Sulfurous Off-Flavor Formation and Lipid Oxidation in Heat-Sterilized Meat in Trays

The development of a strong sulfurous off-flavor as compared to lipid oxidation in heat-sterilized meat in trays was investigated. Hydrogen sulfide and ethane were used as indicators for sulfurous off-flavor and lipid oxidation, respectively. Nitrogen flushing suppressed oxidation but greatly enhanced formation of hydrogen sulfide. Concentrations of hydrogen sulfide were lower in HTST-processed meat and also decreased during storage of both nonflushed and nitrogen-flushed samples. The addition of rosemary extract as primary antioxidant lessened both hydrogen sulfide and ethane formation for a limited storage period. Citric acid as the secondary antioxidant had little effect. Use of a primary antioxidant and application of HTST process conditions seemed to balance hydrogen sulfide and ethane formation.     

Rosemary Extract and Precooking Effects on Lipid Oxidation in Heat-Sterilized Meat

The influence of precooking and addition of refined rosemary extract on lipid oxidation during storage of heat-sterilized meat in trays was investigated. Short precooking resulted in increased lipid oxidation, while more extended precooking using peanut oil gave products with higher stability during storage. The addition of a gravy-type sauce (instead of water) to the meat when filling it into trays also resulted in higher storage stability. However, only the application of rosemary extract, especially after precooking, resulted in products with stability similar to those packed with nitrogen flushing.     

Volatiles and Oxidative Changes in Irradiated Pork Sausage with Different Fatty Acid Composition and Tocopherol Content

Aerobic-packaged sausage irradiated at 4.5 kGy had higher (P < 0.05) 2-thiobarbituric acid reactive substances (TBARS) than those irradiated at 0 or 2.5 kGy at 0-d storage. Generally, TBARS of aerobic- or vacuum-packaged sausage prepared with lard were higher (P < 0.05) than those of sausage prepared with flaxseed oil or corn oil. The amount of 1-heptene and 1-nonene increased (P < 0.05) with increased irradiation doses. Aldehydes, ketones, and alcohols were not influenced by irradiation at 0-d storage. However, irradiation accelerated lipid oxidation and increased the amount of aldehydes, ketones, and alcohols in aerobic-packaged sausage during storage. The tocopherol content in the sausage influenced (P < 0.05) production of volatiles at different levels of unsaturated fatty acids.     

天然抗氧化剂对控制猪肉脂肪氧化及保鲜效果研究

利用蜂胶、茶多酚、迷迭香提取物等天然抗氧化剂配制成2种复合抗氧化液(水溶性和脂溶性)对冷却猪肉进行抗氧化及保鲜效果比较。结果表明,2种复合抗氧化剂可以有效地控制脂肪氧化,显著降低了氧化酸败异味的产生。同时发现,天然脂溶性复合抗氧化剂对鲜肉有明显抑菌和防腐作用,从而起到了抗氧化和保鲜双重功效。     

贮藏条件对猪肉糜氧化效应的影响

将肥瘦比为1:1的猪糜于-18、-24、-40℃三种条件下贮藏,每10d取样一次,通过测定酸价（AV）、过氧化值（POV）和硫代巴比妥酸（TBARS）值,研究贮藏温度、贮藏时间对猪肉糜氧化效应的影响。结果表明,贮藏时间和温度显著影响肉糜的氧化进程（p<0.05）,随贮藏时间的延长,酸价整体呈先上升后下降的趋势,而过氧化值、硫代巴比妥酸值整体呈上升趋势;贮藏温度越低,肉糜的AV值、POV值和TBARS值也越低,且变化缓慢。缩短贮藏时间和降低贮藏温度有利于控制肉糜脂肪氧化,研究表明,贮藏时间小于20d时效果最佳,30d时脂肪水解与氧化达到了动态平衡;-40℃贮藏效果最好,但从节能等角度综合考虑,-24℃更适合作为肉糜长期贮藏的温度。      

Packaging and Irradiation Effects on Lipid Oxidation and Volatiles in Pork Patties

Raw-meat patties were prepared from three pork muscles, irradiated in different packaging environments, and stored for 0 or 3 days before cooking. Lipid oxidation by-products were formed in the raw meat during storage and the baseline lipid oxidation data of raw meat was used to measure the progression of lipid oxidation after cooking. Thiobarbituric acid-reactive substances (TBARS) and volatiles data indicated that preventing oxygen exposure after cooking was more important for cooked meat quality than packaging, irradiation, or storage conditions of raw meat. Propanal, pentanal, hexanal, 1 -pentanol, and total volatiles correlated highly (P < 0.01) with TBARS values of cooked meat. Hexanal and total volatiles represented the lipid oxidation status better than any other individual volatile components.     

Antioxidant Activity of Phosvitin in Phosphatidylcholine Liposomes and Meat Model Systems

ABSTRACT: Phosvitin, an iron-chelating protein, was tested for its ability to inhibit lipid oxidation in phosphatidylcholine (PC) liposomes and meats. Inhibition of thiobarbituric acid reactive substances (TBARS) formation increased with increasing phosvitin concentrations with maximal inhibition occurring at 40 and 15 mM in PC liposomes and pork muscle homogenates, respectively. Phosvitin lost only 2 to 15% of its antioxidant activity after being heated for 10 min at 60 to 100 °C. The ability of phosvitin to inhibit TBARS formation was maximal at pH 7.0. Phosvitin was a more effective antioxidant in cooked ground pork with 20 mM inhibiting 11 to 39% of oxidation compared with 0 to 20% inhibition in uncooked, salted ground pork containing 60 mM phosvitin.     

Effect of Antioxidants on the Production of Off-Odor Volatiles and Lipid Oxidation in Irradiated Turkey Breast Meat and Meat Homogenates

The addition of gallate, sesamol, trolox, and tocopherol was effective, but sesamol, sesamol + tocopherol, and gallate + tocopherol were among the most effective antioxidants in reducing thiobarbituric acid reactive substances, volatile production, and off‐odor intensity in turkey breast homogenates. Also, these 3 antioxidant treatments were effective in controlling lipid oxidation and off‐odor intensity in both vacuum and aerobically packaged patties. However, aerobic packaging was better than antioxidant treatments in reducing off‐odor intensity of irradiated turkey patties. Antioxidants had no effect on redness, but increased lightness and yellowness of irradiated turkey breast. It was concluded that a combination of antioxidant and aerobic packaging was more useful than antioxidant and vacuum packaging in controlling off‐odor problems in irradiated raw turkey meat.     

Catalytic Mechanism of Lipid Oxidation following High Pressure Treatment in Pork Fat and Meat

Addition of citric acid (0.02%) inhibited the increased rate of lipid oxidation found in rendered pork fat following pressure treatment (650-800 MPa). This indicated that transition metal ions were probably released from complexes and became available to catalyze lipid oxidation in the pressure treated fat. In minced pork and washed fibers citric acid was less effective in inhibiting oxidation in pressure treated samples because of its pH lowering effects. However, the less acidic ethylenediaminetetraacetic-acid disodium salt (Na₂EDTA) was an effective antioxidant in these pressure treated (400 MPa and 800 MPa) systems. This further indicated that metal catalysts (probably iron) were released from complexes during pressure treatment to catalyze lipid oxidation.     

不同包装形式和复合天然抗氧化剂对猪肉脂肪氧化的影响

利用蜂胶、茶多酚、迷迭香提取物等天然抗氧化剂配制成两种复合抗氧化液(水溶性和脂溶性)对冷却猪肉处理后,分别采用托盘包装、聚乙烯薄膜袋包装和真空包装,对两种复合抗氧化液进行抗氧化及保鲜效果比较。结果表明:两种复合抗氧化剂可以有效地控制脂肪氧化,显著的降低了氧化酸败异味的产生。同时发现,天然脂溶性复合抗氧化剂对鲜肉有明显抑菌和防腐作用,从而起到了抗氧化和保鲜双重功效。两种抗氧化液和真空包装同时应用抑制脂肪氧化和保鲜的效果更好。     

Lipid Oxidation in Cooked Pork as Affected by Vitamin E, Cooking and Storage Conditions

The individual and combined effects of muscle vitamin E level, cooking conditions (duration, temperature and rate) and packaging on lipid oxidation in refrigerated cooked pork were examined. Oxidative stability following cooking was higher in pork with a higher vitamin E level (p<0.01), cooked at a lower cooking temperature (p<0.01), cooked for a shorter time (p<0.01), cooked at a faster cooking rate (p<0.05) or stored in vacuum packs (p<0.01). Significant two-way and three-way interactions were observed between the effects of muscle vitamin E level, cooking conditions and packaging on lipid oxidation. Adopting more than one of these approaches to minimize lipid oxidation was more effective than adopting a single approach.     

Prevention of Pinking, Off-odor, and Lipid Oxidation in Irradiated Pork Loin Using Double Packaging

ABSTRACT: Lipid oxidation, color, volatiles, and sensory evaluation of double-packaged pork loin were determined to establish a modified packaging method that can improve the quality of irradiated pork loins. Vacuum-packaged irradiated samples produced dimethyl sulfide and dimethyl disulfide responsible for irradiation off-odor, whereas lipid oxidation was promoted under aerobic conditions. Exposing double-packaged irradiated pork to aerobic conditions for 1 to 3 d was effective in controlling both lipid oxidation and irradiation off-odor, regardless of packaging sequence. Sensory panels could distinguish the decrease in irradiation off-odor intensities by modifying the packaging method. However, carbon monoxide heme pigments, responsible for the increased redness by irradiation, were not effectively controlled by double packaging alone.     

Factors in Various Fractions of Meat Homogenates That Affect the Oxidative Stability of Raw Chicken Breast and Beef Loin

ABSTRACT:  The fractions of meat homogenates were analyzed to find the factors that determine the susceptibility of raw chicken breast and beef loin to lipid oxidation. The fractions used in this study were meat homogenate, precipitate, and supernatant of homogenate after centrifugation, and high and low molecular weight fractions from the supernatant. Chicken breast showed greater oxidative stability than beef loin during 10-d storage ( P < 0.05). All fractions from chicken breast showed lower amounts of free ionic iron and myoglobin and higher total antioxidant capacity (TAC) than those from beef loin during storage. The TAC level of chicken breast maintained during storage. This suggested that the oxidative stability of chicken breast was ascribed to high, stable total antioxidant capacity with low level of catalysts for lipid oxidation. The water-soluble high molecular weight fraction, which contained myoglobin, was responsible for the high lipoxygenase-like activity and lipid oxidation potential (LOP) in beef loin. TAC in all fractions from beef loin decreased during storage. This suggested that high myoglobin content in beef loin caused the imbalance between pro- and antioxidant factors leading to the high susceptibility of beef loin to lipid oxidation. Myoglobin served a major source of catalysts, ferrylmyoglobin, hematin, and/or free ionic iron, for lipid oxidation.     

Volatiles Production and Lipid Oxidation in Irradiated Cooked Sausage as Related to Packaging and Storage

Irradiation dose affected production of volatiles in vacuum-and aerobic-packaged cooked pork sausage, but its effect on TBARS was minor. Storage increased production of volatiles and changed their composition only in aerobic-packaged sausage. Among volatile components, 1-heptene and 1-nonene were influenced most by irradiation dose, and aldehydes by packaging type. TBARS and volatiles of vacuum-packaged irradiated cooked sausage did not correlate well. However, TBARS had very high correlation with amount of aldehydes, total volatiles, ketones and alcohols with long retention times in aerobic-packaged pork sausage. Heptene and 1-nonene could be indicators for irradiation; and propanal, pentanal, and hexanal for oxygen-dependent changes of cooked meat.     

Packaging Cooked Turkey Meat Patties while Hot Reduces Lipid Oxidation

Elimination of oxygen by “hot packaging” reduced the 2-thiobarbituric acid reactive substances (TBARS) value of meat patties by about 50% in control and myoglobin added, and between 30-40% in ferrous iron added turkey patties, as compared with “cold packaging.” The TBARS values of hot and cold vacuum packaged patties were significantly lower than those of loosely packaged patties after 1 wk refrigerated storage. Most lipid oxidation in meat patties occurred at day 0, and only small changes in TBARS values were observed after 1 wk storage. Although the prooxidants in meat were major factors in promotion of lipid oxidation of cooked meat, hot packaging minimized their effects.     

猪五花肉红烧过程中脂肪和脂肪酸的变化规律

目的：探讨以猪五花肉为原料的红烧肉加工过程中脂肪和脂肪酸的变化,以期对红烧肉的风味、营养、质地等研究提供参考。方法：对红烧肉加工过程中原料、油炸、炖煮过程样品（0～2 h,每30 min取样）以及成品的粗脂肪含量、过氧化值（peroxide value,POV）、硫代巴比妥酸（thiobarbituric acid reactive substances,TBARS）值以及脂肪酸含量进行测定。结果：五花肉红烧过程中脂肪含量显著下降（P＜0.05）,成品红烧肉脂肪含量比原料肉下降12.14%;POV先增大后减小,在炖煮30 min达到最大值;TBARS值逐渐增大,在炖煮过程中变化显著（P＜0.05）;油酸、棕榈酸、亚油酸和硬脂酸是五花肉脂肪中的主要脂肪酸,在红烧过程中饱和脂肪酸（saturatedfatty acid,SFA）含量变化不大（P＞0.05）,单不饱和脂肪酸（monounsaturated fatty acid,MUFA）含量显著上升（P＜0.05）,多不饱和脂肪酸（polyunsaturated fatty acid,PUFA）含量显著下降。结论：五花肉红烧过程中脂肪含量下降、脂肪发生适度氧化、脂肪酸组分构成发生了改变。     

Cholesterol and Lipid Oxidation Products in Cooked Meat as Affected by Raw-Meat Packaging and Irradiation and by Cooked-Meat Packaging and Storage Time

Aerobic packaging significantly increased cholesterol oxidation products (COPs) and thiobarbituric acid reactive substances (TBARS) in cooked turkey, pork, and beef patties after 7‐d storage, but vacuum packaging was very effective in preventing cholesterol and lipid oxidation. Packaging of meat after cooking had a much stronger effect on COPs formation than before cooking, and irradiation had only a minor effect. The amount of total COPs correlated well with TBARS in cooked meat. Turkey had the highest rates of COPs and TBARS formation and beef had the lowest rates after 7‐d storage, which were closely related to the fatty acid composition of meats. 7a‐hydroxycholesterol, 7p‐hydroxycholesterol, and 7‐ketocholesterol were the major COPs detected in all 3 cooked meat patties.     

Oxygen Availability Affects Prooxidant Catalyzed Lipid Oxidation of Cooked Turkey Patties

The catalytic effect of free ionic iron, hemoglobin and/or NaCI, and the effect of total lipid, class of lipid, and fatty acid composition on lipid oxidation of precooked refrigerated meat patties were highly significant only when oxygen was freely accessible to the patties during storage. With limited oxygen contact (cold vacuum-packaging) after cooking, the 2-thiobarbituric acid reactive substances (TBARS) values of patties were much lower than the values for patties with free oxygen contact (loose packaging) and did not increase substantially during storage. However, the TBARS values of cold packaged patties were higher (P<0.05) than those of hot packaged patties which had almost no oxygen contact after cooking. Elimination of oxygen during storage (hot or cold vacuum-packaging after cooking) resulted in prooxidants, fat content, fatty acid composition or the class of lipids having no effect on lipid oxidation.     

Front Face Fluorescence Spectroscopy—A Rapid Method to Detect Early Lipid Oxidation in Freeze Stored Minced Turkey Meat

ABSTRACT:  The purpose of this study was to elucidate the ability of front face fluorescence spectroscopy to measure early lipid oxidation in minced turkey meat, and compare it to other methods for determination of oxidative status such as sensory analysis, dynamic headspace gas chromatography combined with a mass spectrometer (GC-MS), and thiobarbituric acid-reactive substances (TBARS) value. This comparison was performed on one batch of minced turkey meat. The meat was stored at −20 °C and −10 °C in vacuum or exposed to air. The results showed that fluorescence analysis is a sensitive, nondestructive method for measurement of early lipid oxidation, and its rapidity and ease of use facilitates it as a practical screening method in research as well as food production. The level of specific marker compounds for lipid oxidation (for example, 1-penten-3-ol) was highly correlated with the fluorescence data.     

冻融循环对熟制鲣鱼暗色肉脂质变化的影响

为探究冻融循环对熟制鲣鱼暗色肉脂质变化的影响,对熟制鲣鱼暗色肉进行冻融循环（0、2、4、6、8 次）贮藏,测定冻融过程中样品的过氧化值（peroxide value,POV）、酸价（acid value,AV）、pH值、脂质组成、脂肪酸组成等指标。结果显示,在冻融循环贮藏过程中,脂质组成发生明显变化,甘油三酯（triacylglycerol,TAG）和磷脂（polar lipid,PL）质量分数明显降低,游离脂肪酸（free fatty acid,FFA）质量分数明显升高。在冻融循环过程中暗色肉的pH值显著减小,POV和AV显著增加（P＜0.05）。脂质中总饱和脂肪酸和总多不饱和脂肪酸含量都逐渐下降,TAG和PL中脂肪酸含量明显下降,其中PL中总多不饱和脂肪酸含量下降明显,FFA中总多不饱和脂肪酸含量显著升高（P＜0.05）。主成分分析（principal component analysis,PCA）和偏最小二乘判别分析（partial least squares discriminant analysis,PLS-DA）结果表明,经过不同冻融次数的鱼肉之间存在一定的差异性,且随着冻融次数的增加脂质氧化程度不断加剧。相关性分析结果表明FFA质量分数与POV、AV呈正相关,与PL质量分数、TAG质量分数、pH值呈负相关。实验结果表明冻融循环会影响熟制鲣鱼暗色肉脂质组成,同时引起脂质的氧化分解。这为熟制鲣鱼暗色肉在运输和贮藏过程中脂质控制提供一定的理论指导。