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The current study investigates to what extent the reaction products of thermal degradation directly influence acrylamide formation in French fries. The frying tests at 170 and 180 °C are carried out with rapeseed oil for 32 h with 128 frying cycles. Acrylamide content in French fries is determined by LC-MS/MS. Oxidative and thermal degradation is followed by measuring total polar compounds (TPC), di- and polymerized triacylglycerols (DPTG), monomer oxidized triacylglycerols (MONOX), p-anisidine value (AnV), mono and di-acyl-glycerols (MAG and DAG), acid value (AV), epoxy fatty acids, iodine value (IV), saponification value, and fatty acid composition. During frying, the nature and degradation level of the frying medium have a direct impact on acrylamide formation. It can be shown that the pH-dependent reaction is strongly inhibited at acid values above 0.5 mg KOH g−1 oil. Acidity measured as AV or FFA is mainly caused by oxidation, and less so by hydrolysis of triacylglycerols (TAG) as assumed up to now. Obviously, acid functional groups formed by oxidation of unsaturated fatty acids bound in TAG can act not only as catalyst for dimerization of TAG but also interact with asparagine as most important precursor for acrylamide formation so that no reaction with carbonyl groups for the formation of acrylamide is necessary. Practical applications: The same acidic functional groups that are known to catalyze the formation of dimeric TAG under frying conditions (160–190 °C, access of oxygen) in a nonradical mechanism apparently can also deactivate asparagine by protonization as a potential precursor for the formation of acrylamide. It is recommended not to reduce acidity of used frying oil by active filter aids below AV ≥ 0.5 as it helps to reduce acrylamide contamination of fried food.

Processing of edible oils during refining of the crude oil, or when used in frying, often exposes the oils to thermal and oxidative stresses. However, because of weaknesses inherent in their chemical structure, oils subsequently undergo structural decomposition and transformation in response to thermooxidative stresses. Whereas some of the decomposition products from the processed oils confer some value additions to the oils and the foods prepared in them (e.g. flavor, color, texture, and even stability), a number of edible oils' degradation products are known to be potentially toxic, and at reasonably high quantity, can compromise the health and wellbeing of consumers. This article describes the sources and updated knowledge on major toxic compounds that are generated during high temperature processing and usage of vegetable oils.

Phloridzyl octadecanoate was prepared by enzymatic reaction between the native phloridzin in Canadian crabapple (Malus baccata) extract and octadecanoic acid in the presence of Candida antarctica lipase. The antioxidant activity of the modified extract was assessed in rapeseed oil during accelerated storage at 65°C and frying at 180°C. Addition of 0.1% modified extract to refined, bleached, and deodorized rapeseed oil significantly improved storage stability with 40.7% decrease in the formation of lipid hydroperoxides at the end of the 7-day storage compared to rapeseed control sample without extract; however, no significant difference was observed in the potency of the modified extract and that of the native extract. On the contrary, the modified extract offered markedly better protection to the rapeseed substrate during frying, inhibiting polar component formation, and polymerization of triacylglycerol by up to 44%, compared to 26% by the native extract. At the end of the frying, French fries prepared in the presence of modified extract retained significantly more tocopherols than those prepared with the native extract indicating better protection of the oil's endogenous antioxidants by the modified phenolic extract. Practical applications: Poor lipophilicity is a major challenge to the application of natural polyphenolic compounds in edible oils. Equally challenging is the development of natural antioxidants that can maintain effectiveness under the stringent dynamic conditions of frying. Results from the current study demonstrated the possibility of overcoming these challenges, providing food processors with lipophilic natural antioxidants of practical importance in the frying process. Improving the lipophilicity of the polyphenolic components of Canadian crabapple's extract resulted in enhanced antioxidant and antipolymerization activities during frying, with consequent decreased in: Total polar materials (TPM); di- and polymerized triacylglycerols (DPTG); formation of non-volatile carbonyl compounds assessed by the anisidine value (AnV); and rate of endogenous tocopherol degradation. However, no change in activity was observed under storage conditions.

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.

Wild rice is a nutritious grain that was an important crop for ancient North Americans, and then dispersed into eastern Asia. Recognized as a whole grain in 2006, wild rice is a rich source of minerals, vitamins, protein, starch, dietary fiber, and various phytochemicals. It is low in fat, with a beneficial fatty acids profile. Additionally, wild rice is gluten free. Due to its unique nutritional value, the crop should be promoted as a healthy food source. Although North American wild rice has become very popular, and is widely available in supermarkets and resturaunts, its health-promoting properties have not been widely investigated. To date, only a few in vivo and in vitro studies demonstrated antioxidant- and lipid-lowering effects of wild rice. In this chapter, the potential health-promoting properties are summarized.

The prevailing stigmatization of synthetic antioxidants and the inefficiency of endogenous antioxidants like tocopherols during high temperature processing of edible oils necessitate the search for effective natural antioxidants. Here, polyphenolic extracts from chokecherry and hawthorn fruits were screened for possible antioxidative application in fats/oils. Extracts were successively partitioned on sephadex columns and fractions were screened for radical scavenging activity using DPPH and beta-carotene assays. Furthermore, sunflower oil fortified with extracts was assessed for stability using accelerated storage at 65 degrees C, Rancimat at 120 degrees C. and frying at 180 degrees C. Phenolic extracts showed significantly high radical scavenging and antioxidant activity in the oil. At the end of storage, hydroperoxide formation in sunflower oil was reduced by up to 50%, and the induction period significantly increased in the presence of extracts. Similarly, a significantly high frying stability was observed for the fortified samples, suggesting that the phenolic extracts can offer effective natural alternative to synthetic antioxidants during frying. (C) 2014 Elsevier Ltd. All rights reserved.

Canadian condiment yellow mustard seeds (also called white), oriental and brown mustard seeds and flour extracts and commercially produced Indian mustard oils were examined for bioactive phenolics primarily to identify the antioxidant properties. Phenolic compounds, namely sinapic acid, sinapoyl glucose and canolol, were quantified using high-performance liquid chromatographic (HPLC) coupled with a diode array detector (DAD). Canolol was detected and confirmed in trace amounts for the first time in commercial oils that had not been preheated specific for canolol production, most likely due to heat applied during processing. Sinapic acid, sinapine and canolol derived from unheated/unroasted mustard seeds and canola extracts were confirmed utilizing HPLC-DAD, ultra-performance liquid chromatography-tandem-mass spectrometry (UPLC-tandem-MS) and nuclear magnetic resonance (NMR) spectroscopy. Practical applications: Oilseeds canola and mustard contain significant amounts of phenolic compounds, principally sinapic acid derivatives. The level and functionality of these phenolic is highly influenced by the processing conditions. In the current study, the phenolic composition of some commercial mustard seed, oil, meal and flour samples were profiled with special focus on the occurrence of canolol, the decarboxylation product of sinapic acid. This study suggests that optimizing the crushing, pressing, or extraction steps during processing is crucial to enrich mustard and canola products with benefits associated with these bioactives, especially canolol. The existence of sinapic acid derivatives was confirmed in the 70% aqueous methanolic extracts of commercial mustard products such as deheated mustard flour and oil. Extracts of mustard, in addition to canola, contain significant amounts of phenolics, mainly sinapine. Traditional ghani pressing, cold pressing and/or screw expeller pressing hold potential for enriching mustard and sinapate-rich oil with benefits associated with canolol.

In the present study, phenolic extracts and fractions from Canadian rowanberry ( Sorbus aucuparia ) and crabapple ( Malus baccata ) were screened for antioxidant activity using DPPH radical scavenging activity, and β-carotene bleaching assays. Furthermore, rapeseed oil was supplemented with extracts/fractions and performance was assessed during accelerated storage at 65 °C, under Rancimat at 120 °C, and during frying at 180 °C. A number of phenolic fractions showed significantly higher radical scavenging and antioxidant activity in the oil than the synthetic antioxidant, butylated hydroxytoluene (BHT). At the end of the 7-day storage, the peroxide value was reduced by up to 42% in the presence of extracts. The extent of thermooxidative degradation was significantly lower in oils fortified with the fruit extracts, with fractions from Sorbus species being more effective. Results from the present study suggested that polyphenolic extracts from these fruits can offer effective alternative to synthetic antioxidants during frying and storage of vegetable oils.

In the present work a fast and reliable laboratory protocol allowing a holistic statement about thermo-oxidative structural changes of fats and oils at ambient temperatures, under accelerated conditions using 110°C and under elevated temperature usually used for frying at 170°C is proposed. The results demonstrate that two different routes of degradation may be responsible for fat deterioration at elevated temperatures. Depending on the temperature (at 20, 110, or 170°C) the composition of polar compounds changed. The content of di- and polymerized TAGs increased with time at elevated temperature, e.g., frying whereas the formation of oxidized products dominates at 110°C or lower. These different reaction mechanisms may explain the discrepancy between practical experiences during frying and the estimated oxidative resistance of fats and oils using accelerated tests like Rancimat or OSI. Practical applications: Both the amount of total oxidized monomeric TAGs called total oxidized products (TOP) and the amount of di- and polymerized TAGs (DPTG) can be used to describe the fat degradation at all stages. These parameters are less dependent on the fat composition but proportional to the heating time and applied temperature. A procedure is proposed to compare thermal and oxidative stability of vegetable oils and effectiveness of oxidative stabilizing agents. Heating apparatus to simulate fat degradation at 110 and 170°C with and without access of oxygen (20 L/h) to monitor oxidation and structural decomposition of fats and oils.

In this study, the effectiveness of phenolic extracts from Rosa woodsii hip with seed (Rosae pseudofructus cum fructibus) in protecting vegetable oils against oxidative and thermal deterioration was assessed during accelerated storage of canola oil at 65°C, Rancimat at 120°C, and frying at 180°C. At the end of the 7-day storage, formation of lipid hydroperoxides was 2.5 times higher in control canola oil compared to the fortified sample. Accumulation of polar components, polymerized TAGs and other secondary degradation products during frying was reduced by up to 30% in the presence of the applied phenolic extracts. Similarly, the oxidative stability of canola oil significantly increased in the presence of extract as measured by Rancimat induction period (IP). HPLC-MS analysis indicated that quercetin, catechin, and gallic acid were the major phenolic constituents of Rosa woodsii fruit extract, and are possibly the active antioxidant compounds of the extract. Practical applications: Oxidation of fats and oils or fatty fractions of foods is one of the major reasons for the deterioration of food. Therefore the search for highly effective antioxidants from natural sources to stabilize frying oils or food preparations is an ongoing story. The present paper demonstrates that phenolic extracts from Rosa woodsii Lindl (Rosaceae) can improve the frying and storage stability of edible oils. The findings can help food processors to improve quality and safety of food. Phenolic extract from Rosa woodsii improved the thermo-oxidative stability of canola oil.

Lipophilic components of three herbs, sage, thyme, and rosemary, were extracted into refined rapeseed oil by continuous stirring at 30°C for 24 h. The oxidative and frying stability of the flavored oil was assessed by Rancimat at 120°C and frying of French fries at 175°C, respectively. In comparison to the control with an induction period of 4.1 h in the Rancimat test, the treatment with thyme, rosemary, and sage resulted in induction periods of 5.3, 9.3, and 11.0 h, respectively, corresponding to stabilization factors of 1.1, 2.0, and 2.4, respectively. In contrast to the oxidative stability at 120°C, treated oils exhibited significantly lower frying stability, compared to the control. For instance, whereas rapeseed oils treated with plant materials exceeded the 12% regulatory limit for oligomeric triacylglycerols within 20 h of frying, the limit was only exceeded after 25 h of frying in the control. However, despite the significantly higher level of thermo-oxidative degradation in the flavored oils, the sensory quality of the French fries prepared in these oils remained still acceptable within the frying time of 32 h whereas fries prepared in the control oil were judged unacceptable. Further, endogenous tocopherols were better protected in the treated oils. Practical applications: The prolongation of the shelf life of frying oils is of great economical and commercial importance. Thus, food processors are very interested in the improvement of the thermal stability of frying oils, which may provide remarkable savings. On the other side more and more flavored oils come to the market. Therefore it is important to have more information about the oxidative and thermal stability of such oils.

Frying is a very complex process and the applied conditions often overwhelm most endogenous and added antioxidants. Synthetic antioxidants such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and tert-butylhydroquinone (TBHQ) are often added to processed oils to retard oxidative degradation during storage and frying; however, beside their poor performance under frying conditions, consumers' acceptance of synthetic antioxidants remains negative due to their perceived detrimental effect on human health. Consequently, there is a growing interest in the search for effective natural antioxidants for frying applications, notably, from phenolic components of common spices and herbs. The present study provides an overview of the literature on natural antioxidants, sources, and their performance under frying conditions. Practical applications: Sources and performance of natural antioxidants during frying were reviewed. Despite abundance of data on the radical scavenging activity and antioxidant potency of some natural antioxidants under storage conditions, there is still a dearth of information on their activity during frying. This study revealed a number of under-exploited sources of natural antioxidants that could be used to improve the stability of frying oils.

The effect of pre-formed lipid hydroperoxides, breading, and battering ingredients on pigment formation and thermo-oxidative degradation of oil during institutional frying was evaluated. The food ingredients were fried intermittently in canola oil heated for 8 h daily over 4 consecutive days at 185 ± 5°C. Color component formation, total polar components (TPC), and tocopherols were measured. Glycine-enriched whey protein fried in 1% oxidized canola oil contributed most significantly to oil darkening with a rate ten times that of the control sample. Using whey protein as a base for battering caused the most significant color changes and thermo-oxidative deterioration. Glucose and glycine are two minor ingredients that also contribute to color formation in oil. Breading materials were prone to cause a more significant amount of oil deterioration when compared to battering ingredients most likely due to excess loose breading particles falling into the oil during frying. Practical applications: The present study evaluated the effect of some components of food coatings on the stability and pigment formation of the frying oil. The results suggest the need to optimize the protein component of coating materials and ensure that the amounts of loose particles on breaded products are adequately minimized. This information will assist institutional frying operators and other relevant industries in product development and food preparation with the view of optimizing performance of the frying oil.

The frying performance of rapeseed, soybean, and sunflower oils with modified fatty acid composition, and palm olein (PALMO) was compared during a rotational frying operation. The frying was conducted at 185 ± 5°C for 6 days where French fries, battered chicken, and fish sticks were fried in succession. At the end of the frying period, high-oleic rapeseed and sunflower oils exhibited a significantly higher frying stability than PALMO and other modified oils, based on total polar components (TPC), polymers, and non-volatile carbonyl compounds formation (anisidine value (AV)). The rate of TPC formation was 2.9, 2.9, 3.2, 3.2, and 3.4% per frying day for high-oleic low-linolenic rapeseed (HOLLRAP), high-oleic sunflower (HOSUN), mid-oleic sunflower (MOSUN), low-linolenic soybean (LLSOY), and PALMO, respectively. Although the contents of free fatty acids (FFA) in the used oils were significantly below the regulatory discard level, in PALMO formation of these compounds was 1.7 times higher compared to the modified oils. Color component formation and tocopherol degradation were also observed to be the highest in palm olein. A 15-member consumer panel awarded HOLLRAP and HOSUN the highest overall sensory acceptance scores, while for LLSOY and PALMO the lowest. Practical applications: Although several frying oils are available in today's market, only a few of them can deliver satisfactory performance during extended frying operation. Thus, the search for the ideal frying oils/fats is an ongoing task. The present study assessed frying performance in the quest for the appropriate frying oils/fats in order to deliver healthy fried products with optimized nutritional qualities.

Free radicals are formed as a result of cellular processes and play a key role in predisposition to and development of numerous diseases and of premature aging. Recently, we reported the syntheses of a number of novel phenolic antioxidants for possible application in food industry. In the present study, analyses of the cellular processes and molecular gene expression effects of some of the novel antioxidants in normal human tissues and in cancer cells were undertaken. Results indicated that whereas the examined antioxidants showed no effects on morphology and gene expression of normal human oral and gingival epithelial tissues, they exerted a profound cell killing effect on breast cancer cells, including on chemotherapy-resistant breast cancer cells and on oral squamous carcinoma cells. Among the tested antioxidants, N-decyl-N-(3-methoxy-4-hydroxybenzyl)-3-(3,4-dihydroxyphenyl) propanamide and N-decyl-N-(3,5-dimethoxy-4-hydroxybenzyl)-3-(3,4-dihydroxyphenyl) propanamide were the most promising, with excellent potential for cancer treatment. Moreover, our gene expression databases can be used as a roadmap for future analysis of mechanisms of antioxidant action.

Minor components are the non-triacylglycerol constituents of oil and constitute up to 5% of the total lipid composition. Though minor in composition, they can exert major influence on the performance of oil during frying. The effect of the minor components on frying performance depends on their chemical nature, composition and amount in the oil. Among these minor components tocopherols, phytosterols, phospholipids, γ-oryzanol, lignans, phenolics, and carotenoids are the most important. Here, their effect on the frying performance of edible oils is discussed.

γ-Oryzanol, a natural mixture of ferulic acid esters of triterpene alcohols and sterols, are an important bioactive components present in rice bran oil. In light of the recent increase in the popularity of wild rice among consumers, and the possibility of a direct relationship between γ-oryzanol composition and its bioactivity, the oryzanol profile of major wild rice (Zizania palustris) grown in North America was studied and compared to regular brown rice (Oryza sativa L.). A total of twenty-three γ-oryzanol components were separated, identified and quantified by HPLC coupled to an Orbitrap MS. The distribution of individual γ-oryzanols was similar for all the wild rice but significantly different from those of the regular brown rice. Unlike in the regular brown rice, a significant amount of steryl caffeate and cinnamate were found in the wild rice samples. Generally, the amounts of γ-oryzanol in the wild rice were higher compared to the regular brown rice, 1,352 vs. 688 μg/g. The results from this study showed that wild rice had a more diverse γ-oryzanol composition and the higher amounts compared to the regular brown rice.

Fourteen cyclolinopeptides (CLPs) from flaxseed oil and meal were separated, identified and quantified by HPLC coupled to an Orbitrap MS. The oxidative stability of the cyclolinopeptides was assessed during storage of flaxseed oil and meal. A significant decrease in the amounts of the methionine containing CLPs, namely CLP-B, CLP-J and CLP-M, and a concurrent increase in the amounts of methionine sulfoxide containing CLPs, such as CLP-C, CLP-E and CLP-G were observed. The cyclolinopeptides with two methionine units, CLP-L and CLP-M, exhibited the greatest decrease, followed by CLP-J, the major flaxseed oil bitter taste precursor, and CLP-B, a biologically active cyclolinopeptide. At the end of the storage period, the amount of the bitter CLP-E increased fourfold in the oil while the immunosuppressive cyclolinopeptides A remained unchanged. No significant changes in the amount of each of the CLPs were observed in the stored flaxseed meals. A fast and reliable procedure has been developed for quantitative analysis of cyclolinopeptides. Due to the high predisposition of methionine containing cyclolinopeptides to oxidation and the easiness of CLPs’ quantification with the proposed method, it is possible to reliably assess the extent of flaxseed meal and oil oxidation.

Twelve novel dihydro-caffeic acid amides were synthesised in good yields and fully characterised by 1H NMR, 13C NMR, and MS. Their radical scavenging activities were assessed by DPPH assay. Additionally, their abilities to protect polyunsaturated oils under accelerated storage and frying conditions were evaluated. All the new compounds possessed significantly higher radical scavenging activities than α-tocopherol and butylated hydroxytoluene (BHT). The radical scavenging activity of N-decyl-N-(3,5-dimethoxy-4-hydroxybenzyl)-3-(3,4-dihydroxyphenyl) propanamide was 1.7 and 4 times higher than α-tocopherol and BHT, respectively. At the end of the storage period, the respective amounts of hydroperoxides in canola oil triacylglycerols (CTAG) fortified with α-tocopherol and BHT was 6.1 and 1.4 times higher, respectively, than CTAG containing the amide. The frying test showed that CTAG containing N-decyl-N-benzyl-3-(3,4-dihydroxybenzyl) propanamide was 1.3, 1.4, and 1.6 times more stable compared to oil fortified with dihydro-caffeic acid, α-tocopherol and BHT, respectively, as assessed by the amounts of the total polar compounds. Moreover, these compounds were remarkably thermally stable, making them suitable for frying applications.

The ability of selected phenolic acids to improve the frying performance of canola oil was evaluated in a frying test. The frying performance of the oil was assessed by analysis of total polar components (TPC), level of 4-hydroxynonenal (HNE), and the rate of formation of volatile carbonyl compounds (VCC). All the tested phenolic acids; ferulic acid (FA), caffeic acid (CA), dihydrocaffeic acid (HCA), gallic acid (GA), and vanillic acid (VA) significantly increased the frying performance of canola oil triacylglycerols (CTG). At the end of the frying test, the amount of TPC in CTG was 22.9 ± 1.0% compared to a maximum of 18.8 ± 0.8% in CTG fortified with the phenolic acids. Similarly, the level of HNE was reduced by up to 45% when it was supplemented with phenolic acids. The results showed that ethyl ferulate (EF) was a better antioxidant than FA under frying conditions; HCA offered a slightly better protection than CA; and the cinnamic acid derivative, FA was better than VA, its benzoic acid analogue. A significant synergy was observed between phenolic acids and the sterol fraction isolated from canola oil. The observed synergy was attributed to the possible formation of steryl phenolates during the frying test. Practical applications: The poor thermal stability of polyunsaturated oils limits their application for prolonged frying. PUFA offer important health benefits and can improve nutritional value of fried foods. Contrary to the commonly applied synthetic antioxidants, the phenolic acids tested in this study often are part of endogenous oil components present in oilseeds and also in some oils, and are known for their positive health benefits. Thus, the simple phenolic acids, especially the cinnamic acid derivatives may be applied as potent antioxidants to protect oils during thermal processes used for food production.

Novel phenolic antioxidants: 2a (6′-hydroxy-2′,5′,7′,8′-tetramethylchroman-2′-yl)methyl 3-methoxy-4-hydroxycinnamate, 2b (6′-hydroxy-2′,5′,7′,8′-tetramethylchroman-2′-yl)methyl 3,5-dimethoxy-4-hydroxycinnamate, 2c (6′-hydroxy-2′,5′,7′,8′-tetramethylchroman-2′-yl)methyl 3,4-dihydroxycinnamate, and 3 (6-hydroxy-2,5,7,8-tetramethylchroman-2-yl)methyl (6′-hydroxy-2′,5′,7′,8′-tetramethylchroman-2′-carboxylate) have been prepared in good yields and fully characterized by 1H and 13C NMR, and HRMS. Their radical scavenging activities have been evaluated by DPPH and ORAC assays. Each of the synthesized antioxidants exhibited significantly higher radical scavenging activities than trolox and α-tocopherol. These novel antioxidants efficiently protected canola oil triacylglycerides (CTG) during accelerated storage and frying. Compounds 2c and 3 were significantly more efficient than α-tocopherol protecting CTG under accelerated storage. All new antioxidants were more efficient than α-tocopherol under frying conditions and present significantly higher thermal stability.

The endogenous minor components from canola, rice bran, sesame and palm oils including selected phospholipids, and various combinations of tocopherol isomers were tested during frying using canola oil triacylglycerols as the frying medium. Thermo-oxidative degradation was assessed by measurement of the total polar components, the rate of volatile carbonyl compounds and 4-hydroxynonenal formation. All the tested minor components protected to a different extent canola triacylglycerides from thermo-oxidative degradation during frying. No significant differences were observed in the protection of the triacylglycerides among all the tested tocopherol isomers and their mixtures. Irrespective of the composition of tocopherol homologous, an increase in the added amounts above 1,000 μg/g did not improve protection. Minor components isolated from rice bran and sesame oils offered better protection during canola triacylglycerides frying than endogenous minor components isolated from canola oil. When 0.2% phosphatidylcholine or phosphatidylethanolamine was added to the canola triacylglycerides, the amount of formed polar components decreased twice as compared to the tocopherol isomers. Accordingly, by optimizing the composition and the concentration of the endogenous minor components, the frying performance of oil can be significantly enhanced.

A rapid, effective test mimicking actual frying was developed to assess the frying performance of oils and fats using small size samples. To a small volume of the oil to be tested, a formulated food consisting of gelatinized potato starch, glucose and silica gel (4:1:1 w/w) were added and content heated at 185 ± 5 °C with mixing for 2 h. Thermo-oxidative degradation of the oil was assessed by the measurement of the total amount of polar components and their composition, including degradation of tocopherols. The developed fast test accurately mimics actual frying done using an institutional fryer as assessed by the accumulation and composition of total polar components and the amount of residual tocopherols. The validity of the test was assessed using the following oils: regular canola, high oleic– low linolenic canola, and high oleic sunflower. Comparison of data between the fast frying test and institutional frying revealed a lack of significant differences. The developed frying test provides reliable quantitative and qualitative data describing the performance of the frying oil/fat. The rapid frying procedure allows assessment of the frying performance of oils at the early stages of development where usually only small amounts of the sample are available and when a large number of samples have to be tested assessing effects of oil additives.

Acrylamide and 4-hydroxynonenal (HNE) are among the most detrimental compounds formed during high temperature processing of food. The effect of carbon dioxide blanketing (CDB) on the formation and accumulation in food of these compounds during deep-fat frying was investigated. French fries were fried for 7 h daily and for 7 days in canola oil at 185 ± 5°C without and with CO2 protection. The amount of acrylamide and HNE accumulated in the French fries were analyzed. Compared to standard frying conditions (SFC), frying under CDB reduced the amount of HNE by 62%. On the 3rd day of frying, the amount of acrylamide in fries fried under SFC was 3.3 times higher compared to frying with CO2 protection. Frying with carbon dioxide protection is an effective and practical way to impede formation of toxic components during deep-fat frying. To assess formation of HNE a simple, sensitive and reliable procedure for HNE analysis in frying oils and fried products was developed and evaluated. Practical applications: The toxicity of HNE and acrylamide, coupled with the increasing consumption of fried foods necessitates that measures be taken to reduce their formation and subsequent accumulation in fried foods. The frying method proposed in this study is very effective and requires only a simple modification to the fryer. Developed rapid and simple procedure for HNE analysis allows more accurate quantification.

The oxidative stability of liquid eggs enriched with very long-chain n-3 fatty acids and liquid regular eggs stored under refrigerated temperature, is investigated. Oxidized lipids can alter both nutritional and sensorial properties of foods. The extent of lipid oxidation is evaluated by quantification of total lipids, docosahexaenoic acid (DHA), and peroxide value (PV), but also by assessment of total tocopherols and γ-tocopherol losses. Additionally, the development of fishy off-flavor is evaluated. Results highlight significant differences between omega and regular liquid eggs stability. Although, the oxidative changes are observed in both types of liquid eggs, more susceptible to oxidation are omega liquid eggs. Practical Applications: Food enrichment with essential nutrients contributes to human health by providing the proper intake of essential nutrients. The results of this study suggest that fortification of eggs with highly unsaturated fatty acids should be in conjunction with the addition of natural antioxidants to retard undergoing oxidative changes. Liquid omega eggs are, unfortunately, more susceptible to oxidation than regular liquid eggs under simulated long time storage. The high concentration of unsaturated fatty acids improved their nutrition value but at the same time these products are less stable and unfavorable changes are more prominent. Therefore, the very long chain fatty acids in liquid omega eggs should be protected from undergoing deterioration. Although, the liquid omega eggs samples are stored at refrigerated temperature, significant changes are observed. The storage period led to a modification of the odor of liquid omega eggs, the increase in the fishy odor intensity is noticeable. And for the consumer, off-flavor is generally the first factor which will make the product unacceptable.

The effect of carbon dioxide blanketing (CDB) and vacuum frying (VF) on the frying performance of regular canola oil was evaluated. For 7 h daily and for 7 days French fries were fried in regular canola oil at 185 ± 5 °C without and with CDB and in a vacuum fryer. The extent of changes in the oil was assessed by analysis of total polar compounds (TPC), anisidine value (AV), color component formation and changes in composition of fatty acids and tocopherols. Frying under CDB reduced the amount of TPC by 54%, while 76% reduction was observed during VF compared to standard frying conditions (SFC). Similarly, lower oxidative degradation was observed when measured by AV. At the end of the frying period, the reduction in unsaturated fatty acid content was 3.8, 1.9 and 12.7% when frying under CDB, vacuum and SFC, respectively. The rate of tocopherol degradation was three and twelve times slower in VF when compared to CDB and SFC, respectively.

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.

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.

Phenolic extracts from Sorbus aucuparia (L.) were lipophilized in the presence of Candida antarctica lipase using octadecanol as the alkyl donor. The antioxidant activity of the lipophilized extract was assessed in refined, bleached and deodorized rapeseed oil during accelerated storage at 65 degrees C and frying at 180 degrees C. Rapeseed oil fortified with lipophilized extract showed significantly higher storage stability with 43% decrease in peroxide value at the end of the 7-day storage compared to rapeseed control sample without extract; however, no significant difference was observed in the performance of lipophilized extract and the native extract. On the contrary, the lipophilized extract exhibited markedly better protection against thermo-oxidative degradation during frying, inhibiting polar component formation and polymerization of triacylglycerol by up to 48%, compared to 30% by the native extract. At the end of the frying, French fries prepared in the presence of lipophilized extract had 7 times more phenolic compounds compared to fries prepared in the native extract indicating better solubilization of the phenolic compounds in the frying medium. Thus, lipophilization of phenolic compounds enhanced their protective activity in frying oil and improved the functionality of the prepared food. (C) 2014 Elsevier Ltd. All rights reserved.

Summary The aim of this work was to explore the feasibility and limits of analytical criteria to assess the sensory properties of used frying oils and different fried food. Over a period of two years, 148 used frying oils collected in restaurant, bakeries, fish caterers and industrial plants were analyzed for a wide range of parameters, including sensory tests, Total Polar Compounds (TPC), Dimerized and Polymerized Triacyl-Glycerols (DPTG), Monomeric Oxidized Triacyl-Glycerols (MONOX), Acid Value (AV), para-Anisidine-Value (AnV) and Iodine Value (IV). All methods were judged for their relevance, concerning the sensory quality of used frying oils categorizing the qualities as good or bad. The binary results were statistically evaluated using logistic logit regression. The statistical evaluation of the tests was used to calculate the probability of occurrence of off-flavors which allows determining the point of discard and finally the point where the oil is certainly totally abused. All levels of degradation for used frying oils regardless of oil type and kind of food being fried can be statistically described and used to develop a simple equation using the TPC and AV value as variables (y= 117 - 8 * AV - 3 * TPC) to find the point of disposal and to monitor the degradation process. The new criterion has been proven in the controlling of various industrial frying processes, restaurants and bakeries and kitchen frying. Practical applications: A simple equation of linear regression using AV and TPC as variables (y= 117 - 8 * AV - 3 * TPC) has been developed to monitor the level of degradation and to determine the point of disposal of used frying fats and oils much more reliable than using only one of the recommended parameters (TPC, AV or PTG). This criterion is independent of fat composition, food to be fried or frying process conditions and effectively helps to overcome the limitations of TPC and other major regulatory parameters related to the frying/baking industry. The good correlation of the results of the equation with the sensory quality of the fried food provides a powerful predictive tool for accurate calculation of the oil disposal point. This is useful since the quality of the fried food strongly depends on the quality of the frying oil that is absorbed by the food and becomes a major ingredient in the final product. This tool can easily be used to improve frying oil quality which finally improves the quality of the food to be fried. With continuous improvement this tool can become useful in reducing time and costs required for a human sensory panel.

Sterol dimers are the main oxidation products formed during sterols degradation at elevated temperatures. An investigation was carried out to decipher the structure of dimers differing in polarity, formed during β-sitosterol thermo-oxidation. The oxidation products were fractionated using silica gel into non-polar (NP), mid-polar (MP) and polar fractions (P). Oligomers were further separated by size-exclusion chromatography (SEC). Tentative chemical structures of non-polar, mid-polar and polar dimers were identified using Ag(+)/CIS-MS and APCI-MS procedures after on-line RP-HPLC separation. Further structures were verified by NMR and FT-IR spectroscopies.

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.

Novel antioxidants, derivatives of trolox, and selected phenolic acids have been prepared in good yields and fully characterized by (1)H NMR, (13)C NMR, and MS. Their antioxidant activities have been assessed by DPPH and ORAC assays, and during frying and accelerated storage tests. Novel phenolic compounds exhibited higher radical scavenging activities than both trolox and α-tocopherol. Trolox hydroxybenzoate showed a significantly higher protection than α-tocopherol under storage conditions. All new antioxidants performed better than α-tocopherol under frying conditions. Moreover, their outstanding thermal stability makes them more valuable than α-tocopherol for frying applications.

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.