Lipid oxidation in chicken as affected by cooking and frozen storage

Oxidative rancidity in fresh, frozen and cooked chicken breast and leg meat was evaluated by measuring malondialdehyde (MDA) in fat from meat with an improved 2-thiobarbituric acid (TBA) assay with antioxidant protection, and by measuring the relative fluorescent products of organic and aqueous layers from Folch extracted meat. Fresh samples were frozen for 3 and 6 months at ?18 °C and cooked in convection and microwave ovens. Frozen storage for 3 and 6 months either before cooking or after convection and microwave cooking substantially increased MDA concentrations in fat from meat, whereas cooking was more effective in generating fluorescent products. There were no significant differences in free MDA concentrations or TBA numbers in chicken meat between convection and microwave cooking methods. The certain secondary fluorescent products were significantly higher in meat cooked by convection oven. The initial levels of either MDA or fluorescent products in meat are of primary importance in determining the final MDA and fluorescence levels after processing.     

Soy Protein Isolate Solubility and Surface Hydrophobicity as affected by Antioxidants

Addition of tert-butylhydroquinone or a mixture of butylated hydroxyanisole and tert-butylhydroquinone (200 ppm on a lipid basis) during SPI processing gave increased protein solibility over that of the control (55%. 56% and 34%. respectively). These increased solubilities correspond to 32% and 18% decrease in oxidation of free sulfhydryls and 20% and 12% reduction in protein oxidation, as determined by protein carbonyl content. Increased protein solubilities, due to added antioxidants, were accompanied by higher total protein surface hydrophobicity, as determined by the sodium dodecyl sulfate (SDS) binding method, and soluble protein hydrophobicity, as determined by the fluorescence probe 8-anilino-1-naphthalene sulfonate (ANS).     

Lipid Oxidation in Cooked Turkey as Affected by Added Antioxidant Enzymes

Catalase (CAT) and glutathione peroxidase (GSH-Px) were added to turkey which had been cooked (80°C) to provide minimal activity of both enzymes, to determine their effects in development of lipid oxidation. CAT (100–500 U/g muscle) decreased the formation of thiobarbituric acid reactive substances (TBARS) 4–28% during 2 days of storage. GSH-Px (4.0 U/g muscle) decreased TBARS 8–11%. CAT (170 U/g muscle) and GSH-Px (1.3 U/g muscle) in combination decreased TBARS formation 7–14%. Reduced glutathione concentrations in the turkey were unaffected by cooking. These data suggest that heat inactivation of CAT and GSH-Px was not the only factor involved in heat-induced lipid oxidation reactions in turkey thigh muscle.     

肉制品中脂肪氧化与蛋白质氧化及相互影响

近年来,食品中脂肪氧化与蛋白质氧化之间的联系在国内外引起了广泛关注。肉制品中脂肪及蛋白质的氧化能产生特征风味,但更多的是引起风味的劣化和颜色的褪变,且脂肪氧化和蛋白氧化之间是相互关联的,彼此相互促进。针对由脂肪氧化和蛋白质氧化影响肉制品品质的问题,就脂肪氧化与蛋白质氧化机理、肉制品中脂肪与蛋白质氧化的相互影响关系及控制措施进行综述。     

Lipid Peroxidation in Chicken Meat During Chilled Storage as Affected by Antioxidants Combined with Low-Dose Gamma Irradiation

TBA values and carbonyl content for irradiated samples of ground chicken meat were higher than for nonirradiated samples. Addition of antioxidants tocopherol (natural) or BHT (synthetic) resulted in retardation of oxidative rancidity (p<0.05). Meat treated with antioxidants prior to irradiation had lower TBA values as compared to untreated irradiated counterparts. Free fatty acid (FFA) values decreased after irradiation. Addition of antioxidants prior to irradiation showed a synergistic effect in decreasing FFA content. TLC of muscle lipids indicated a reduction in the triacylglcerols content with concomitant increases in FFA of all samples during storage. All irradiated meats were acceptable for consumption up to 4 wk of storage.     

Physicochemical properties of thawed chicken breast as affected by microwave power levels

The main objective of this study was to determine the effect of microwave thawing at different power levels on the physicochemical properties of chicken breast. Each frozen chicken breast samples were thawed in microwave oven at microwave power levels of 125, 250, and 375W. To compare the effect of microwave thawing on meat quality, refrigerator thawing was used as a control. As the microwave power level increased, the thawing rate increased and temperature differences between the edge position and center position of the samples also increased. Treatment at a power level of 250 W resulted in a lower thawing loss and a higher moisture content, water holding capacity, and tenderness than the other treatments (p<0.05). However, there were no significantly differences of proximate composition excluding moisture content, pH, lightness, and yellowness. The use of excessive input energy during microwave thawing (higher microwave power level) damaged the physicochemical properties of the thawed chicken breast; therefore, the microwave power level of 250 W is the best thawing method on the frozen chicken breast to minimize the changes in meat quality in this study.     

鱼类血红蛋白诱导脂质氧化及其控制的研究进展

脂质氧化不仅使食品的营养、风味、质构和外观发生变化,而且缩短了产品的货架期,降低其食用品质,是造成水产食品品质劣变的重要原因之一。血红蛋白是水产品脂质氧化的重要诱导因子,其自动氧化产生的高铁血红蛋白可以加速脂质氧化反应速率,同时释放的血红素和铁离子也可催化脂质氧化的发生。化学防腐剂在食品中的应用越来越受到限制,天然抗氧化剂的研究与应用已成为热点,了解血红蛋白促氧化的机理,找到适宜的抗氧化技术,有效地控制水产品在贮藏过程中血红蛋白诱导的脂质氧化的发生是非常必要的。因此,本文以血红蛋白诱导的脂质氧化为切入点,介绍了鱼类血红蛋白的结构、促氧化的反应机理和影响因素,以及天然酚类抗氧化物在控制血红蛋白促氧化方面的诸多应用与进展,并提出了目前急需解决的问题和未来的研究趋势。     

Lipid Oxidation, Volatiles and Color Changes of Irradiated Pork Patties Affected by Antioxidants

Changes were measured in TBARS, color, and volatiles of irradiated (4.5 kGy) pork patties with antioxidants (sesamol, quercetin, rutin, BHT, and rosemary oleoresin) during 7 days storage at 4°C. Irradiation accelerated lipid oxidation of raw pork during storage. However, irradiation before cooking did not influence lipid oxidation of cooked pork during storage. Sesamol, quercetin, and BHT were effective in both irradiated raw and cooked pork during 7-days storage. Rosemary oleoresin and rutin were effective only in irradiated raw pork for 3 days. Hexanal, propanal and higher boiling components were well correlated (P < 0.01) with TBARS in cooked pork. Generation of volatiles was reduced by sesamol and quercetin, but the effects of antioxidants on color changes of raw pork patties were minor and inconsistent.     

Iron-Catalyzed Oxidation of Menhaden Oil as Affected by Emulsifiers

The ability of Tween 20 and whey protein isolate (WPI) to influence lipid oxidation was investigated by evaluating the effects of emulsifier concentration and physical location on iron-catalyzed oxidation of emulsified Menhaden oil. Addition of Tween 20 or WPI to the aqueous phase of a 0.5 wt% Tween 20 stabilized emulsion increased lipid oxidation as determined by both thiobarbituric acid reactive substances (TBARS) and lipid peroxides. Tween 20 (2.0 wt%) and WPI (0.05–1.0 wt%) combinations inhibited TBARS formation 23–60%. Oxidation of a WPI-stabilized emulsion decreased with decreasing pH (3–7) but in a Tween 20 stabilized emulsion oxidation increased with decreasing pH. The low oxidation rate for the WPI-stabilized emulsion at pH 3 was increased when Tween 20 displaced WPI from the droplet interface. Results indicate that the oxidative stability of emulsifed Menhaden oil could be increased by controlling emulsifier type, location and concentration.     

Lipid and cholesterol oxidation in chicken meat are inhibited by sage but not by garlic

The effects of the addition of sage and garlic in chicken meat on lipid and cholesterol oxidation, having as prooxidant factors the addition of salt, thermal treatment, and frozen storage, were evaluated. The content of unsaturated fatty acids did not change in the presence of sage; on the contrary, with garlic, the content of these fatty acids decreased after cooking and storage. Hexanal and pentanal contents were lower in patties containing sage, and higher in those with garlic. The 7-ketocholesterol was the cholesterol oxide found in higher amount in raw chicken on day 0, while the formation of 7β- and 7α-hydroxycholesterol was verified only from day 30 on. Cooking and storage resulted in increase of total cholesterol oxides and decrease of α- and γ-tocopherol. Sage was effective in controlling lipid and cholesterol oxidation, minimizing the prooxidant effects of salt, cooking, and storage. However, garlic presented no effect as antioxidant and accelerated lipid oxidation. PRACTICAL APPLICATION: The addition of sage to chicken meat (0.1 g/100 g) is a good alternative to prevent and delay the formation of compounds derived from lipid oxidation that are responsible for off-flavors and loss of nutritional quality during long-term frozen storage. Care must be taken when using garlic to seasoning chicken meat products, such as hamburgers and meatballs, especially cooked or precooked due to its potential to promote lipid oxidation and consequently raising the risk of having the product rejected by the consumer.     

Water holding capacity of sodium-reduced chicken breast myofibrillar protein gel as affected by combined CaCl2 and high-pressure processing

The water holding capacity (WHC) of sodium-reduced (0.3 m sodium chloride, corresponding to the salt percentage (w/v) of 1.755%) myofibrillar protein (MP) gel in response to combined calcium chloride (CaCl₂, 20, 60, 100 mm ) and high-pressure processing (HPP, 200 MPa, 10 min) was investigated. The results showed that 200 MPa + 20 mm CaCl₂ synergistically increased the WHC of MP gel via reducing particle size of MP solutions, strengthening hydrogen-bonding and disulphide-bonding, promoting formation of β-sheet and uncoiling of α-helix, exposing tryptophan residues, enhancing hydrophobic interactions of aliphatic residues and forming a compact and continuous networked gel structure. However, high concentrations (≥60 mm ) of CaCl₂ could attenuate the enhancing effects of HPP on the WHC by inducing decreased hydrogen bonds, fewer tryptophan residues exposed and coarser and aggregated gel structures with large cavities. Therefore, a combined moderate HPP and low concentration of CaCl₂ is a potential alternative for developing sodium-reduced meat products.     

Evaluation of lipid oxidation and oxidative products as affected by pork meat cut, packaging method, and storage time during frozen storage (-10 degrees C)

ABSTRACT:  Lipid oxidation and oxidative volatiles as affected by pork meat cut and packaging method during frozen storage at –10 °C were evaluated. Pork belly cut had higher thiobarbituric acid reactive substance (TBARS) and pH values than did the loin, whereas the loin had higher free fatty acid (FFA) values than that of the belly cut. Peroxide values increased with increased storage time, but were not affected by pork meat cut and packaging method. Volatiles with carbon numbers less than 10 in the belly cut were higher than those in the loin cut, whereas those with carbon numbers greater than 10 in the loin cut were higher than those in belly cut. Most volatiles were decreased with increased storage time, except for propane. Both 4-pentenal and 4-methyl-2-hexanone in the belly cut showed a positive correlation with FFA, whereas 2,4-dimethyl-1-heptene and 9-octadecenal in the loin cut were positively correlated with TBARS and FFA, respectively, even though the values were not high enough to predict the degree of lipid oxidation.     

The production of volatile compounds in model casein systems with varying fat levels as affected by low-frequency ultrasound

The effects of low-frequency ultrasound on the production of volatile compounds in model casein protein systems containing various fat concentrations of 2%, 4% and 6% (w/w) were investigated. Ultrasound application was performed at 20 kHz for up to 10 min which corresponded to energy densities ranging from 9.54 to 190.8 J mL⁻¹. Similar volatile compounds were detected both in pure fat and mixtures of casein and fat (CF) systems. These volatiles belonged to the groups of aldehydes, ketones, esters, alcohols and hydrocarbons, which were the products of oxidation of lipids or protein degradation due to acoustic cavitation. The amount of fat in the casein systems had minor effects on the production of volatiles, whereas the production of volatile compounds was significantly affected by the ultrasound treatment. Short sonication times <5 min generated similar volatile profiles to the untreated samples. In contrast, prolonged sonication for 5 and 10 min considerably increased the production of volatile compounds and the amounts of fatty acids. Thus, the application of low–frequency ultrasound for short periods should be considered to minimise the production of volatile compounds which can ultimately affect the taste.     

The effects of brined onion extracts on lipid oxidation and sensory quality in refrigerated cooked turkey breast rolls during storage

The effects of brined onion extracts on selected aspects of quality in cooked encased turkey breast rolls were evaluated during refrigerated storage over 7 days. Using the thiobarbituric acid (TBA) assay, a 50% strength juice gave a significant reduction (P < 0.0001) in lipid oxidation in both 100 g and 1 kg rolls relative to controls. Quercetin, the main onion juice antioxidant, was reduced by 65% in freshly cooked 1 kg rolls compared with raw rolls but changed little thereafter in storage. Cook yields were significantly higher for rolls containing added onion extracts than for controls (P < 0.05) but no colour differences were detected using Hunter Lab values (P ? 0.05). A 30-member untrained sensory panel expressed no preference for freshly opened 4 day-stored control or onion extract-supplemented rolls packed in plastic casings but there was a significant preference (P < 0.05) for the onion extract product when 4 mm thick meat slices were stored in air for an additional 24 h.     

Lipid oxidation and colour in pressure‐ and heat‐treated minced chicken thighs

Lipid oxidation and colour in pressurised and heated chicken samples were evaluated. In a preliminary test, raw and overcooked (100 °C/60 min) minced chicken thighs were pressurised (500 MPa/50 °C/30 min). Samples were stored at 4 °C in contact with air. Thiobarbituric acid reactive substances (TBARS) were quantified at 1, 6 and 9 days. Pressure induced oxidation in chicken, but overcooking generated many more secondary oxidation compounds. In a second experiment, raw minced chicken thighs were pressurised (500 MPa/?10, 5, 20 and 50 °C/30 and 60 min) or cooked (90 °C/15 min). Samples were vacuum stored at 4 °C. TBARS were measured at 1 and 9 days, whereas colour parameters (L, a, b and ΔE) were determined at 1 day. No differences in TBARS values were observed between untreated and pressurised samples, whereas cooked samples presented the highest values. Pressurisation for 30 and 60 min generated similar TBARS contents. At 9 days, oxidation values did not increase. Pressurisation and cooking induced marked colour changes. Pressurised samples were lighter and less red than untreated ones. Samples pressurised at 50 °C were the palest and, together with cooked samples, presented the lowest a values. Therefore pressurised chicken thigh cannot be marketed as a fresh product but can be incorporated as an ingredient in ready‐to‐eat meals. Copyright © 2004 Society of Chemical Industry     

酶氧化鸡脂制备鸡肉味香料前体物

采用大豆脂肪氧合酶催化氧化鸡脂,以过氧化值为评价指标,通过单因素及正交试验确定了鸡脂控制氧化的较优反应条件,探讨了时间、pH值、温度等因素对氧化反应的影响。结果表明,在反应温度10℃,反应时间5h,底物浓度225g/L,pH值为9,空气流速0.2m3/h时,氧化鸡脂的过氧化值最高,最高过氧化值为180mmol/kg脂肪。     

Antioxidants, Activators, and Inhibitors Affect the Enzymic Lipid Peroxidation System of Catfish Muscle Microsomes

Various promoters and inhibitors of enzymic lipid peroxidation in catfish were investigated. At 100 ppm BHA, BHT, NDGA, TBHQ, PG, EDTA, STPP, TDPA, THBP, and ethoxyquin completely inhibited lipid peroxidation activity. Natural antioxidants, a-tocopherol, P-carotene, and rosemary powder, had moderate inhibitory effects. Sodium ascorbate and erythorbate at a concentration of 100 ppm activated lipid peroxidation; however, higher concenlrations of these antioxidants had inhibitory effects. Unlike ferric and ferrous ions, Cu⁺⁺ ions at 0.015 mM did not catalyze lipid peroxidation. Inorganic pyrophosphate and phosphate at 0.1 mM chelated ferric ion and inhibited lipid peroxidation.