Influence of carcass weight on instrumental and sensory lamb meat quality in intensive production systems

The effects of cooking viz. pressure-cooking and broiling and storage at 4 °C for six days and -10 °C for 90 days on lipid oxidation and development of cholesterol oxidation products in mutton were studied. Results revealed that cooking of meat significantly increased the total lipids, phospholipids, cholesterol, glycolipids, free fatty acids and glycerides, but they did not change during refrigerated and frozen storage. The TBA values increased on cooking and during storage. However, the values were below the threshold level for rancidity development. The following cholesterol oxidation products were separated by thin layer chromatography cholestanetriol, 7-α-hydroxy cholesterol, 19-hydroxycholesterol, 7-ketocholesterol, cholesterol-α-epoxide, cholesterol-β-epoxide and an unidentified fraction. All these fractions except the unidentified fraction increased on cooking. On refrigerated and even on frozen storage all these fractions increased except the unidentified fraction, which showed a concomitant reduction. The changes in broiled meat were more pronounced compared to pressure-cooked meat. Results clearly indicated that even frozen storage of cooked meat did not prevent the development of cholesterol oxidation products.     

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.     

Effect of irradiation and packaging conditions after cooking on the formation of cholesterol and lipid oxidation products in meats during storage

The effect of irradiation and packaging conditions on the content of cholesterol oxidation products (COPs) and lipid oxidation in cooked turkey, beef, and pork during storage was studied. Ground turkey leg, beef, and pork were cooked, packaged either in oxygen-permeable or oxygen-impermeable bags, and irradiated at 0 or 4.5 kGy. Lipid oxidation and COPs were determined after 0 and 7 days of storage at 4°C. Packaging of cooked meat was more important than irradiation in developing COPs and lipid oxidation in cooked meats during storage. 7-Hydroxycholesterol, 7β-hydroxycholesterol, β-epoxide, and 7-ketocholesterol were among the major COPs formed in cooked turkey, beef, and pork after storage, and their amounts increased dramatically during the 7-day storage in aerobic conditions. Irradiation had no significant effect on the amounts of any of the COPs found in cooked turkey and beef, but increased (P<0.05) the amounts of - plus 7β-hydroxycholesterol, β-epoxide, 7-ketocholesterol, and total COPs in aerobically packaged cooked pork. The amounts of COPs and lipid oxidation products (TBARS) closely related to the proportion of polyunsaturated fatty acids in meat. The results indicated that the composition of fats in meat is important on the oxidation rates of lipids and cholesterol, and packaging is far more important than irradiation in the formation of COPs and lipid oxidation in cooked meat.     

Wide-Bore Capillary Gas Chromatographic Method for Quantification of Cholesterol Oxidation Products in Egg Yolk Powder

A wide-bore capillary gas chromatographic (GC) method was developed for quantification of cholesterol oxidation products in egg yolk powder. Baseline separations were achieved between 7α- and 7β-hydroxycholesterol, cholesterol, cholesterol-5α,6α-epoxide, cholesterol-5β,6β-epoxide and 7-ketocholesterol chromatographed as the trimethylsilylated sterols. Excellent response linearity was obtained for each cholesterol oxidation product, permitting reliable quantification. Recoveries from freeze-dried egg yolk spiked with various levels of cholesterol oxidation products ranged from 78.2 to 95.1%. The coefficients of variation compared favorably to those for packed column GC methods.     

Enzymatic Determination of Cholesterol Oxides

For measurement of the concentration of oxidised cholesterols in foodstuffs, a method was developed by adapting the well-known enzymatic determination of cholesterol. A linear correlation was found between the absorbance measured after enzymatic reaction and the concentrations of 7α-hydroxycholesterol, 7β-hydroxycholesterol, 7-ketocholesterol, cholesterol-5α, 6α-epoxide in the range 1–12 μg. The usefulness of this method was demonstrated by determination of the four cholesterol oxidation products separated by TLC from the non-saponifiable lipid fraction of 5-month-old whole-egg powder (stored under different conditions) and of biscuit enriched with egg powder. The main advantages of the combination of TLC and the enzymatic method, beyond its rapidity and sensitivity, are that the determination of cholesterol oxidation products can be carried out in parallel with many samples containing small amounts of oxidised cholesterols even in the presence of a large quantity of cholesterol.     

Evaluation of cholesterol and lipid oxidation in raw and cooked minced beef stored under oxygen-enriched atmosphere

Oxygen-enriched modified atmosphere packaging (MAP) represents an important means to stabilize meat colour but may lead to an increase in lipid oxidation, influencing the acceptability and safety of the product. In this work, the effect on cholesterol and lipid susceptibility to oxidation was investigated in commercial minced beef held under MAP (80% O(2)/20% CO(2)). Cholesterol oxidation products (COPs), peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were determined, before and after pan frying, at 1, 8 and 15 days since packaging under refrigerated storage (3-4°C). 7α-Hydroxycholesterol, 7β-hydroxycholesterol and 7-ketocholesterol were the more abundant COPs identified. COPs significantly increased in raw beef during storage: after 1, 8 and 15 days since packaging COPs were at the levels of 10.4, 30.7 and 60.5μg/g of fat, respectively. Cooking did not affect cholesterol oxidation in freshly packaged minced beef but led to a rise in COPs amount with respect to raw muscle after 8 and 15 days of storage. The trend in cholesterol oxidation reflected the progressive increase in lipid peroxidation rate brought by MAP conditions.     

Cholesterol Oxidation Products in Some Muscle Foods

Cholesterol oxidation products were estimated in some meat products by capillary gas chromatography after trimethylsilylation. Peak identities were confirmed by mass spectrometry. Freeze-dried pork, stored in contact with air at 22°C for ca. 3 yr, revealed 7α- and 7β-hydroxycholesterol, 7-ketocholesterol, α- and β-epoxide and cholestane-triol. The total concentration of oxidation products reached almost half of the remaining cholesterol content with 7-ketocholesterol as the predominant species. Some oxidation products were noted at a few ppm levels in broiled beef steaks, but not in precooked beef products. As rancidity development advanced in comminuted and cooked meats during storage, the oxidation of cholesterol became apparent.     

Effect of different cooking methods on lipid oxidation and formation of free cholesterol oxidation products (COPs) in Latissimus dorsi muscle of Iberian pigs

The aim of this work was to study the influence of different cooking methods (grilled (GR), fried (FP), microwave (MW) and roasted (RO)) on lipid oxidation and formation of free cholesterol oxidation products (COPs) of meat from Iberian pigs that have been fed on an intensive system. Moisture and total lipid content, TBARs, hexanal and COPs were measured in Latissimus dorsi muscle samples. Cooking did not produce changes in total lipid content in meat but induced significantly higher lipid oxidation (TBARs and hexanal values) (p < 0.001) and cholesterol oxidation (COPs) (p < 0.01). When the different cooking methods were studied, the grilled method was the least affected by lipid oxidation (TBARs and hexanal) compared to the others. There were no significant differences among different cooking methods on COPs values. The most abundant cholesterol oxides were both 7α-hydroxycholesterol and 7β-hydroxycholesterol in all groups studied.     

Culinary herbs inhibit lipid oxidation in raw and cooked minced meat patties during storage

The effect of dried spices and the ethanol extract of those spices was studied on the stability of fresh chicken minced meat, and fresh and cooked pork patties pretreated with NaCl during refrigerated and frozen storage. The antioxidant activities of the spices were measured by thiobarbituric acid reactive substances (TBARS) and peroxide value (POV) in meat samples. The lipid oxidation was effectively inhibited in the chicken meat treated with several dry spices diminishing the TBARS to a range of 32% and 83% of those found in the control samples in frozen stored meat for 6 months. Marjoram, wild marjoram and caraway were the most effective dry spices. Ethanolic extracts of the same spices were more potent as antioxidants by lowering the concentration of the TBARS to a range of 20–27% of those found in the control samples. Addition of sodium salt to the minced pork resulted very high concentrations of the oxidation products originated from the polyunsaturated fatty acids. The treatment with ethanolic extract of spices (sage, basil, thyme and ginger) significantly inhibited the lipid peroxidation in refrigerated and chilled pork patties pretreated with NaCl by reducing both POV and TBARS. Heat treatment with microwaves produced significantly elevated levels of both lipid peroxides and TBARS, but the amount of these oxidation products was less than 10% in spice‐treated salted meat samples compared to that in untreated ones. Lipid peroxidation also grew continuously during the storage period at −18°C in raw and cooked samples. Ethanolic extracts of spices had a very strong antioxidative effect inhibiting lipid peroxidation in heat‐treated meat products during frozen storage. The highest antioxidant activity was observed in the case of ginger. High correlation coefficients were found between TBARS and POV both in raw and cooked pork patties (0.86, 0.91, respectively) during frozen storage. It is supposed that these compounds originated from the polyunsaturated fatty acids during oxidation processes but at different stages. Utilization of spices, spice mixtures or spice extracts in semi‐prepared meat products intended to be frozen for up to 6 months or more before consumption is proved to be advantageous in regard of shelf life of the food, as well as of human health, because of the beneficial effect of spices in inhibition of lipid peroxidation during heat treatment and chilling storage. © 1999 Society of Chemical Industry     

Effect of processing and storage on neutral lipids of buffalo meat

Three muscles viz. Triceps brachii (TB), Longissimus dorsi (LD) and Biceps femoris (BF) from different anatomical locations of adult male buffaloes were stored after broiling and pressure cooking under refrigerated (4°C) condition for 3, 6, 9 days and 30, 60, 90 days under frozen (-10°C) storage. At the end of each storage interval they were analysed for total lipids, cholesterol contents and glyceride fractions i.e. monoglycerides (MG), diglycerides (DG), and triglycerides (TG). Muscles differed significantly in total lipids as well as contents of all glyceride fractions. Muscle LD had significantly higher total lipid content than TB and BF. Muscles differed significantly in their esterfied cholesterol (EC) contents. Heat processing increased total lipids, cholesterol, MG, DG and TG contents of all the buffalo muscles studied. Total cholesterol contents remained unchanged during refrigerated and frozen storage. However, EC, MG, DG and TG contents declined during storage. The influence of anatomical locations on fatty acid composition of neutral lipids was observed. The ratio of unsaturated to saturated fatty acids increased due to cooking. A gradual decrease in mono- and polyunsaturated fatty acids was recorded during refrigerated and frozen storage.     

Antioxidant Inhibition of Cholesterol Oxidation in a Spray-Dried Food System during Accelerated Storage

Spray-dried egg yolk was used to evaluate antioxidant inhibition of cholesterol oxidation during accelerated (CU⁺² and heat) storage. Liquid yolk was treated with equimolar amounts of BHA (0.01%, w/w of lipid), ascorbyl palmitate (0.023%), or a tocopherol blend (0.023%). Yolk batches were spray-dried, stored at 60 ± 2°C for up to 28 days, and analyzed for cholesterol oxidation products (COPS) using gas chroma-tography. COP levels generally increased during storage with 7-ketocholesterol predominant. Significant antioxidant effects were manifest in decreased levels of 7-ketocholesterol, 7α- and 7β-hydroxycholesterol; while cholestane-triol and cholesterol-5,6-epoxide levels were not affected. All antioxidants showed significant inhibitive effects relative to the control, and tocopherols were more effective than ascorbyl palmitate.     

Lipid and cholesterol oxidation in Chinese-style sausage using vacuum and modified atmosphere packaging

The oxidation of lipid and cholesterol in Chinese-style sausage in vacuum packaging (VP) and modified atmosphere packaging (MAP) stored at 4°C and 15°C, respectively, for 5 months was investigated. The 2-thiobarbitaric acid reactive substance (TBARS) and peroxide value (POV) of sausage were variable with packaging treatments during storage. TBARS and POV in sausage stored at 15°C were significantly greater (p < 0·05) than at 4°C, and the MAP treatment was more stable than the VP treatment. In addition, the polyunsaturated fatty acids (PUFA) in sausage decreased with storage for both treatments. The content of cholesterol decreased significantly after 3 months of storage. 7-β-hydroxycholesterol, 7-ketocholesterol and 22-ketocholesterol were the major cholesterol oxidation products (COPs), but there was no detectable (< 1 μg/100 g) 25-hydroxycholesterol or cholestanetriol with either treatment.     

Effect of natural antioxidant combinations on lipid oxidation in cooked chicken meat during refrigerated storage

The effect of combinations of sage, oregano and honey on lipid oxidation in cooked chicken meat during refrigeration at 4°C for 96h was determined. Chicken samples (thigh and breast) were then separated into five groups: control; butylated hydroxytoluene; oregano+sage; oregano+sage+5%honey and oregano+sage+10%honey. Quantitative measurements of thiobarbituric acid reactive substances, conjugated dienes, hexanal, fatty acids, cholesterol and cholesterol oxides were used as indicators of lipid oxidation. Acceptability and preference were also evaluated. The effectiveness of the natural antioxidants for reducing the velocity of lipid oxidation in cooked chicken thigh and breast was demonstrated after 48 and 96h of refrigeration at 4°C. The treatments that presented the lowest hexanal values after 96h of refrigeration were oregano+sage+5%honey and oregano+sage+10%honey. Only traces of free cholesterol oxides were found (25-OH, 7-k, 7α-OH and 7β-OH). The natural antioxidants protected cooked chicken meat from oxidation processes and resulted in great acceptability.     

Changes in phospholipids of buffalo meat during processing and storage

Effect of broiling and pressure cooking as well as alterations during refrigerated (4°C) and frozen (-10°C) storage on the phospholipids of adult male buffalo muscles viz. Triceps brachii (TB), Longissimus dorsi (LD) and Biceps femoris (BF), i.e. from three different locations were studied. Muscles differed significatly in their total lipid and phospholipid content. Cooking methods significantly altered the total phospholipid content and its fractions. Storage period did not show any significant effect on total phospholipids during refrigerated and frozen storage, whereas certain phospholipid classes viz. lysophosphatidyl choline and lysophosphatidyl ethanolamine + sphingomyelin increased significantly and major phospholipid classes viz. phosphatidyl choline and phosphatidyl ethanolamine decreased significantly. The changes in phospholipid classes were similar both in refrigerated and frozen samples but relatively more pronounced in the former. Palmitic, stearic, oleic and linoleic acids were the four predominant fatty acids in the phospholipids of buffalo meat. The effects associated with the location of muscles were evident. Differences in fatty acid composition of individual muscles in response to heat processing were observed. Heat processing significantly increased the total saturates in TB and LD muscles while it decreased in BF. The total monounsaturated and total polyunsaturated fatty acids of phospholipids decreased during refrigerated and frozen storage indicated by a significant decreass in oleic, linoleic and arachidonic acids.     

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.     

High-Resolution NMR Detection of Cholesterol Oxides in Spray-Dried Egg Yolk

A new approach, alternative to currently available methods, for studying cholesterol oxidation in egg powder is reported. The quantitative analysis of cholesterol oxides was carried out by high-resolution proton nuclear magnetic resonance (¹H-NMR). The following oxides were isolated from spray-dried egg powder by rapid chromatographic procedures and detected by selecting “marker”¹H-NMR signals: 7-ke-tocholesterol, 7α-hydroxy-cholesterol, 7β-hydroxy-cholesterol, cholesterol-α-epoxide and cholesterol-β-epoxide. The quantified cholesterol derivatives ranged from 4.9 to 9.1 ppm with a detection limit of 0.3 ppm (5 μ.g from 16g of matrix). The main usefulness of the method should be in investigating intermediates and products due to chemical transformation of cholesterol during storage and heating of foodstuffs.     

Effects of Frozen Storage and Cooking on Lipid Oxidation in Chicken Meat

Fresh chicken breast and leg meat samples, which were frozen for 3 months or 6 months at −18°C, were cooked in microwave and convection ovens and then tested for levels of lipid oxidation. After 6 months storage, malonaldehyde in fat from meat samples, as measured by a TBA assay, modified to avoid sample autoxidation, increased 2.5 fold, while the fluorescence excitation (360 nm) and emission (440 nm) spectra increased an average of 34%. Fat from meat cooked in a convection oven averaged 83% higher malonaldehyde concentration and 21% higher fluorescence compared to levels before cooking. Levels of lipid oxidation products in fat from chicken breast and leg meat were not significantly different in microwave compared to convection oven cooking; but certain secondary fluorescent products were higher in meats cooked by convection oven.     

Antioxidative activity of α-tocopherol in cooked and uncooked ground pork

The effect of α-tocopherol (0, 100, 200 ppm) on lipid oxidation either in cooked or uncooked ground pork was studied during aerobic storage at 4°C and -20°C. Lipid oxidation was measured using the 2-thiobarbituric acid (TBA) method and rancidity development was scored by a trained sensory panel. Alpha-tocopherol slowed the rate of oxidation in cooked ground pork stored at either 4°C or -20°C and uncooked samples refrigerated for extended periods of time (12 days). In cooked product stored at 4°C where oxidation development was intense and off-flavors were strong, panelists did not detect flavor differences due to treatments. But in cooked product stored at -20°C sensory results were consistent with TBA analysis. Pre-rigor grinding, known to induce a high pH and inhibit lipid oxidation in uncooked fresh pork, had no protective effect on lipid oxidation as measured by TBA values in cooked ground pork, regardless of storage condition. TBA numbers increased during storage of cooked product at 4°C with an increase in internal cooking temperature between 50°C and 80°C. Internal cooking temperatures of 70°C or higher induced a rapid rate of oxidation when stored at 4°C.     

Cholesterol and lipid oxidation in raw and pan‐fried minced beef stored under aerobic packaging

BACKGROUND: The type of packaging atmosphere has been reported as a technological factor that consistently affects the quality of lipid fraction in meat. Oxidation of cholesterol and lipids was evaluated before and after pan frying in commercial refrigerated minced beef stored under aerobic atmosphere for 1 and 8 days. RESULTS: In raw beef, cholesterol and lipid oxidation developed at a slow rate. Cholesterol oxidation products (COPs) did not significantly vary (～8 µg COPs g^?1 of fat) over 8 days, while in the same period thiobarbituric acid reactive substances (TBARS) less than doubled (from 0.7 to 1.2 malondialdehyde equivalents kg^?1 of muscle). Pan frying did not influence the oxidative degree in the fresh product but consistently catalyzed cholesterol oxidation in stored beef. A significant increase was assessed in beef at the end of storage: from 8.6 to 30.0 µg COPs g^?1 of fat in raw and cooked beef, respectively. CONCLUSION: Aerobic packaging did not appear as a pro‐oxidant factor in fresh minced beef with a good oxidative quality during a short period of refrigerated storage. Copyright © 2010 Society of Chemical Industry     

Lipid and cholesterol oxidation in frozen stored pork, salame Milano and mortadella

An investigation has been carried out on oxidative processes of fresh and stored frozen pork and of two pork products (salame Milano and mortadella). Wholesale pork cuts (shoulder, ham trimmings, belly and backfat) were checked fresh and after frozen storage (1, 3 and 6 months). The streaky bacon was studied fresh and after scalding at 80 °C. Salame Milano and mortadella were produced with fresh and frozen raw materials and a few commercial samples were also part of the study. No real differences have been observed between commercial and experimentally produced salame and mortadella. Peroxide and TBARS values were low in all cases. Among the cholesterol oxides determined (7β-hydroxycholesterol, 5,6α-epoxycholesterol, 7-ketocholesterol and 25-hydroxycholesterol) those dangerous for human health were either absent or their concentration was below toxic levels. The results are discussed on the light of literature reports and Italian pork products technologies.