Secondary Oxidation Compounds Research Articles

Integral oxidation Value used as a new oxidation indicator for evaluation of advanced stages of oxidative processes: Intox value

Oxidation of food lipids is one of the main causes of food spoilage. Oxidative processes of oxidisable substances, such as vegetable oils generate primary and secondary oxidation compounds. Peroxide Value and Anisidine Value are indicators of these compounds. TOTOV Value is an indicator that complements the interpretation of both results (2*PV + AV), but in advanced oxidative processes it does not usually fit the situation efficiently due to the decrease of PV. The aim of this research work was to develop an indicator that was efficiently adapted to advanced oxidative processes. Integral Oxidation Value (INTOX Value) calculated as PV + 2*AV, allowed for an improvement in the regression slopes, and the R2 fits went from low values in TOTOX Value (0.61–0.62) to acceptable values in INTOX Value (0.84–0.93). INTOX Value is a suitable indicator for advanced oxidation processes when the PV indicator decreases.

Use of mushrooms as antioxidants in a lipid oxidation model under indirect and direct oxidation tests: ethanolic extracts of Ganoderma resinaceum and Phlebopus bruchii.

Foods contain lipids that are easily susceptible to oxidation, which can modify their sensory properties. Although these compounds provide characteristic flavours and odours, there are also unwanted compounds, such as volatile secondary oxidation products, representing a recurring problem for both the industry and consumers. Synthetic antioxidants are often employed to prevent this but their chronic consumption can be detrimental to human health. The present study evaluates the antioxidant potential of ethanolic extracts from Ganoderma resinaceum and Phlebopus bruchii using an accelerated oxidation test. The composition profile of the extracts was investigated, identifying the presence of tryptophan, quinic acid, caffeic acid and 3,4-dihydroxyphenylglycol-phenolic acid. The antioxidant capacity of the extracts was compared with that of butylated hydroxytoluene (BHT) in sunflower oil that was oven-heated at 60 °C. Chemical (peroxide value, p-anisidine value and conjugated dienes) and volatile (2-octenal, 2-heptenal and 2,4-decadienal) indicators were measured over 28 days. The peroxide value decreased for both extracts at a similar level to that of BHT 0.02% w/w, and conjugate dienes decreased in the presence of G. resinaceum 0.1% w/w. Meanwhile, p-anisidine exhibited a slightly greater decrease for P. bruchii 0.1% w/w than for BHT. The sample with 0.1% w/w of extracts showed a reduction in volatile secondary oxidation compounds, indicating significant antioxidant activity. Based on these results, both extracts could be proposed as potential antioxidants in foods with a high lipid content. © 2024 Society of Chemical Industry.

Influence of storage temperature and natural antioxidants addition on chia oil nutraceutical blends shelf life

AbstractThis study focuses on the influence of storage temperature and addition of commercial natural antioxidant‐rich sources on the shelf life of chia oil (CO) nutraceutical blends. CO is a valuable product for consumers due to its high ω‐3 content, but its susceptibility to oxidation comprises challenges for its shelf life and quality. Thereby, different chia oil‐antioxidant blends were prepared and stored at 4°C and 25°C to evaluate alternative shelf‐life conditions. Commercial antioxidant‐rich sources containing astaxanthin (ASX), β‐carotene (BC) and vitamin E (VE) were added either alone or combined to CO. To monitor blends oxidative stability during storage, primary and secondary oxidation compounds were assessed weekly using peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) as indicators. Results showed that storage temperature played a significant role on oxidative stability of CO. When stored under refrigeration at 4°C, the oil exhibited low and stable oxidation indicators over time, regardless of the antioxidants used. However, at room temperature (25°C), the use of antioxidants and some particular combinations of them became crucial to prevent oil oxidative deterioration. Nutraceutical blends of CO/BC and CO/ASX were the best options to preserve CO from oxidation after 8 weeks storage at room temperature (PV < 2 meq O2/kg oil).Practical Applications: This work provides evidence on enhancing oxidative stability of chia oil through addition of natural antioxidants and proper storage. We focused primarily on designing blends from edible ingredients that are currently available in the market, with the aim of ensuring easy accessibility and affordability. Our findings offer valuable insights for the development of chia oil and antioxidant‐enriched blends, that could potentially serve as nutraceuticals or pharmacy‐compounded supplements to manage specific chronic inflammatory diseases. Our study highlights the importance of considering storage temperature and antioxidant selection to enhance shelf life and quality. These results have significant implications for the food industry, nutrition, and health, by providing valuable information for the creation of healthier and more sustainable food products. Furthermore, this work underscores the need for companies and retailers handling and storing vegetable oils with high omega‐3 content to adopt improved storage practices to ensure the quality and longevity of their products.

The prooxidant effect of natural antioxidants combination when co‐encapsulated to chia oil‐based nutraceutical edible powders: More is not always better

AbstractChia oil (CO) is the vegetable source with the highest ω − 3 polyunsaturated fatty acids (PUFAs) proportion known to date (61%–70%). Although this is favorable from a nutritional point of view, higher contents of ω − 3 PUFAs result in shorter shelf life and poorer oxidative stability. The objective of this work was to design edible oil powders of CO co‐encapsulated with commercial antioxidant‐rich sources—containing β‐carotene (BC), astaxanthin (ASX), and vitamin E (VE), either alone or combined (BC–VE and ASX–VE)—to prolong its oxidative stability. To carry out this, spray‐dried microcapsules were produced through oil‐in‐water double‐layered emulsions using whey proteins and pectin. Spray‐dried capsules were stored at 4 and 30°C, and weekly determinations of primary and secondary oxidation compounds were carried out, by measuring peroxide value (PV) and thiobarbituric reactive substances. CO microcapsules with just one commercial antioxidant‐rich source played a key role to keep oxidative indicators below recommended limits (PV < 15 meq kg−1 oil) when storing powders at 30°C, being ASX the best option, whereas there was no significant effect in oxidation when stored at 4°C. Nevertheless, when combining commercial antioxidant sources (BC–VE and ASX–VE), a marked prooxidant effect was observed, exceeding PV threshold at both temperatures after 2 months of storage.Practical Applications: Combination of chia oil and natural antioxidant commercial sources in edible powders constitutes a promising commodity to design potentially anti‐inflammatory nutritional interventions to prevent chronic noncommunicable diseases. This study contributes to show that mixing different antioxidants with chia oil might have a detrimental effect on oil oxidative stability during storage, so caution must be applied when formulating this type of functional ingredients as more is not always better. The goal of this contribution is that it was possible to obtain an easy‐to‐handle powder nutraceutical ingredient containing both chia oil and astaxanthin (using antioxidant concentrations that might have a significant effect on human health) that could be stored at 30°C up to 8 weeks, keeping oxidative indicators below the limits recommended by Codex Alimentarius (peroxide value <15 meq kg−1 oil).

Concentration of milk oxylipins after heat and homogenization treatments

Heat treatment and homogenization of milk are common processing steps intended to reduce microbial load for safe human consumption, and to avoid creaming, respectively. Although the effects of combined pasteurization and homogenization on free fatty acids (FFA) and lipid oxidation markers such as hydroperoxides, and thiobarbituric acid reactive species (TBARS) have been well characterized, their effects on primary oxidized fatty acids known as oxylipins have not yet been determined. This study aimed to determine the effects of two heat treatments: milk pasteurization [high-temperature short time, 72°C for 15 s (HTST)] and sterilization [ultra-high temperature, 135°C for 3 s (UHT)] with or without homogenization (10, 17 or 24 MPa) on FFA (%), primary (hydroperoxides and oxylipins) and secondary oxidation compounds (TBARS). Heat treatments alone significantly reduced most oxylipins compared with raw milk, but did not alter % FFA, hydroperoxide, and TBARS levels. The combination of UHT and homogenization at 24 MPa increased % FFA, hydroperoxide value, and some oxylipins, compared to raw milk and other treatments. Overall, the combination of heat treatment and homogenization significantly increased oxylipin formation compared with heat treatment alone.

Effect of post-milling process on the oxidation of the rice bran

The rancidity of rice bran is predominantly triggered by lipophilic enzyme activities. Bran stabilisation and defatting are the typical processes to inactivate the processes that cause rancidity. However, little is known about how this impacts the development of volatile compounds related to odour in the rice bran. The effects of the post-milling process on the development of secondary volatile oxidation compounds in the rice bran during storage were investigated. Based on the identified metabolites, there were three possible major pathways in the formation of off-odour and key aroma degradation of the stabilised rice bran during storage, including lipid oxidation, the Maillard reaction, and Strecker degradation. Butanal-2 methyl and furan compounds contributed to the cocoa, nutty, and malty aroma and were considered the important key aroma in the defatted stabilised bran. By contrast, butanal, hexanal, 2-hexenal, butanoic acid, hexanoic acid, pentanoic acid, and heptanoic acid were the discriminant volatile compounds in the non-defatted bran, and they were considered as the markers of rancidity of non-defatted stabilised rice. It can thus be suggested that the defatting process positively contributed to the low abundance of volatile oxidation products that are responsible for bran rancidity by slowing down the formation of lipid-derived oxidation products.

Influence of solvent-free extraction of fish oil from catfish (Clarias magur) heads using a Taguchi orthogonal array design: A qualitative and quantitative approach.

This study aimed to efficiently utilize catfish heads, enhancing the oil extraction process while improving the cost-effectiveness of fish byproduct management. The study employed the wet rendering method, a solvent-free approach, utilizing a two-factor Taguchi orthogonal array design to identify critical parameters for optimizing oil yield and ensuring high-quality oil attributes. The extraction temperature (80-120°C) and time (5-25 min) were chosen as variables in the wet rendering process. Range analysis identified the extraction time as a more significant (p < 0.05) factor for most parameters, including oil yield, oil recovery, acid value, free fatty acids, peroxide value, and thiobarbituric acid reactive substances. The extraction temperature was more significant (p < 0.05) for oil color. Consequently, the wet rendering method was optimized, resulting in an extraction temperature of 80°C and an extraction time of 25 min, yielding the highest oil yield. This optimized wet rendering process recovered 6.37 g/100 g of oil with an impressive 54.16% oil recovery rate, demonstrating comparable performance to traditional solvent extraction methods. Moreover, Fourier transfer infrared spectra analysis revealed distinct peaks associated with triacylglycerols and polyunsaturated fatty acids (PUFA). The oil recovered under optimized conditions contained higher levels of PUFA, including oleic acid (189.92 μg/g of oil), linoleic acid (169.92 μg/g of oil), eicosapentaenoic acid (17.41 μg/g of oil), and docosahexaenoic acid (20.82 μg/g of oil). Volatile compound analysis revealed lower levels of secondary oxidation compounds under optimized conditions. This optimized wet rendering method offers practical advantages in terms of cost-efficiency, sustainability, reduced environmental impact, and enhanced oil quality, making it an attractive option for the fish processing industries. Future research possibilities may include the purification of the catfish head oil and its application in the food and pharmaceutical industries.

Monitoring of the oxidation process of egg yolk phospholipids at frying temperature by nuclear magnetic resonance

Egg yolk phospholipids (EPLs) are sensitive to oxidation and can produce large quantities of volatile compounds. This study monitored the oxidation process of EPLs at frying temperature. The changes in the classes of EPLs, molar percentages of their fatty acyl groups and the concentrations of oxidation compounds under frying temperature were monitored by 31P nuclear magnetic resonance (NMR) and 1H NMR. Meanwhile, egg yolk triglycerides (ETGs) were used as controls. EPLs were mainly composed by phosphatidylcholine (76.74% ± 1.48%), phosphatidylethanolamine (17.97% ± 1.40%) and phosphatidylserine (1.26% ± 0.55%). EPLs, especially phosphatidylethanolamine, were degraded significantly during heating. The molar percentages of unsaturated acyl groups in EPLs were decreased, while the percentages of saturated plus modified acyl groups were increased during heating. EPLs produced large quantities of hydroperoxides and secondary oxidation compounds quickly. The results proved that EPLs were more sensitively to oxidation than ETGs during frying process, and EPLs could generate abundant of secondary oxidation compounds, especially 2,4-alkadienals, which demonstrated that EPLs are an ideal precursor of lipid-derived odorants.

Quality evaluation of different repeatedly heated vegetable oils for deep-frying of yam fries

Many studies have been conducted to evaluate the quality of repeatedly heated oils (RHO) used in deep-frying potato fries, but little is known about the quality of RHO used for deep-frying yam fries. Therefore, this study investigated the quality of RHO used for deep-frying yam fries, focusing on coconut oil (CNO), sunflower oil (SFO), and soybean oil (SBO). The oils’ quality was determined by changes in moisture content, acid value (AV), free fatty acid (FFA), iodine value (IV), peroxide value (PV), and total polar compounds (TPC). The oils’ degradation and the presence of primary and secondary oxidation products were evaluated with thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR), respectively. The TGA curves indicated that the thermal stability of RHO followed the trend: RSFO (217 °C) > RSBO (187 °C) > RCNO (158 °C). RHO recorded a sharp increase in AV, FFA, PV, and TPC. The presence of secondary oxidation compounds was registered at a peak intensity of around 1742 cm−1 using the FTIR technique. A significant decrease (p < 0.05) in IV, PUFAs, β-carotenes, and color content were registered, rendering RHO unsuitable for deep-frying of yam fries. Finally, the RHO quality decreased in the following order: RSFO > RSBO > RCNO, implying that oils with a high degree of saturation are less susceptible to thermal changes during deep-frying.

Antimicrobial and antioxidant effect of lyophilized Fucus spiralis addition on gelatin film during refrigerated storage of mackerel

Lyophilized alga Fucus spiralis powder was incorporated into a gelatin-based film and employed as a packaging system for mackerel ( Scomber scombrus ) muscle portions throughout a 9-day refrigerated storage period at 4 °C. In global terms, a progressive loss of quality could be observed in fish muscle with increasing storage time. Comparisons between batches allowed us to conclude an inhibitory effect of F. spiralis -containing films on microbial activity (assessment of aerobes, psychrotrophs, and proteolytic bacteria) and on lipid hydrolysis (as determined by free fatty acid formation) in mackerel muscle. The presence of the lyophilized macroalga in the packaging film also led to a higher retention of primary (peroxides) and secondary (thiobarbituric acid reactive substances) lipid oxidation compounds, while the formation of fluorescent compounds (interaction compounds between lipid oxidation compounds and nucleophilic molecules present in the fish muscle) decreased. Both antimicrobial and antioxidant effects were more intense when the concentration of alga in the packaging film was increased. The preservative effect resulting from the presence of F. spiralis in gelatin-based films demonstrates the potential employment of such bioactive films to improve the retention of fish quality and enhance its commercial value. • Lyophilized Fucus spiralis was incorporated into a gelatin packaging film. • F. spiralis in the packaging film inhibited free fatty acid formation in mackerel. • F. spiralis inhibited aerobes, psychrotrophs, and proteolytic bacteria in fish muscle. • F. spiralis in the packaging film inhibited fluorescent compound formation. • Superior retention of primary and secondary lipid oxidation compounds was observed.

Comparative Study of Astaxanthin, Cholesterol, Fatty Acid Profiles, and Quality Indices Between Shrimp Oil Extracted From Hepatopancreas and Cephalothorax.

Shrimp oil from two different portions of Pacific white shrimp including cephalothorax and hepatopancreas was extracted using the mixture of hexane/isopropanol (1:1). The extracted oils from the cephalothorax (CPO) and hepatopancreas (HPO) were characterized for astaxanthin content, cholesterol levels, and fatty acid profiles. Nutrition indices of CPO and HPO were also compared. CPO had lower extraction yield (3.2 ± 0.1%, wet weight basis) than HPO (11.1 ± 0.5%, wet weight basis). High-performance liquid chromatography results indicated that the astaxanthin content in HPO was higher, compared to that of CPO. Nevertheless, the cholesterol level in HPO was 70% lower than that of CPO. Fatty acid profiles of HPO and CPO demonstrated that the polyunsaturated fatty acid (PUFA) content in HPO was higher than that of CPO. The amount of docosahexaenoic acid in the former was ~2 times higher than that of the latter. HPO contained 42.76 ± 0.36% PUFA, whereas PUFA content of CPO was 35.27 ± 0.19%. On the other hand, saturated fatty acids (SFA) were more pronounced in CPO (38.44 ± 0.26%) than HPO (30.82 ± 0.55%). Based on nutrition indices, namely, atherogenicity index, thrombogenicity index, hypocholesterolemic/hypercholesterolemic (h/H) ratio, and PUFA/SFA ratio, HPO possessed higher health benefit than CPO. The oxidation status of CPO and HPO measured in terms of peroxide value, thiobarbituric acid reactive substances, anisidine value, and conjugated dienes indicated that higher primary oxidation products were present in CPO, whereas HPO exhibited more secondary oxidation compounds. Fourier transform infrared spectra further substantiated the presence of oxidation products in CPO and HPO. Liquid chromatography-mass spectrometry identification showed the enhanced levels of phospholipids and glycolipids in the ethanolic fraction of CPO. Overall, HPO with a higher yield was more beneficial in terms of health benefits than CPO.

Formation of Secondary and Tertiary Volatile Compounds Resulting from the Lipid Oxidation of Rapeseed Oil

The lipid oxidation of fats and oils leads to volatile organic compounds, having a decisive influence on the sensory quality of foods. To understand formation and degradation pathways and to evaluate the suitability of lipid-derived aldehydes as marker substances for the oxidative status of foods, the formation of secondary and tertiary lipid oxidation compounds was investigated with gas chromatography in rapeseed oils. After 120 min, up to 65 compounds were detected. In addition to secondary degradation products, tertiary products such as alkyl furans, ketones, and aldol condensation products were also found. The comparison of rapeseed oils, differing in their initial peroxide values, showed that the formation rate of secondary compounds was higher in pre-damaged oils. Simultaneously, a faster degradation, especially of unsaturated aldehydes, was observed. Consequently, the formation of tertiary products (e.g., alkyl furans, aldol adducts) from well-known lipid oxidation products (i.e., propanal, hexanal, 2-hexenal, and 2-nonenal) was investigated in model systems. The experiments showed that these compounds form the new substances in subsequent reactions, especially, when other compounds such as phospholipids are present. Hexanal and propanal are suitable as marker compounds in the early phase of lipid oxidation, but at an advanced stage they are subject to aldol condensation. Consequently, the detection of tertiary degradation products needs to be considered in advanced lipid oxidation.

Oxidative Quality of Acid Oils and Fatty Acid Distillates Used in Animal Feeding.

Simple SummaryFeed producers and farmers seek alternative and economical fat ingredients to supply animals with energy and beneficial components, such as natural antioxidants. Some byproducts from the edible oil refining industry, such as acid oils (AO) and fatty acid distillates (FAD), fulfil these requirements, but differences in the animal performance have been reported as their main drawback, which might be due to their high variable composition, including their oxidation status. Therefore, the valorization of these byproducts as feed ingredients requires ensuring standardized products with adequate quality in terms of oxidation parameters. In this study, 92 AO and FAD were characterized, finding a huge variability in their oxidation status and stability. They all showed low primary oxidation values (peroxide values). The content of secondary oxidation compounds was higher in FAD (which are released from physical refining processes) than in AO (which originate from chemical refining), while polymeric compounds were higher in the latter. The fatty acid and tocol compositions that were related with the botanical origin influenced their oxidative stability. Thus, in the quality control of these products, apart from the compositional parameters, it is recommended to include the evaluation of the oxidation status, both by primary and secondary oxidation parameters.Acid oils (AO) and fatty acid distillates (FAD) are byproducts from chemical and physical refining of edible oils and fats, respectively. Their high energy value makes their upcycling interesting as alternatives to conventional fats in animal feeding. The objective of this study is to characterize their oxidative quality and to provide recommendations about their evaluation for animal feeding purposes. The oxidation status (peroxide value (PV), p-Anisidine value (p-AnV), % polymeric compounds (POL)), the oxidative stability (induction time by the Rancimat at 120 °C (IT)), the fatty acid composition (FA), and tocopherol and tocotrienol content of 92 AO and FAD samples from the Spanish market were analyzed. Both AO and FAD showed low PV (0.8 and 1 meq O2/kg); however, p-AnV was higher in FAD (36.4 vs. 16.4 in AO) and POL was higher in AO (2.5% vs. not detected in FAD) as a consequence of the type of refining process. The botanical origin of AO and FAD influenced FA and tocol composition, and they influenced IT. A high variability was observed for most analyzed parameters, reinforcing the need for standardizing AO and FAD to obtain reliable feed ingredients and to include primary and secondary oxidative parameters within their quality control.

The Extended Oxidative and Sensory Stability of Traditional Dairy-Based Oil with Steam-Distilled Essential Oils Extracted from the Bioactive-Rich Leaves of Ziziphora tenuior, Ferulago angulata, and Bunium persicum

The oxidation rate and overall sensory acceptability of Iranian animal oil (IAO) during storage were evaluated after adding the bioactive essential oils extracted from medicinal herbs of Ziziphora tenuior, Ferulago angulata, and Bunium persicum. Results showed that the most dominant chemical constituents in Z. tenuior, F. angulata, and B. persicum essential oils were pulegone (12.77%), ferulagon (14.97%), and (+)-trans-carveol (57.70%), respectively. IAO contained more saturated fatty acids (67.43%, mainly palmitic and myristic acids) than unsaturated (32.27%, mostly oleic acid) ones. B. persicum essential oil compared to the other two oils significantly had more total flavonoid (1.08 mg quercetin equivalent/g), phenolic (123.2 mg GAE/g), carotenoid (591.31 mg/kg), and chlorophyll (24.32 mg/kg) contents. A significant dose-dependent increase in the overall sensory acceptability of IAO was found by increasing the concentration of B. persicum essential oil. Similar to tertiary butyl hydroquinone, the oil blend of IAO+10% B. persicum essential oil obtained the maximum overall sensory acceptability scores during 28 d cold storage due to the remarkable in vitro DPPH inhibition (83.45%) and ferric-reducing power (0.754 at Å700nm). A much slower formation rate in primary and secondary oxidation compounds in IAO rich in B. persicum essential oil during the storage was associated with the overall sensory acceptability data ( p &lt; 0.01 , r = 0.951). Thus, this bioactive additive as a bio-preservative may well stabilize crude oils and emulsions.

In Silico and In Vitro Evaluation of the Antimicrobial and Antioxidant Potential of Mentha × smithiana R. GRAHAM Essential Oil from Western Romania.

This study was conducted to identify the volatile compounds of Mentha × smithiana essential oil (MSEO) and evaluate its antioxidant and antibacterial potential. The essential oil (EO) content was assessed by gas chromatography–mass spectrometry (GC-MS). Carvone (55.71%), limonene (18.83%), trans-carveol (3.54%), cis-carveol (2.72%), beta-bourbonene (1.94%), and caryophyllene oxide (1.59%) were the main identified compounds. The MSEO displayed broad-spectrum antibacterial effects and was also found to be the most effective antifungal agent against Candida albicans and Candida parapsilosis. The antioxidant activity of MSEO was tested against cold-pressed sunflower oil by peroxide, thiobarbituric acid, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), and β-carotene/linoleic acid bleaching methods. The EO showed strong antioxidant effects as reflected by IC50 values of 0.83 ± 0.01 mg/mL and relative antioxidative activity of 87.32 ± 0.03% in DPPH and β-carotene/linoleic acid bleaching assays, respectively. Moreover, in the first 8 days of the incubation period, the inhibition of primary and secondary oxidation compounds induced by the MSEO (0.3 mg/mL) was significantly stronger (p < 0.05) than that of butylated hydroxyanisole. In silico molecular docking studies were conducted to highlight the underlying antimicrobial mechanism as well as the in vitro antioxidant potential. Recorded data showed that the antimicrobial activity of MSEO compounds could be exerted through the D-Alanine-d-alanine ligase (DDl) inhibition and may be attributed to a cumulative effect. The most active compounds are minor components of the MSEO. Docking results also revealed that several mint EO components could exert their in vitro antioxidant activity by employing xanthine oxidase inhibition. Consequently, MSEO could be a new natural source of antioxidants and antiseptics, with potential applications in the food and pharmaceutical industries as an alternative to the utilization of synthetic additives.

Effects of grape pomace flour on quality parameters of salmon burger

By-products from the juice industry contain a large proportion of high-value compounds, such as polyphenols, that can be applied as natural antioxidants in foods. The effects of grape pomace flour (GPF) were assessed on oxidative stability, physicochemical, and sensory characteristics of frozen salmon burgers. Two batches of burgers were formulated with 1% and 2% GPF. For comparison purposes, a negative control (0% GPF) and a burger added with 0.01% BHT were formulated. The incorporation of GPF into salmon burger altered the color and appearance, but did not affect the odor. TBARS was significantly inhibited by the incorporation of GPF, in which BHT showed the highest inhibitory effect. Additionally, the GPF showed no cytotoxicity in relation to mouse fibroblast cells. These results suggest that GPF is one potential inhibitor of secondary lipid oxidation compounds in salmon burgers, thus indicating that it can be applied in food applications to replace synthetic antioxidants. Practical applications By-products from grape juice processing contain high levels of polyphenols and dietary fibers that are discarded without taking advantage of the bioactive. The use of grape pomace flour as a natural antioxidant for the development of new products represents an alternative for the fish industries to meet consumers’ expectations for healthier foods.

Nanocomposite bilayers based on poly(vinyl alcohol) and chitosan functionalized with gallic acid

The development of active bilayer systems is a novel strategy for the application of active packaging to maintain or prolong the shelf‐life of food products. A bilayer system was assembled in situ into a thermocompression unit through a two-step procedure. One of the layers was obtained by a casting process and consisted of a chitosan-based nanocomposite functionalized with gallic acid (GA); the other was shaped by the spreading of polyvinyl alcohol solution on the nanocomposite. Then, a stage of thermocompression formed the bilayer system. In this way, a feasible material with water vapor and oxygen barrier as well as UV barrier properties due to the presence of GA was designed by a thermocompression process which can be industrially scaled representing a technological progress. The formation of the bilayers was corroborated by SEM allowing discerning between both, the PVA layer and the nanocomposite layer. On the other hand, the corroboration of interactions between the layers of the system was carried out through ATR-FTIR and DSC analysis. The system was used as packaging of a food susceptible to undergo oxidation such as walnut flour, generating a delay in the formation of hydroperoxides and secondary oxidation compounds compared with a synthetic container. These results indicated that bilayer materials can be useful for the conservation of this type of foods.

Enrichment of Sunflower Oil with γ‐Tocopherol. Study by 1H NMR of Its Effect Under Accelerated Storage Conditions

The effect of the enrichment of sunflower oil with γ‐tocopherol on the evolution of its oxidation is the subject of this study. Sunflower oil and samples of this oil enriched with different γ‐tocopherol concentrations are submitted to accelerated storage conditions and their evolution, until total polymerization is monitored by 1H NMR spectroscopy. The concentrations of linoleic acyl groups, of primary and of a great number of secondary oxidation compounds are determined throughout the process. These concentrations, and the times at which the main changes in them occur are analyzed to elucidate if they are valid markers of the global effect of γ‐tocopherol enrichment. It is proved for the first time that certain comparisons between concentrations of some of the compounds formed in oxidation can lead to erroneous conclusions about the effect of this enrichment. It is shown that, during a first short period of time under accelerated storage conditions, the higher the concentration of γ‐tocopherol the faster the degradation of linoleic acyl groups and the higher the concentration of hydroperoxides; after this first period this relationship is more complex. Generally, the higher the γ‐tocopherol concentration the slower the degradation of the oil, except in the first period.Practical Applications: This study provides very valuable information about the effect caused by enrichment with γ‐tocopherol on sunflower oil oxidative stability and oxidation across a very broad range of concentrations. In addition, the amount of information obtained can be of great importance from several points of view because the oxidation process has been monitored globally. This may be of interest not only to researchers involved in the analysis of oxidation mechanisms but also to those in the field of technology and edible oil legislation, and even to those worried about edible oil safety and its effect on nutrition and health. Another important feature of this study, from the practical point of view, is the methodology used because it does not involve the chemical modification of the sample and the same 1H NMR spectrum is able to provide information about all the above‐mentioned aspects.Sunflower oil enriched with different levels of γ‐tocopherol. Concentrations of primary and secondary oxidation compounds after 4 and 9 days, respectively, under accelerated storage conditions.

The potential of lysine to extend the shelf life of soybean oil evidenced by 1H Nuclear Magnetic Resonance

The effect of 1% and 2% proportions of L-lysine on the oxidation process of soybean oil, performed at 70 °C under stirring conditions, has been studied by 1H Nuclear Magnetic Resonance. This technique allows one to monitor the generation and further evolution of a wide variety of oxidation products (hydroperoxides, epoxides, aldehydes, keto-dienes and hydroxy-derivatives), providing a comprehensive view of the oxidation process. The addition of lysine considerably delays the degradation of the oil acyl groups and the generation of both primary and secondary oxidation compounds, while preserving the oil content of γ-tocopherol for longer, especially at the highest enrichment level. A diminution in the maximum concentration reached by some types of secondary oxidation products is also observed in the lysine-enriched samples. This is particularly noticeable for aldehydes, whose concentration is markedly reduced, above all that of the toxic oxygenated α,β-unsaturated ones, probably due to their reaction with lysine. Therefore, the ability of lysine to extend the shelf life of soybean oil is proved in this work, as well as its feasibility as a potential antioxidant for use in lipidic foods. These findings could also contribute to a better understanding of the antioxidant effect of proteins.

The effect of glazing based on saponin-free quinoa (Chenopodium quinoa) extract on the lipid quality of frozen fatty fish

This study focussed on the rancidity stability of frozen fatty fish. Its basic objective was to investigate the effect of a glazing system including a saponin-free quinoa (Chenopodium quinoa) extract during the frozen storage of Atlantic mackerel (Scomber scombrus). For it, two different concentrations of 80% aq. (v/v) ethanol quinoa extracts (0.45 and 1.36 g lyophilised quinoa L−1 solution, respectively) were tested and compared with two control treatments (water glazing and non-glazing conditions). Chemical and sensory changes were monitored for a 8-month frozen storage. An inhibitory effect (p < 0.05) of the glazing system including the most concentrated saponin-free quinoa extract was observed on the lipid hydrolysis (free fatty acid formation) evolution and on the formation of secondary (thiobarbituric acid reactive substances) and tertiary (fluorescent compounds) lipid oxidation compounds. A sensory quality enhancement and shelf life increase was obtained in fish submitted to glazing conditions including the most concentrated quinoa extract in agreement to raw (gills and muscle odour) and cooked (muscle odour) descriptors. A novel quinoa-glazing system is proposed, this avoiding the inconveniences of the saponin compounds presence.