Development of a method predicting the oxidative stability of edible oils using 2,2-diphenyl-1-picrylhydrazyl (DPPH)

The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to predict the oxidative stability of edible oils. The principle of DPPH method is to measure the free radicals generated from oxidized oils directly. The absorbance of DPPH from oils before thermal oxidation decreased proportionally to the concentration of free radical scavenging compounds such as butylated hydroxytoluene (BHT). Oxidized oils with high polyunsaturated fatty acid (PUFA) contents showed high changes in DPPH absorbance or free radical formation rates than those with low PUFA. Oxidized oils with high BHT content were more stable and showed slower pattern change of DPPH absorbance from positive to negative slopes than those with low BHT content. Oxidative stability of oils could be predicted considering the initial values of DPPH absorbance, the free radical formation rates, and the oxidation period for pattern changes. The results from DPPH method on the oxidative stability of vegetable oils agreed with conventional methods such as p-anisidine value (p-AV), conjugated dienoic acids (CDA), or total polar matter (TPM).     

ω‐3 in meat products: benefits and effects on lipid oxidative stability

Although ω‐3 intake has been associated with numerous health benefits, its addition to certain food matrices, and in particular meat products, may involve various technological barriers influencing the final quality of the products. Lipid oxidation must be highlighted due to the modification of both the sensory characteristics and the shelf‐life of meat products. In order to reduce the impact of chemical changes and promote oxidative stability, the use of natural antioxidants has gained ground owing to the health and safety advantages linked to its effectiveness at reducing lipid oxidation. Many natural compounds have also been successfully tested in animal feed, in order to protect the raw meat materials and reduce the risk of lipid oxidation in processed products. This review aims to address the challenges and advantages of the incorporation of ω‐3 fatty acids in raw meat materials and processed meat products, and to describe the use of different compounds to enhance lipid oxidative stability. © 2015 Society of Chemical Industry     

Changes in chemical quality indices during long‐term storage of palm‐olein oil under heated storage and transport‐type conditions

Six quality indices, namely free fatty acids (FFA), peroxide value (PV), anisidine value (AV), oxidative stability index (OSI), total tocopherols and headspace volatiles (hexanal, t‐2‐hexenal and t,t‐2,4‐decadienal), were evaluated in a long‐term storage trial of 52 weeks at 50 °C of palm‐olein, a monounsaturated oil. Three concentrations of copper (0.035, 0.17 and 0.69 mg kg^?1) were added. FFA values for all the sample treatments increased slightly over the storage period but remained within acceptable limits. PV of the copper‐containing samples declined initially and then remained stable up to week 40, after which it increased slightly for the 0.035 and 0.17 mg kg^?1 samples. However, PV of the control (no added copper) increased steadily to above the acceptable limit. AV of the copper‐containing samples increased much more than that of the control. OSI and total tocopherol values of the copper‐containing samples were markedly lower than those of the control. t‐2‐Hexenal did not increase during the storage period, whereas hexanal increased in the copper‐containing samples but at a slower rate than in the control. Conversely, the copper‐containing samples had high levels of t,t‐2,4‐decadienal but the control had none. AV, OSI and total tocopherols are the most valuable quality indices for assessing monounsaturated oil quality, whereas FFA, PV and headspace volatiles can be misleading. Copyright © 2003 Society of Chemical Industry     

Importance of instrumental and sensory analysis in the assessment of oxidative deterioration of omega‐3 long‐chain polyunsaturated fatty acid‐rich foods

Omega‐3 long‐chain polyunsaturated fatty acids (LC PUFA) positively influence human health. Their main dietary source is fish, especially fish oil. Owing to low fish consumption in many Western countries the average intake of omega‐3 LC PUFA is below the recommended level. This raises interest in diet supplementation and food enrichment with fish oil. However, due to a high degree of unsaturation fish oil is extremely susceptible to oxidation. Oxidation of fish oil increases when added to food products, which may be enhanced by some antioxidants, under certain conditions. For quality control of omega‐3 LC PUFA‐containing foods adequate and combined methods of oxidation assessment should be used, beginning from the raw material and continuing during processing, storage and distribution. To achieve this goal correlation of instrumental and sensory methods with multivariate data analysis may give the best results. In this paper problems of oxidation of fish oil and fish oil‐containing foods, as well as methods for its assessment, are reviewed. Copyright © 2006 Society of Chemical Industry     

Effect of long‐term dietary administration of oregano and rosemary on the antioxidant status of rat serum,liver, kidney and heart after carbon tetrachloride‐induced oxidative stress

BACKGROUND: This study was performed on female Wistar rats allocated to eight groups of six animals each. Groups 1 and 2 were fed the basal diet, groups 3 and 4 were fed the basal diet supplemented with ground oregano at 20 g kg^?1 level, groups 5 and 6 were fed the basal diet supplemented with ground rosemary at 20 g kg^?1 level, while groups 7 and 8 were fed the basal diet supplemented with both oregano and rosemary, each at 20 g kg^?1 level. Following 6 weeks feeding, groups 2, 4, 6 and 8 were injected with CCl₄ at 1 mL kg^?1 body weight, and 6 h thereafter all animals were sacrificed. RESULTS: Administration of CCl₄ to the control rats enhanced (P < 0.05) aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) activities, decreased cholesterol and triglycerides content in serum, increased (P < 0.05) lipid peroxidation and decreased (P < 0.05) the ABTS radical cation, the hydroxyl anion radical, the superoxide anion radical, and the hydrogen peroxide scavenging activities in all tested tissues, as compared to the control. Feeding oregano, rosemary or both before CCl₄ treatment resulted in decline (P < 0.05) of the increase in AST, ALT and ALP activities, increase (P < 0.05) of cholesterol and triglycerides in serum, decrease (P < 0.05) of lipid peroxidation, and increase (P < 0.05) of the ABTS radical cation, hydroxyl anion radical, superoxide anion radical and hydrogen peroxide scavenging activity. CONCLUSION: The results of this study suggest that long‐term dietary administration of oregano and rosemary has the potential to quench free radicals and alleviate CCl₄‐induced oxidative stress in rats. Copyright © 2009 Society of Chemical Industry     

Change in α‐tocopherol contents,lipid oxidation and fatty acid profile in eggs enriched with linolenic acid or very long‐chain ω3 polyunsaturated fatty acids after different processing methods

The influences of dietary supplementation with α‐tocopheryl acetate (α‐TA) and of processing (by hard‐boiling and scrambling) of eggs enriched with ω3 fatty acids, either very long‐chain ω3 polyunsaturated fatty acids (VLC ω3 PUFAs) or linolenic acid (LNA), on fatty acid composition, α‐tocopherol content and lipid oxidation (thiobarbituric acid (TBA) values) were studied. Four dietary treatments were formulated from a basal diet containing 40 g kg^?1 linseed oil (LO) or fish oil (FO) combined with either 0 or 100 mg α‐TA kg^?1 of feed. Eggs from LO treatments were enriched with LNA and those from FO treatments were rich in VLC ω3 PUFAs. Neither processing nor dietary supplementation with α‐TA modified greatly the fatty acid profile of eggs. Dietary supplementation with α‐TA increased the α‐tocopherol content of eggs (187.2 versus 407.9 µg g^?1 dry matter). Eggs from FO treatments showed lower α‐tocopherol content than those from LO treatments (273.5 versus 321.6 µg g^?1 dry matter), and processing of eggs enriched with VLC ω3 PUFA reduced the α‐tocopherol content by a significant 16%. Moreover, processing of eggs increased lipid oxidation two‐ to nine‐fold. Oxidation levels of hard‐boiled eggs were 30.4% higher than those of scrambled eggs. TBA values in hard‐boiled and scrambled eggs were significantly reduced when 100 mg α‐TA kg^?1 of feed supplemented the diet only in those eggs enriched with VLC ω3 PUFA (from FO treatments). Copyright © 2003 Society of Chemical Industry