 °C for 5 h/day. The ranges of analytical measurements in the treatment groups were; free acidity (0.12–10.07 %), conjugated dienes (0.47–1.37 %), total polar material with probe (9.00–51.25 %), viscosity (46.27–195.51 cP), turbidity (0.82–1.80 NTU), and smoke point (202.75–274.25 °C). The results indicated that 5 % phytostanol enriched oil was superior in terms of oil stability and sensory quality of the fried dough among all the enriched oils. Samples with 10 % added phytostanols were high in free acidity, conjugated dienes and smoke points. Sterol composition analysis showed that the fried dough absorbed total sterols of 49.9 and 95 g/kg in 5 and 10 % supplemented oils, respectively. Hence, some health benefits could be achieved through consuming products which have been fried in phytostanol supplemented canola oil.     

Frying Stability of Canola Oil Blended with Palm Olein, Olive, and Corn Oils

The fatty acid composition, peroxide value (PV), acid value (AV), iodine value (IV), total tocopherols (TT) content, and total phenolics (TP) content of canola oil (CAO), palm olein oil (POO), olive oil (OLO), corn oil (COO), and the binary and ternary blends of the CAO with the POO, OLO, and COO were determined. The blends were prepared in the volume ratios of 75:25 (CAO/POO, CAO/OLO, CAO/COO) and 75:15:10 (CAO/POO/OLO, CAO/POO/COO). The CAO and its blends were used to fry potato pieces (7.0 × 0.5 × 0.3 cm) at 180 °C. During the frying process, the total polar compounds (TPC) content, AV, oil/oxidative stability index (OSI), and color index (CI) of the CAO/blends were measured. In general, frying stability of the CAO was significantly (P < 0.05) improved by the blending, and the frying performance of the ternary blends was found to be better than that of the binary blends.     

Frying Performance of No-<Emphasis Type="Italic">trans</Emphasis>, Low-Linolenic Acid Soybean Oils

Two extruded-expelled physically refined soybean oils with reduced contents of linolenic acid, ultra-low- linolenic acid (ULL, 1.5%) and low-linolenic acid (LL, 2.6%), and a extruded-expelled physically refined control oil (control, 5.3% linolenic acid) were evaluated by frying French fries in a commercial-like setting for 6 h day⁻¹ during 23 days. The oils became darker, increased in yellow color at the beginning, and became redder and less green throughout the process. Free fatty acids levels were not different among the oils until day 14, after which, ULL was different from the control for the remainder of frying. The conjugated dienoic acid values were greatest in the control. Generally, ULL and LL oils had lower percentages of polar compounds than did the control, providing a frying life 2 days longer than the control and ~30% increase in frying time. A trained sensory panel evaluated the French fries on days 2, 5, and 6. Buttery and potato flavors decreased, and rancid and painty flavors increased over frying time for all products. Rancid flavor was highest in the fries from the control oil. Overall, the ULL and LL oils performed better than did the control oil and ULL tended to perform better than the LL.     

Evaluation of Physico-Chemical and Sensory Quality During Storage of Soybean and Canola Oils Packaged in PET Bottles

The objective was to evaluate the quality of soybean and canola oils packaged in PET bottles during their shelf life. Considering the limit for the peroxide value established by Brazilian legislation the soybean and canola oils were outside the specification at between 75 and 165 days of storage, respectively, that is, before the end of the period of validity established by the producer (6 months and 1 year, respectively). The sensory analysis revealed alterations in the oil attributes of ‘aroma’ and ‘taste’ at between 180 and 300 days of storage, although the grades did not reveal significant alterations or a reduction in the acceptance of the products. The results obtained indicate that the physico-chemical quality parameters of soybean and canola oils produced in Brazil are outside the specification before the end of the validity period declared by the producers, the critical parameters being the peroxide and acid indices.     

Degradation and Nutritional Quality Changes of Oil During Frying

The changes in regular canola oil as affected by frying temperature were studied. French fries were fried intermittently in canola oil that was heated for 7 h daily over seven consecutive days. Thermo-oxidative alterations of the oil heated at 185 ± 5 or 215 ± 5 °C were measured by total polar components (TPC), anisidine value (AV), color components formation, and changes in fatty acid composition and tocopherols. Results showed that TPC, AV, color and trans fatty acid content increased significantly (P < 0.05) as a function of frying temperature and time. The oil polyunsaturated fatty acids (PUFA) decreased in direct proportion to frying temperature and time. After 7 days of frying, the amount of PUFA was reduced by half and the trans isomers contribution increased 2.5 times during frying at 215 °C. Of the parameters assessed, total polar component and color had the highest correlation, with correlation coefficients of 0.9650 and 0.9302 for frying at 215 and 185 °C, respectively. TPC formation correlated inversely with the reduction of tocopherols.     

Frying stability of canola oil in presence of pumpkin seed and olive oils

Frying performance of canola oil (CO) was investigated in the presence of 5, 10, and 15% levels of virgin olive oil (VOO) and pumpkin seed oil (PSO) during frying of potatoes at 180°C. Acid value, carbonyl value, total polar compounds content, and total tocopherols content of the oil samples were determined during the frying process. VOO and PSO addition improved the frying stability of the CO. Frying performance of the CO increased more in the presence of PSO than in the presence of the VOO. The PSO levels higher than 5% exerted pro‐oxidant effects, indicating the necessity of investigation at lower levels. The better antioxidative effect of PSO was attributed to its probably different phenolic composition.     

Antioxidant Activity of Sesamol in Soybean Oil Under Frying Conditions

Antioxidant activity of sesamol was investigated in soybean oil using a miniaturized frying experiment with potato cubes fried at 180 °C. Oxidation of soybean oil was determined by gel permeation chromatography for polymerized triacylglycerols and by ¹H-NMR spectroscopy for reactions at reactive sites of soybean oil molecules including olefinic, bisallylic and allylic protons during frying. Sesamol showed lower antioxidant activity than 0.02 % (w/w) tert-butylhydroquinone (TBHQ) at the same molar concentration. Higher concentrations of sesamol provided better antioxidant effects indicating that no prooxidant activity occurred. Sesamol in this frying test showed better results than 0.02 % TBHQ when the concentration was as high as 0.66 % by weight. An HPLC experiment showed that the concentration of sesamol decreased sharply during frying. Thermogravimetric analysis indicated that sesamol is highly volatile and easily oxidizes when exposed to air. To overcome this problem, two multiple addition methods were evaluated in which sesamol was added portion by portion every hour. The multiple additions of divided portions of 0.66 % (w/w) sesamol maintained the concentration of sesamol at the minimum of 0.04–0.06 % throughout the frying process and showed improved antioxidant activity compared to one single addition of 0.66 % sesamol at the beginning of frying. One of the multiple addition methods showed 28, 18, 59, and 27 % less polymerized triacylglycerols and losses of olefinic, bisallylic and allylic protons, respectively, than 0.02 % TBHQ after 8-h frying. This study shows that sesamol can be used as an alternative for synthetic antioxidants for frying oil.     

Mid-Oleic/Ultra Low Linolenic Acid Soybean Oil: A Healthful New Alternative to Hydrogenated Oil for Frying

To determine the frying stability of mid-oleic/ultra low linolenic acid soybean oil (MO/ULLSBO) and the storage stability of food fried in it, tortilla chips were fried in MO/ULLSBO, soybean oil (SBO), hydrogenated SBO (HSBO) and ultra low linolenic SBO (ULLSBO). Intermittent batch frying tests were conducted up to 55 h of frying, and then tortilla chips were aged up to 4 months at 25 °C. Frying oils were analyzed for total polar compounds to determine the frying stability of the oil. Tortilla chips were analyzed for hexanal as an indicator of oxidative deterioration and by sensory analysis using a trained, experienced analytical panel. Results showed no significant differences between the total polar compound levels for MO/ULLSBO and HSBO after 55 h of frying, indicating a similar fry life. However, total polar compound levels for ULLSBO and SBO were significantly higher than for either MO/ULLSBO or HSBO, indicating a lower oil fry life. Hexanal levels in aged tortilla chips fried in SBO were significantly higher than in chips fried in any of the other oils. Tortilla chips fried in MO/ULLSBO and HSBO had significantly lower hexanal levels than in chips fried in ULLSBO. A sensory analysis of rancid flavor intensity showed similar trends to those for hexanal formation. The chips fried in SBO had the highest rancid flavor intensity, with significantly lower hexanal levels in chips fried in HSBO and MO/ULLSBO. Based on these results, MO/ULLSBO not only had a good fry life but also produced oxidatively stable fried food, and therefore would be a healthful alternative to HSBO. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Effect of Tocopherols on the Anti-Polymerization Activity of Oryzanol and Corn Steryl Ferulates in Soybean Oil

Steryl ferulates (SFs) are ferulic acid esters of phytosterols and/or triterpene alcohols which have potential as frying oil antioxidants. The objective of this study was to evaluate the anti-polymerization and antioxidant activity at frying temperatures of corn steryl ferulates (CSFs), rice steryl ferulates (oryzanol), and a mixture of CSFs with oryzanol, alone and with tocopherols. Antioxidant activity was measured by the reduction of polymerized triacylglycerol formation, and loss of olefinic and bisallylic protons from fatty acid double bonds by ¹H NMR. CSFs and oryzanol slowed the oxidation and polymerization of soybean oil triacylglycerols heated to 180 °C more effectively than a mixture of alpha and gamma tocopherols. CSFs were more effective at preventing polymerization than oryzanol, but when oryzanol was combined with tocopherols, they all had similar antioxidant activity. In addition, tocopherols had a protective effect on SFs. Corn SFs were degraded more quickly during heating than oryzanol, however, the phytosterol constituents of corn SFs, sitostanol and campestanol, were actually more resistant to degradation compared to the phytosterol constituents of rice SFs. Results demonstrate that corn and rice SFs may be effective antioxidants for use in frying oils, and that their activity is enhanced in the presence of tocopherols.     

Rapid Determination of Degradation in Frying Oils with Near-Infrared Spectroscopy

Measures of free fatty acids (FFA), total polar materials (TPM), and conjugated dienoic acids (CDA), typical indices of oil degradation, were analyzed in daily oil aliquots taken from soybean oils with different linolenic acid concentrations used to fry French fries. The oils also were scanned with a reflectance near-infrared spectrometer using a wavelength range of 350–2,500 nm. By using partial least squares and one-out cross validation, calibrations were developed to quantitatively determine FFA, TPM, and CDA by near-infrared spectroscopy (NIRS). The coefficients of determination (R ²) when compared to the standard methods were 0.973 for FFA, 0.984 for TPM, and 0.902 for CDA. NIRS was an accurate and fast method to determine FFA, TPM, and CDA in oxidized oils. The ability to obtain different parameters simultaneously makes NIRS a potentially valuable tool for food quality assurance.     

Minor Constituents in Canola Oil Processed by Traditional and Minimal Refining Methods

The minimal refining method described in the present study made it possible to neutralize crude canola oil with Ca(OH)₂, MgO, and Na₂SiO₃ as alternatives to NaOH. After citric acid degumming, about 98 % of the phosphorous content was removed from crude oil. The free fatty acid content after minimal neutralization with Ca(OH)₂ decreased from 0.50 to 0.03 %. Other quality parameters, such as peroxide value, anisidine value, and chlorophyll content, after traditional and minimal neutralization were within industrial acceptable levels. The use of Trisyl silica and Magnesol R60 made it feasible to remove the hot-water washing step and decreased the amount of residual soap to <10 mg/kg oil. There were no significant changes in chemical characteristics of canola oil after using wet and dry bleaching methods. During traditional neutralization, the total tocopherol loss was 19.6 %, while minimal refining with Ca(OH)₂, MgO, and Na₂SiO₃ resulted in 7.0, 2.6, and 0.9 % reductions in total tocopherols. Traditional refining removed 23.6 % of total free sterols, while after minimal refining free sterols content did not change. Both traditional and minimal refining resulted in almost complete removal of polyphenols from canola oil. Total phytosterols and tocopherols in two cold-pressed canola oils were 774 and 836 mg/100 g, and 366 and 354 mg/kg, respectively. The minimal refining method described in the present study was a new practical approach to remove undesirable components from crude canola oil meeting commercial refining standards while preserving more healthy minor components.     

Properties of Oleogels Formed With High‐Stearic Soybean Oils and Sunflower Wax

In an effort to develop alternatives for harmful trans fats produced by partial hydrogenation of vegetable oils, oleogels of high‐stearic soybean (A6 and MM106) oils were prepared with sunflower wax (SW) as the oleogelator. Oleogels of high‐stearic oils did not have greater firmness when compared to regular soybean oil (SBO) at room temperature. However, the firmness of high‐stearic oil oleogels at 4 °C sharply increased due to the high content of stearic acid. High‐stearic acid SBO had more polar compounds than the regular SBO. Polar compounds in oil inversely affected the firmness of oleogels. Differential scanning calorimetry showed that wax crystals facilitated nucleation of solid fats of high‐stearic oils during cooling. Polar compounds did not affect the melting and crystallization behavior of wax. Solid fat content (SFC) showed that polar compounds in oil and wax interfered with crystallization of solid fats. Linear viscoelastic properties of 7% SW oleogels of three oils reflected well the SFC values while they did not correlate well with the firmness of oleogels. Phase‐contrast microscopy showed that the wax crystal morphology was slightly influenced by solid fats in the high‐steric SBO, A6.     

Effects of Linalyl Oleate on Soybean Oil Flavor and Quality in a Frying Application

Bread pieces were fried at 180 °C in soybean oil (SBO) containing no additives (control), 0.1% linalyl oleate (LO), or 10 ppm methyl silicone (MS). After 2 h of heating, the MS-containing oil was the most stable, followed by the oil with LO and the control, based on conjugated dienoic acid percentage (CD) and the ratio of linoleate%/palmitate%. Oil extracted from the fresh fried bread showed similar, but not significant, trends for CD and PV. Fresh and stored (60 °C, 2 days) bread fried in LO-containing oil had less hexanal than the other two treatments, and the stored LO bread had less t,c- and t,t-2,4-heptadienal than the control. Fresh bread fried in LO-containing oil had a less rancid flavor than did the other two treatments, and the LO treatment had less fishy flavor than the control. In stored bread, the MS treatment was less rancid than the control. In oil extracted from the stored bread, the amounts of t,c-2,4-heptadienal and 2-decenal correlated (p ≤ 0.05) with the amounts of individual unsaturated fatty acids and with CD, but only t,c-2,4-heptadienal correlated with the PV. The t,c-2,4-heptadienal correlated with individual Polyunsaturated fatty acids (PUFA) in freshly fried bread. In general, oil and fried bread had improved flavor quality and/or oil stability when they contained MS or LO.     

Accumulation of 5-Hydroxymethylfurfural in Oil During Frying of Model Dough

5-Hydroxymethylfurfural (HMF), a thermal process contaminant, forms in food during frying as a result of the Maillard reaction and caramelization. Owing to its chemical properties, HMF formed in foods during frying partially transfers into frying oil. This study aimed to investigate the accumulation of HMF in oil during repetitive frying operations. A model dough composed of 25 % of glucose was fried at 160, 170, 180 °C for 50 frying cycles. Apart from total polar compounds (TPC), accumulation of HMF was determined in oils during repetitive frying operations. Increasing frying temperature also increased the amount of HMF formed in dough, and those transferred to oil. Prolonging frying cycles to 150, increasing amount of dough being fried to 100 g and frying time to 10 min caused the TPC content to reach 25 % at the 130th frying cycle at 180 °C. Under the same frying conditions, the concentration of HMF showed a rapid increase at the first 10th frying cycle. Its increase was at a slower rate until the 50th frying cycle reaching a plateau level exceeding 5.0 mg/L. The results revealed that HMF transferred and accumulated in the frying oil during repetitive frying. The HMF concentration exceeding 5.0 mg/L in oil may be considered as an indicator for heavily used frying oil. Correlation between TPC and HMF contents of frying oil showed no linear correlation.     

Carob Fruit Polyphenols Reduce Tocopherol Loss,Triacylglycerol Polymerization and Oxidation in Heated Sunflower Oil

Heated oils may contain potentially toxic altered compounds. A denatured carob fiber, very rich in non-extractable tannins (Exxenterol^®), exhibits antioxidant activities in in vitro experiments. The present study was designed to evaluate in sunflower oil (SO) heated to frying temperature, the protective effect on oil thermal oxidation and polymerization of adding 10 mg Exxenterol/kg oil (SO-10) and 50 mg Exxenterol/kg oil (SO-50). After 2, 8 and 16 h at 180 °C, SO displayed a relevant increase in triacylglycerol-derived polar material (PM) and polymer contents and a decrease in α-tocopherol concentrations. Thermal oxidation changes were significantly checked in SO-50 throughout the 16-h heating, while SO-10 only displayed protection from thermal oxidation during the first 2 h of heating. Oil frying-life was doubled because formation of PM and polymers was inhibited by more than 50%. Results clearly show that this non-extractable tannin-rich fiber can be successfully employed as an additive to significantly prolong sunflower oil frying-life, and thus decrease the potential toxicity of the heated oil.     

Monitoring of Changes in Composition of Soybean Oil During Deep-Fat Frying with Different Food Types

Changes in the composition of soybean oil during deep‐fat frying with wheat dough (WD) and chicken breast meat (CBM) were comparatively investigated using gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy (FTIR). The amounts of saturated fatty acids (FAs) and short‐chain FAs were increased. The amount of unsaturated FAs was decreased as the processing time increased. An increase in the amount of tetradecanoic acid and 9‐cis‐hexadecanoic acid was observed during the CBM frying only. The FTIR spectrum of frying oil was analyzed by extracting the entire information as the area ratios based on vibration absorptions of the specific functional groups. Changes in content of functional groups, namely cis C=C, trans C=C, C=O, C–O, O–H, and C–H, were studied by the FTIR‐based method. Based on the changes in the content of FAs and functional groups, soybean oil fried with CBM degraded more quickly than that fried with WD. Moreover, good linear correlations between the change in contents of functional groups and the mass percentages of FAs were also observed. The FTIR‐based method could be used in real time to monitor the quality of frying oil during the deep‐fat frying.     

Effect of Polysoap on the Physical and Tribological Properties of Soybean Oil‐Based Grease

Soybean oil (SBO)‐based grease, containing polysoaps synthesized from polymeric epoxidized soybean oil (PESO), were investigated. Greases were prepared using a mixture of lithium soap and triethanolammonium polysoap. Grease properties investigated were hardness, using the cone penetration procedure (ASTM D217); oxidation stability, using the pressurized differential scanning calorimetry (PDSC) method (ASTM D‐5483); and friction and wear, using a four‐ball tribometer (ASTM D‐2266). Penetration data showed that grease formulated in the presence of polysoap was harder than that without polysoap, and this was attributed to the cross‐linking in the polysoap structure, which was expected to provide higher resistance to deformation. The PDSC results indicated that the onset temperature of grease formulated with 3.8 and 7.3 wt% polysoap increased by 8 and 12°C, respectively, compared to grease without polysoap. The coefficient of friction of grease formulated with polysoap was much lower (0.015) than grease without polysoap (0.034).