Increase In Peroxide Value Research Articles

Comparison of meat quality characteristics and oxidative stability between conventional and free-range chickens

The aim of this research was to evaluate quality traits and oxidative stability of meat products from free-range (FR) and conventionally (C) raised chickens as they actually reach consumers in the Italian retail market. Free-range female and male chickens (n = 1,500 + 1,500), medium growing ISA strain, were raised under commercial conditions for 56 (1.8 kg of live weight) and 70 d (3.1 kg of live weight), respectively; C female and male birds (n = 5,000 + 5,000) were a fast growing hybrid (Ross 708) and were separately raised for 39 (1.9 kg of live weight) and 50 d (3.1 kg of live weight), respectively. A total of 96 chickens (equally divided by production system and sex) were slaughtered in 2 separate sessions to obtain the main 2 commercial categories (rotisserie and cut-up, respectively). After slaughtering, 12 carcasses of each treatment group were randomly selected and used to assess quality properties, chemical composition, and oxidation stability of breast and leg meat. The C birds had dramatic higher carcass and breast meat yield, whereas FR had higher wing and leg yields. The FR birds exhibited higher water holding capacity in both breast and leg meat. Although shear force did not differ in breast meat, legs from FR birds were tougher. Fatty acid composition of FR breast and thigh meat of both categories were characterized by a higher polyunsaturated fatty acid n-6-/n-3 ratio. In general, a low lipid oxidation level (peroxide value < 1.3 mEq O2/kg of lipid and TBA reactive substances < 0.2 mg malondialdehyde/kg of sample) was found in breast and legs, regardless of the commercial category. However, the C system significantly increased peroxide value in rotisserie thigh meat, whereas FR led to a significantly higher TBA reactive substances in breast meat. Our results demonstrated that free range can modify the properties of chicken meat and also highlighted the importance of the bird genetic background to select nutritional strategies to improve meat quality traits and oxidative stability in poultry.

Oxidative stability of lipids from hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) as affected by essential oils incorporation

Oxidative stability of lipids from hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) added with different essential oils at 200 ppm during 10 days of storage was studied. With increasing storage time, the progressive formation of hydroperoxide was found in all samples as evidenced by the increases in peroxide values (PV) (p&lt;0.05). Amongst all essential oils tested, lemon essential oil exhibited the highest preventive effect against oxidation, followed by plai and basil essential oils, respectively. The increases in thiobarbituric acid reactive substances (TBARS) and ρ‐anisidine value (AnV) of lipids were noticeable when storage time increased (p&lt;0.05). The increases in TBARS and AnV were retarded in the presence of essential oils. Nevertheless, the effectiveness for prevention of lipid oxidation of all three essential oils was slightly lower than α‐tocopherol when used at the same level. The formation of volatile compounds and rancid odour of samples were lowered when being incorporated with essential oils. Based on sensory evaluation, lipid containing lemon essential oil had a similar rancid odour to that added with α‐tocopherol. Thus, essential oils could be used as natural antioxidants to retard lipid oxidation and rancidity of lipids from hepatopancreas during extended storage.Practical applications: Shrimp hepatopancreas, a byproduct from shrimp processing industries, is an important source of lipids and astaxanthins, which are susceptible to oxidation. Their changes are associated with development of off‐odour and loss of nutritive value. Therefore, the uses of natural antioxidants, especially essential oils, can be a potential means to retard lipid oxidation and rancidity of shrimp oil during extended storage.Essential oils could be used as natural antioxidants to retard lipid oxidation and rancidity of lipids from hepatopancreas during extended storage.

Evaluating the potential of natural curcumin for oxidative stability of soybean oil

The active substance of turmeric rhizome (curcumin) was extracted and identified with TLC and NMR. To evaluate the antioxidant efficiency of different concentrations of curcumin (120, 160 and 200 ppm) compared with tert-butylhydroquinone (TBHQ) (120 ppm) and α-tocopherol (200 ppm) at two different temperatures (25°C and 55°C) under dark and light conditions during 90 days, the soybean oil with no added antioxidant was used as a food model, and its fatty acids profile was determined by GC. Results indicated that increasing concentration of curcumin leads to significantly decreased oxidation rates. The soybean oil containing curcumin at 25°C in darkness with the lowest rate of increased peroxide value indicated the same antioxidant activity with α-tocopherol and TBHQ. Moreover, the results of acid value and iodine value indicated that samples with curcumin were more effective in preventing oxidation at both temperatures compared with control. However, light did not have any significant effect.

The Study of Stability of Processing Grease Storage Temperature on Soybean

This paper studied the soybean under different temperature storage processing stability of greaseComparison of the moisture content, oil acid value and peroxide value under - 10 °C 0 °C and room temperature storage stored two years in soybean production fat The results show that,The higher the temperature the lower stability of greaseThe higher the temperature, the lower stability of moisture contentUnder - 10 °C, water content change is only 0.04%. at Room temperature the moisture content changes 0.11%The higher the temperature, the soybean processing oil acid value, peroxide value, the greater the increaseunder - 10 °CAcid value increased by 0.07KOH/(mg/g), under room temperature the acid value increases 0.97 KOH/(mg/g)Under - 10 °C peroxide value change tendency for 0.6 mmol/kg, room temperature peroxide value change tendency for 3.9 mmol/kgTherefore, low temperature could delay the deterioration of quality of soybean, and further improve the variation of water content, and delayed the acid value and peroxide value increase.

Effect of Frying Time and Temperature on the Functional Properties of Carrot Pomace, Pulse Powder and Rice Flour–Based Extrudates

Abstract The extrudates prepared under the optimized conditions of flour proportion (rice flour, pulse powder and carrot pomace), moisture content, screw speed and die temperature, were fried at temperatures of 170, 180, 190 and 200°C and for a time of 5, 10 and 15 s. Based on sensory characteristics, the selected product was stored for a period of 6 months in metalized polypropylene and evaluated for free fatty acid, peroxide value, hardness, crispiness, colour and beta carotene. The increase in colour L-values, b-values, oil absorption and decrease in colour a-values in carrot pomace–based rice extrudates was observed with the increase in frying temperature and time. The product obtained at 180°C for 15 s was rated better. The decrease in free fatty acid, colour L-values, b-values, crispiness and beta carotene and increase in peroxide value, hardness and colour a-values in carrot pomace–based rice extrudates was observed with the increase in storage period. However, the quantitative change in attributes suggested the acceptability of the product even after the storage of 6 month.

Effect of processing on the quality, composition and antioxidant properties of Terminalia catappa (Indian almond) seed oil

This study was aimed at extracting and purifying T. catappa seed oil with a view to investigating the effect of processing on the composition and antioxidant activity of the oil. Oil was extracted from the dried and roasted T. catappa seed and subjected to degumming and bleaching. The different processed oils were analysed for their fatty acid, phytosterols, and fat soluble vitamins composition. Antioxidant properties of the oils were also determined by measuring the Diphenylpicrylhydrazyl (DPPH) radical scavenging activity and inhibition of heat induced peroxidation. Roasting and processing caused a reduction in acid value, increased peroxide value, but had no effect on the iodine and saponification values of T. catappa oil. Palmitic acid was the most abundant saturated fatty acid (42.466%) while oleic acid was the most abundant unsaturated fatty acid (23.445%). Roasting significantly reduced fatty acid concentration of the oil, and bleaching of both unroasted and roasted oils increased the concentration of fatty acids except linoleic acid. Gamma-sitosterol and Betasitosterol were present in appreciable amounts only in the crude oils. Roasting increased Vitamins A and D concentrations but drastically reduced that of vitamin E. Degumming had no effect on the fat soluble vitamins of T. catappa oil, but bleaching significantly reduced the concentrations of all the vitamins. The DPPH radical scavenging activity of the seed oil was between 26.93 ± 15.42% and 65.47 ± 31.59%. Refining increased the free radical scavenging activity of the unroasted oil, but did not affect the antioxidant activity of roasted oil. The capacity of the oil in preventing heat induced peroxidation was comparable to that of Butylated hydroxytoluene (BHT). Processing of the oil significantly increased its antioxidant activity. Loss of vitamin E did not affect the antioxidant activity of the oil. Thus, suggesting the presence of a heat stable antioxidant in the oil. This study indicated T. catappa seed oil to be potential pharmaceutical oil with good antioxidant characteristics

Shelf-life of isolated phorbol esters from Jatropha curcas oil

The application of bio-control agents in agriculture is gaining tremendous importance. Plants represent a rich source of phytochemicals for bio-pesticides as well as raw material for agro-industries. Phorbol esters (PEs), a potent group of phytochemicals can be obtained as a by-product from Jatropha biodiesel industry. This PEs could be easily extracted from Jatropha curcas oil and used in bio-control agent formulations. In our study, long-term stability of methanol extracted phorbol esters enriched fraction (PEEF) was evaluated at different temperatures (room temperature (RT, 22–23°C), 4°C and −80°C; under dark) for >2 years. After day-132, 50% degradation of PEs in PEEF was observed at RT; while PEs was reduced only by 8% and 4% at 4°C and −80°C respectively. The snail bioassay conducted at regular intervals revealed that the PEEF lost biological activity more rapidly at RT, becoming ineffective after 260 days; while at 4°C and −80°C, only 28% and 33% of bioactivity was lost after 870 days. The degradation of PEs was presumed to be due to auto-oxidation. The auto-oxidation of PEEF was reflected with the changes in fatty acid composition, increase in peroxide value and decrease in free radical scavenging activity. Inclusion of antioxidants as additives increased the protection of PEs present in PEEF against degradation. In conclusion, the PEs present in PEEF are susceptible to oxidation and addition of antioxidant is required to increase their shelf life. It is recommended to store PEEF at cold storage facilities (≤4°C). If cold storage facilities are not available, then it is advisable to add stabilizers (0.09–0.13mg/g PEs) before storing PEEF at room temperature.

Effect of temperature on oxidation kinetics of walnut and grape seed oil

The effects of temperature on the oxidation of walnut oil (WO) and grape seed oil (GSO) were investigated. Both oils were stored at 25, 40, 60, and 80°C for 60, 30, 12, and 6 day, respectively. Degree of oxidation was measured in terms of peroxide value (POV), conjugated dienoic acid (CDA) value, and p-anisidine value (p-AV). The rates of increase in POV, CDA, and p-AV in both oils were strongly dependent on storage temperature. The induction period (IP) decreased gradually with increasing storage temperature in both oils. WO showed shorter IPs (23.0, 9.2, and 1.0 day at 25, 40, and 60°C, respectively) than those of GSO (41.5, 12.0, and 1.8 day at 25, 40, and 60°C, respectively), indicating the higher susceptibility of WO to oxidation. The activation energy (Ea) for the IP of WO and GSO autoxidation was similar (75.87 and 75.66 kJ/mol, respectively), revealing similar temperature dependence for autoxidation in WO and GSO.

Anioxidative and radical scavenging activities of propolis extracts in food models

Propolis samples collected from Mwingi, Malindi, Uasin-gishu and Meru south districts in Kenya were extracted using ethanol and methanol. The methanol extracts were further partitioned into ethyl acetate, hexane and aqueous fractions. The extracts were concentrated and dried in vacuum evaporator. Their antioxidative activities were tested in linoleic acid-â-carotene system and in soybean oil. The extracts’ radical scavenging activities against 2,2–diphenyl-1-picrylhydrazil (DPPH) were also studied. Significant differences were observed between the samples as well as within the samples’ various extracts. The ethanol extract of propolis (EEP) and the ethyl acetate fractions from all four samples had higher 2,2–diphenyl-1-picrylhydrazil (DPPH) radical scavenging activity compared to the aqueous and the hexane extracts at a concentration of 500 ig/ml. Malindi EEP at a concentration of 500 ig/ml had a significantly (p < 0.05) higher radical scavenging activity (87.7%) than all the other EEP’s. The least radical scavenging activity was observed in Uasin-gishu EEP with 73.3%. The Mwingi ethyl acetate extract at a concentration of 500 ig/ml had 79.2% radical scavenging activity which was the highest observed amongst the ethyl acetate fractions and the least was in Uasin-gishu sample having 66.1% activity. The highest activity among the aqueous extracts was 7.1% in Meru South sample at a concentration of 500 ig/ml. Radical scavenging activity did not differ in all four aqueous fractions. There was no significant difference (p < 0.05) observed in the antioxidation activity of Mwingi, Meru south and Malindi EEPP’s, in the linoleic acid-â-carotene system at a concentration of 500 ig/ml. The EEP’s were the most active against oxidation of the system with a range of 61.7% in Uasin-gishu sample to 71.8% in Malindi sample while the aqueous was the least active with a range of 5.8% to 11.7% in Uasin-gishu and Malindi samples respectively. The EEP’s at a concentration of 1mg/ml showed greater activity against antioxidation of soybean oil compared to butylated hydroxyltoluene (BHT) at a concentration of 0.2 ig/ml for the first 25 days of the test. After the 25th day, there was sharp increase in peroxide values in all the EEPs showing loss of antioxidation strength. Key words : Propolis, Radical scavenging, antioxidation activity

Oxidative stability of shrimp oil-in-water emulsions as affected by antioxidant incorporation

Shrimp oil is one of the important sources of n-3 fatty acids, which have been known for health benefit. The incorporation of shrimp oil into food emulsion has gained increasing interest. Since shrimp oil is rich in unsaturated fatty acids, it is susceptible to oxidation, leading to development of off-odor and loss in nutritive value. Thus, this study aimed to investigate the oxidative stability shrimp oil-in-water emulsion (pH 3.6) incorporated with various antioxidants at different levels during the storage at 30°C for 12 days. With increasing storage time, progressive formation of hydroperoxide was found in all samples as evidenced by the increase in peroxide values (PV) (p < 0.05). The lower PV was found in those added with antioxidants; however PV values varied with different antioxidants added. Sample added with 200 ppm α-tocopherol alone had the higher PV than others (p < 0.05). The increase in thiobarbituric acid reactive substances (TBARS) of the control, sample added with 200 ppm α-tocopherol and that containing 500 ppm lecithin were noticeable when storage time increased (p < 0.05). Slight increases in TBARS were found in samples added with mixed antioxidants including 50 ppm EDTA + 100 ppm tannic acid, 50 ppm EDTA + 200 ppm α-tocopherol, 50 ppm EDTA + 100 ppm tannic acid + 200 ppm α-tocopherol or 50 ppm EDTA + 100 ppm tannic acid + 500 ppm lecithin + 200 ppm α-tocopherol throughout 12 days of storage (p < 0.05). This was concomitant with the decreased formation of volatile compounds and rancid off-odor in emulsion containing mixed antioxidants, especially 50 ppm EDTA + 100 ppm tannic acid and 50 ppm EDTA + 100 ppm tannic acid + 500 ppm lecithin + 200 ppm α-tocopherol. Thus, the use of EDTA in combination with tannic acid could retard the lipid oxidation in the shrimp oil-in-water emulsion more effectively, compared to other combinations of antioxidants tested.

A lipid peroxidation product 9-oxononanoic acid induces phospholipase A2 activity and thromboxane A2 production in human blood

Lipid peroxidation products are known to cause toxicity by reacting with biologically significant proteins, but the inducing role of peroxidation products has been not noted to produce degenerative disease-related eicosanoids. Here, 9-oxononanoic acid (9-ONA), one of the major products of peroxidized fatty acids, was found to stimulate the activity of phospholipase A2 (PLA2), the key enzyme to initiate arachidonate cascade and eicosanoid production. An exposure of fresh human blood to the atmosphere at 37°C accumulated 9-ONA, increasing peroxide value and thiobarbituric acid reactive substances in the blood. The lipid peroxidation was accompanied by significant increases of PLA2 activity and thromboxane B2 (TxB2) production, which is a stable metabolite of thromboxane A2 (TxA2) and a potent agonist of platelet aggregation. These events were abolished by standing the blood under nitrogen. The addition of organically synthesized 9-ONA resumed the activity of PLA2 and the production of TxB2. Also, 9-ONA induced platelet aggregation dose-dependently. These results indicated that 9-ONA is the primary inducer of PLA2 activity and TxA2 production, and is probably followed by the development of diseases such as thrombus formation. This is the first report to find that a lipid peroxidation product, 9-ONA, stimulates the activity of PLA2.

Evaluation of gamma irradiation and frozen storage on microbial load and physico-chemical quality of turkey breast meat

In this study we evaluated the effects of gamma irradiation at doses of 0.0, 0.5, 2.0 and 4.0kGy and frozen storage as a combination process on improvement of turkey breast meat shelf life. The samples were stored at −18°C and were undergone microbial, chemical and sensory evaluation at 2-month intervals. However, 4kGy dose reduced the counts of mesophilic bacteria and coliform by more than 5 log units, while Salmonella was not detected. Irradiation of samples significantly increased peroxide value but had no significant effect on total volatile nitrogen contents, while storage significantly increased the peroxide value and total volatile nitrogen.

Cyto-genotoxic and oxidative effects of a continuous UV-C treatment of liquid egg products

UV-C treatment of food is a promising non-thermal processing technology to improve food safety and preservation. Most of the chemical constituents of food absorb UV-C light that can lead to chemical modifications and quality changes. This work investigated the effects of UV-C treatment of liquid egg products on lipid, protein oxidations and potential cyto- and genotoxic effects on intestinal epithelial cells in vitro. Egg preparations (egg white, yolk, liquid whole egg) were treated with UV-C (254nm, volumetric doses between 0 and 115,619JL−1) using a commercial UV-C processing unit equipped with a Dean Flow reactor. UV-C treatment at high doses (from 32,181JL−1, about 2 times higher than that needed to inactivate 5log of relevant microorganisms) showed an increased lipid oxidation in egg yolk and slight effects in liquid whole eggs; this was confirmed by slightly but not statistically significant increased peroxide values. UV-C induced also slight protein damage, characterised by the total sulfhydryl group reduction. These UV-C-induced oxidative modifications in egg preparations however did not cause any increase in the cyto- or genotoxic (DNA strand breaks) effects in intestinal Caco-2 cells.

The use of olive leaves and tea extracts as effective antioxidants against the oxidation of soybean oil under microwave heating

Vegetable oils are prone to oxidative processes which lead to quality and nutritional losses, particularly under microwave heating, increasingly used in culinary procedures. Natural antioxidants can be regarded as good strategies in the inhibition of oxidation during culinary processing. In this work the addition of white tea and olive leaves aqueous extracts to soybean oil were evaluated as possible oxidative stabilizers during microwave heating (0–15min; 1000W). Microwave heating caused severe quality, nutritional and compositional losses, mainly beyond three minutes of heating, with marked increase in peroxide value, K232, and K270. Olive leaves extracts increased the vitamin E availability in the samples, were able to reduce the formation of oxidation compounds, and exhibited a higher protection against polyunsaturated fatty acids loss. White tea extracts provided higher antioxidant activity and oxidative resistance to the soybean oils. The use of natural antioxidants could be an effective way to protect soybean oil, one of the most important world crops, from oxidation.

Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei): Compositions and deterioration as affected by iced storage

Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) stored in ice for up to 6 days were extracted and characterised. The extraction yields of lipids from hepatopancreas (10.65-12.64%) were higher than those from cephalothorax (2.59-2.88%). However, no changes in the extraction yield were observed during the storage (p>0.05). The carotenoid contents of lipids from cephalothorax and hepatopancreas slightly increased within the first 2 and 4 days of iced storage (p<0.05), respectively, but decreased thereafter (p<0.05). With increasing storage time, a progressive formation of hydroperoxide was found as evidenced by the increase in the absorbance band at 3600-3200 cm(-1) in Fourier transform infrared (FTIR) spectra, and increased peroxide values (PVs) (p<0.05). The increases in thiobarbituric acid reactive substances (TBARS), p-anisidine value (AnV) and free fatty acid (FFA) content of lipids were noticeable when iced storage time increased (p<0.05). Those changes indicated that lipid oxidation and hydrolysis occurred in both samples. Phospholipids (PL) were the major components in lipids from cephalothorax (82.51% of total lipids). Nevertheless, lipids from hepatopancreas contained triglyceride (TG) and PL as the dominant components (45.35% and 38.03% of total lipids, respectively). A decrease in the TG content with a concomitant increase in free fatty acid was observed at the end of storage (day 6) (p<0.05). Decreases in unsaturated fatty acids, especially eicosapentaenoic acid (EPA; C20:5(n-3)) and docosahexaenoic acid (DHA; C22:6(n-3)) were noticeable at day 6 of storage (p<0.05). Thus, the extended storage time resulted in the enhanced deterioration of extracted lipids.

Evaluation of Some Chemical Properties of Butter Enriched With Hazelnut and Walnut Powders

Consumption of food containing cholesterol and saturated fatty acids such as butter can increase serum cholesterol and cause cardiovascular diseases. Therefore many efforts have been done for decreasing these constituents in foods. In this study, hazelnut and walnut powders were added to butter samples in amounts of 0 (not enriched sample), 10, 20 and 30% for evaluation of chemical characteristics (acid value, peroxide value and oxidative stability). Samples were then packed in 2 forms; vacuum and common packed and stored for 90 days at 5°C in refrigerator and were analyzed every 30 days. Adding hazelnut and walnut to butter samples caused significant increase in acid value of samples. Also rising trend of acid value in nut enriched samples was higher during storage. Control samples (without nut) showed higher peroxide value than nut enriched samples. During storage both control and nut enriched samples showed significant increase in peroxide value . Although all of nut enriched samples’ peroxide value were lower than standard limit during storage. Vacuum packed samples also showed lower acid and peroxide value than common packed samples. Adding nuts to butter samples also caused a decrease in oxidative stability of butter samples. This study shows that butter enriched in hazelnut and walnut can be introduced as a new and functional dairy product to consumers, because of its essential fatty acids content. Keywords: Butter, Walnut, Hazelnut, Oxidative Stability, Acid Value, Peroxide Value

Changes in phospholipid composition, protein content and chemical properties of flaxseed oil during development

The aim of the present research is to investigate the effect of harvest date on the composition of flaxseed. Samples were collected at regular intervals from 7 to 56 days after flowering (DAF) and analyzed for phospholipid composition, storage protein content and chemical properties. Phospholipid (PL) percentage of the total lipid decreased from 32.72% on the 7th DAF to 2.55% on the 56th DAF. The most phospholipids present in flaxseed were phosphatidylinositol (PI), phosphatidylethanolamine (PE) and lysophosphatidylcholine (LPC) which were highly unsaturated and rich in linolenic and linoleic acids, comprising together 60% of the total fatty acids. Chemical investigation of flaxseed oil showed overall a decrease in UV absorbance (K(232) and K(270)), acid value, free fatty acid content and an increase in peroxide value and storage protein content with development. At full maturity, flaxseed contained 29% proteins on a dry weight basis (DW %).

Efecto de la adición de ajo en la estabilidad y calidad sensorial de una pasta de aceituna

The effect of garlic on the quality and stability of olive paste was evaluated. A control paste (Pc) was prepared based on a Sevillana olive variety, the other was identical to Pc with 0.5g/100g of garlic (Pa). Microbiological, physicochemical and sensory changes were monitored in both pastes at time zero and during storage up to 90 days at 4°C. Microbiological parameters remain within acceptable limits from the point of view of health. The addition of garlic to the olive paste leads to increased acidity (% lactic acid) and a significant decrease (p < 0.05) in pH at 30 and 60 days of storage. The addition of garlic produces a lower increase in peroxide value after 90 days of storage. An instrumental color analysis indicates that Pa is brighter and has greater color intensity. Acceptability is similar between the pastes. The sensory quality indicates that Pa has better appearance, aroma, texture and flavor. Rancidity is less than perceived in Pa. The tastes sour, salty and bitter are lower in Pa. According to the results, the addition of garlic is recommended for olive paste and similar foods.

Study on Antioxidative Effect of Lycopene to the Photosensitized Oxidation of Soybean Oil

A research was designed to study the effect on inhibiting the photosensitized oxidation of natural (lycopene) and synthetic (tertiary butylhydroquinon, TBHQ) antioxidant in soybean oil. In the presence of light, mean value of all samples revealed that a significant increase in peroxide value, free acid value and thiobarbituric acid (TBA) assay. The addition of lycopene and TBHQ reduced the peroxide value of control sample from 12.810 to 7.378 and 9.882 meq/kg, respectively. And TBA was found to be 0.163 in control sample, while the values of lycopene and TBHQ treatments were 0.080 and 0.134. Meanwhile, the oil samples were treated with different does of lycopene under light, the rate of oxidation increased considerably with a corresponding decrease in the content of lycopene. The data showed that oils containing 300 ppm lycopene had the lowest levels of free fatty acid value.The results indicated that lycopene in soybean oil exposed to light were found to be effective in inhibiting lipid oxidation.

Effect of microwave heating of linseed oil on the formation of primary and secondary oxidation products

The purpose of the present study was to explore the influence of microwave heating for different periods on the primary and secondary oxidation, total oxidation as well as conjugation of stripped and non-stripped linseed oils. Color index of the oil samples was also evaluated to show changes of color during periodical heating. It was generally found that a significant increase in peroxide value, p-anisidine, total oxidation, conjugated diene and conjugated triene for microwave heating periods of 1,2,3,4 and 5 min. Two samples (stripped and non-stripped) of linseed oil (microwave treated) were analyzed individually in triplicate, and the results were reported as mean ±SD. Statistical significance of the differences between mean values was assessed by one-way ANOVA. It was found that stripped linseed oil (absence of antioxidants) is prone to heat effect than the non-stripped oil (with antioxidants). Generally, it is recommended that polyunsaturated oils have to be prevented from heat treatment for cooking purposes (e.g. soybean and linseed oils), since they contain linoleic and linolenic acids which are sensitive to oxidation.