Effect of cooking and storage on lipid oxidation and development of cholesterol oxidation products in water buffalo meat

Changes in the physicochemical properties of chilled and frozen-thawed lamb cuts subjected to pulsed electric field processing

There has been recent interest in the use of pulse electric field (PEF) processing of muscle foods to improve food quality. In this study, the effects of PEF processing and storage (0 and 7 days) on the physicochemical properties and sensory characteristics of different frozen thawed and chilled lamb meat cuts were investigated. Seven lamb cuts (knuckle, rump, topside, shoulder shank, loin and rib) were treated at electric field strengths of 1-1.4 kV.cm^-1, specific energy of 88-109 kJ.kg^-1, frequency of 90 Hz, pulse width of 20 µs, and pulse number of 964. PEF had less effects on cooking loss when applied to frozen-thawed meat compared to chilled meat samples. PEF treatment of all chilled cuts at 0 and 7 days storage significantly decreased fatty acids. PEF treated chilled topside, knuckle, rump anf loin cuts stored for 7 days resulted in significantly increased amino acids content. PEF treatment of almost all frozen lamb cuts (except rib cut) that were stored for 7 days significantly increased TBARS value, decreased fatty acids, and increased amino acids content.

Quantification of Cooking Method Effect on COP Content in Meat Types Using Triple Quadrupole GC-MS/MS

A diet containing cholesterol is an essential component of biological function; however, cholesterol oxidation products (COPs) remain a major public health concern. This study investigated the effects of cooking methods (boiling and frying) on the production levels of COPs in processed foods. Samples, as represented by minced beef, chicken sausages, and fish fillets, were subjected to different cooking methods followed by COP extraction using a saponification method. Then, six common COPs, 5α-cholest, α-epoxy, β-epoxy, 25-HC, triol, and 7-keto, were quantified by triple quadrupole gas chromatography-mass spectrometry (GS-MS/MS). A significantly high number of COPs were detected in minced meat, of which 7-keto and triol were detected as major oxidation products, followed by chicken sausages and fish fillets (p ≤ 0.05). Compared to boiling, frying generated significantly more COPs, specifically triol (0.001-0.004 mg/kg) and 7-keto (0.001-0.200 mg/kg), in all samples. Interestingly, cholesterol level was found to be slightly (but not significantly) decreased in heat-treated samples due to oxidation during cooking, producing a higher number of COPs. Notably, the fish fillets were found to produce the fewest COPs due to the presence of a low amount of cholesterol and unsaturated fatty acids. In conclusion, adapting boiling as a way of cooking and choosing the right type of meat could serve to reduce COPs in processed foods.

Chemistry, biochemistry, metabolic fate and mechanism of action of 6-oxo-cholestan-3β,5α-diol (OCDO), a tumor promoter and cholesterol metabolite

Oxygenation products of cholesterol, named oxysterols, were suspected since the 20th century to be involved in carcinogenesis. Among the family of oxysterol molecules, cholesterol-5,6-epoxides (5,6-EC) retained the attention of scientists because they contain a putative alkylating epoxide group. However, studies failed into demonstrating that 5,6-EC were direct carcinogens and revealed a surprising chemical stability and unreactivity towards nucleophiles in standard conditions. Analyses of 5,6-EC metabolism in normal cells showed that they were extensively transformed into cholestane-3β,5α,6β-triol (CT) by the cholesterol-5,6-epoxide hydrolase (ChEH). Studies performed in cancer cells showed that CT was additionally metabolized into an oxysterol identified as the 6-oxo-cholestan-3β,5α-diol (OCDO), by the 11β-hydroxysteroid dehydrogenase of type 2 (HSD2), the enzyme which inactivates cortisol into cortisone. Importantly, OCDO was shown to display tumor promoter properties in breast cancers, by binding to the glucocorticoid receptor, and independently of their estrogen receptor status, revealing the existence of a new tumorigenic pathway centered on 5,6-EC. In breast tumors from patients, OCDO production as well as the expression of the enzymes involved in the pathway producing OCDO, namely ChEH subunits and HSD2, were higher compared to normal tissues, and overexpression of these enzymes correlate with a higher risk of patient death, indicating that this onco-metabolism is of major importance to breast cancer pathology. Herein, we will review the actual knowledge and the future trends in OCDO chemistry, biochemistry, metabolism and mechanism of action and will discuss the impact of OCDO discovery on new anticancer therapeutic strategies.

Lipids of pork meat as affected by various cooking techniques / Modificaciones de los lípidos de carne de cerdo en función de su guiso

The effects of different cooking techniques on the lipids of pork meat were evaluated. The assayed cooking techniques were deep-frying (DF), shallow-frying (SF), roasting (RO) and boiling (BO). Modi fication of the roasting meat due to reheating in a microwave oven after 24 h at 4 °C (MW), was also studied. In DF and SF significant increases were found in the lipid content (13.7 and 16.7 g/100 g of dry basis, respectively) and in the nun-polar lipids (11.2 and 14.2 g/100 g of dry basis, respectively) due to the absorption of the oil used in these cooking treatments. The main variations in the fatty acid composition of phospholipids and non-polar lipids were observed in the polyunsaturated fatty acid fraction. There was an increase in the content of free fatty acids (SFA, MUFA, PUFA) after MW, BO and RO. By contrast, free fatty acid content in DF and SF was similar to the content of initial raw meat. MW showed the greatest degradation of the phospholipid fraction, with a significant decline in phosphatidyl ethanolamine. All cooking treatments produced an increase in lipid oxidation, this be ing higher in RO and MW treatments.

Quality characteristics of fried lamb nuggets from low-value meat cuts: Effect of formulation and freezing storage

This study revealed the possibility of manufacturing prefried lamb nuggets from low-value cuts (flank) and evaluated the effect of formulation (50:50 vs. 20:80 of leg/flank cuts) and freezing (−20 ℃ for two months) on different quality parameters. Frying process produced a decrease of water content, an increase in lipid oxidation indicators, and an intense browning of nuggets surface. The use of flank up to a 75% of the total meat in the formula led to higher fat contents and higher polyunsaturated fatty acid proportions in fried nuggets. This made them more prone to get oxidized during the freezing storage and subsequent final frying. Nuggets with a higher proportion of flank also showed lower shear force values. However, nuggets with both formulations showed similar sensory acceptance. Freezing storage of lamb meat nuggets for two months increased the levels of lipid oxidation indicators, but again not to a level high enough to influence the sensory perception by consumers. So that, frozen nuggets from both formulations showed similar consumer acceptance to freshly produced ones with quite good scores (3.46–3.86 out of 5). Thus, low-value lamb cuts are suitable for being processed into highly acceptable prefried frozen lamb nuggets, which constitutes an opportunity for adding value to the whole lamb value chain.

In Vitro Effects of Cooking Methods on Digestibility of Lipids and Formation of Cholesterol Oxidation Products in Pork

This study investigated the effects of cooking methods on the digestibility of lipids and formation of cholesterol oxidation products (COPs) in pork, during in vitro human digestion. Pork patties were cooked using four different methods (oven cooking, pan frying, boiling, and microwaving), to an internal temperature of approximately 85℃. The digestibility of pork patties were then evaluated, using the in vitro human digestion model that simulated the composition (pH, minerals, surfaceactive components, and enzymes) of digestive juices in the human mouth, stomach, and small intestine. The total lipid digestibility was higher after microwave cooking, whereas pan-frying resulted in lower in vitro digestibility, compared to the other cooking methods. The microwaving method followed by in vitro digestion also showed significantly higher content of free fatty acids and thiobarbituric acid reactive substances (TBARS), compared to the other cooking methods; whereas, the pan frying and boiling methods showed the lowest. Cholesterol content was not significantly different among the cooked samples before, and after in vitro human digestion. The formation of COPs was significantly higher in the microwave-treated pork samples, compared to those cooked by the other methods, which was consistent with the trend for lipid peroxidation (TBARS). We propose that from the point of view of COPs formation and lipid oxidation, the pan-frying or boiling methods would be useful.

Carcass characteristics, composition, physico-chemical, microbial and sensory quality of emu meat

1. In order to investigate whether emu meat is a potential red meat alternative, this work was carried out with the objective of studying the carcass characteristics, proximate composition, physico-chemical and microbial characteristics and sensory attributes of emu meat. 2. Carcass characteristics clearly indicate that emus are a significant source of lean meat, fat, skin and edible by-products and these findings confirm earlier reports. 3. Proximate composition of emu meat indicated higher protein and ash content and lower fat, total lipids and cholesterol content than meat from other meat animals. 4. The pH, water holding capacity, collagen content and solubility, protein extractability, muscle fibre diameter and Warner-Bratzler shear force values of emu meat are similar to the earlier reports for meats from other food animals. 5. Emu meat is dark, cherry red in colour with significantly higher myoglobin content and the myoglobin is more prone to oxidation as evidenced by higher initial metmyoglobin percentage. The initial thiobarbituric acid reactive substances (TBARS) values and free fatty acids percentage in emu meat were higher than those in meats from other species. 6. Sensory evaluation of cooked emu meat curry revealed highly acceptable scores relative to goat meat curry, the most preferred meat in India. 7. The study shows the potential of emu meat as a new source of low fat, quality meat proteins. However, more studies are required to elucidate the effect of age, sex, muscles, pre-slaughter and post-slaughter factors on different carcass and meat quality characteristics.

Proximate and fatty acid composition and cholesterol content of different cuts of guinea fowl meat as affected by cooking method

BACKGROUND

Poultry is one of the leading meat products in South Africa, and its nutritional composition can be affected by the cut and cooking method. Limited food composition data are available for typical South African poultry products. This study investigated the effect of different cuts and cooking methods on the proximate and fatty acid composition as well as the cholesterol content of guinea fowl (Numida meleagris) meat.

RESULTS

The open-roasting method produced the highest moisture content for all cuts, and the baking bag method the lowest. The baking bag method resulted in the highest protein content. Cooking method had no effect on fat content, although breast had the lowest and thigh the highest fat content. Ash content was highest in the open-roasted drumstick. All cuts, regardless of cooking method, had a favourable polyunsaturated/saturated fatty acid (P/S) ratio (>0.4). Their n-6/n-3 ratio was also within the recommended beneficial range (<4:1). Both cooking method and cut affected cholesterol content.

CONCLUSION

Different cuts of guinea fowl vary in proximate and fatty acid composition as well as in cholesterol content, which in turn is affected to varying degrees by cooking method.

Effect of Different Packaging Methods and Storage Temperature on Microbiological and Physicochemical Quality Characteristics of Meatball

The objective of this research was to determine physicochemical changes and microbiological quality of the different packaged meatball samples. Meatball samples in polystyrene tray were closed with polyethylene film (PS packs), vacuumed and modified atmosphere packaged, (MAP) (65% N2, 35% CO2), and held under refrigerated display (4 °C) for 8, 16 and 16 days for PS packs, vacuum and MAP, respectively. Microbial load, free fatty acids and thiobarbituric acid values of the samples tended to increase with storage time. Bacteria counts of the raw meatball samples increased 2 log cycles at the end of storage compared with initial values. Meatball samples can be stored without any microbiological problem for 7 days at 4 °C. Results from this study suggested that shelf-life assigned to modified-MAP and vacuum-packed meatballs may be appropriate. Meatball samples underwent physical deformation when they were packed before vacuum process. With these negative factors considered, MAP is superior to other two packs methods.

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.

Effect of meat cooking on physicochemical state and in vitro digestibility of myofibrillar proteins

The effect of meat cooking was measured on myofibrillar proteins from bovine M. Rectus abdominis. The heating treatment involved two temperatures (100 degrees C during 5, 15, 30, and 45 min and 270 degrees C during 1 min). Protein oxidation induced by cooking was evaluated by the level of carbonyl and free thiol groups. Structural modifications of proteins were assessed by the measurement of their surface hydrophobicity and by their aggregation state. With the aim of evaluating the impact of heat treatment on the digestive process, myofibrillar proteins were then exposed to proteases of the digestive tract (pepsin, trypsin, and alpha-chymotrypsin) in conditions of pH and temperature that simulate stomach and duodenal digestion. Meat cooking affected myofibrillar protein susceptibility to proteases, with increased or decreased rates, depending on the nature of the protease and the time/temperature parameters. Results showed a direct and quantitative relationship between protein carbonylation (p<0.01) and aggregation (p<0.05) induced by cooking and proteolytic susceptibility to pepsin. However, no such correlations have been observed with trypsin and alpha-chymotrypsin.

Effects of Various Fat Sources, α-Tocopheryl Acetate, and Ascorbic Acid Supplements on Fatty Acid Composition and α-Tocopherol Content in Raw and Vacuum-Packed, Cooked Dark Chicken Meat

A factorial design was used to study the effects of dietary fat sources (beef tallow, fresh and oxidized sunflower oils, and linseed oil), alpha-tocopheryl acetate (0 and 225 mg/kg), and ascorbic acid (0 and 110 mg/ kg) supplementation on fatty acid composition, as well as on fat and alpha-tocopherol content in vacuum-packed raw and cooked meat stored at -20 degrees C. Raw meat fatty acid composition was affected by dietary fat sources and tocopheryl acetate supplementation. After cooking, meat composition was only affected by dietary fat sources. Birds fed linseed oil yielded meat rich in n-3 fatty acids, especially linolenic acid, which provides about 20% of the adequate intake for this fatty acid. Birds fed sunflower or oxidized sunflower oil produced meat rich in n-6 fatty acids, whereas those fed beef tallow resulted in meat rich in saturated and monounsaturated fatty acids. Raw and cooked dark chicken meat alpha-tocopherol content was only affected by tocopherol supplementation. Supplementation with alpha-tocopheryl acetate led to alpha-tocopherol-enriched meat, which provides about 25% of the recommended dietary allowance. Moreover, this content in vacuum-packed samples was not modified even after 7 mo of storage at -20 degrees C.

Combined effect of cooking (grilling and roasting) and chilling storage (with and without air) on lipid and cholesterol oxidation in chicken breast

The oxidation of the lipid fraction and cholesterol in raw and cooked chicken breast samples stored for 0 and 6 days at 4 degrees C under aerobic conditions and in vacuum packaging was studied. The multivariate statistical analysis showed significant effects of both culinary process and storage conditions on the lipid and cholesterol oxidation process, with a significant interaction between the two variables. Aerobic storage increased thiobarbituric acid reactive substances (TBA) from 0.04 to 0.06 ppm for raw samples, from 0.21 to 1.20 ppm for grilled samples, and from 0.24 to 1.62 ppm for roasted samples. During vacuum storage, only roasted samples showed significant increases in TBA. Levels of total cholesterol oxidation products (COP) remained low (2.88 to 4.35 microg/g of lipid) for all raw samples. Cooking increased COP levels to 12.85 and 11.54 microg/ g of lipid for grilled and roasted samples, respectively. Total COP and all individual COP except for cholestanetriol were significantly correlated with TBA and the peroxide index. However, the most extensive effect was attributable to the aerobic storage of cooked samples, which led to COP levels of 92.35 and 88.60 microg/g of lipid in grilled and roasted samples, respectively. Vacuum packaging did not increase COP levels for cooked samples.

Oxidative stability of dark chicken meat through frozen storage: influence of dietary fat and alpha-tocopherol and ascorbic acid supplementation

We used factorial design to ascertain the influence of dietary fat source (linseed, sunflower and oxidized sunflower oils, and beef tallow) and the dietary supplementation with alpha-tocopheryl acetate (alpha-TA) (225 mg/kg of feed) and ascorbic acid (AA) (110 mg/kg) on dark chicken meat oxidation (lipid hydroperoxide and TBA values and cholesterol oxidation product content). alpha-TA greatly protected ground and vacuum-packaged raw or cooked meat from fatty acid and cholesterol oxidation after 0, 3.5, or 7 mo of storage at -20 C. In contrast, AA provided no protection, and no synergism between alpha-TA and AA was observed. Polyunsaturated fatty acid-enriched diets (those containing linseed, sunflower, or oxidized sunflower oils) increased meat susceptibility to oxidation. Cooking always involved more oxidation, especially in samples from linseed oil diets. The values of all the oxidative parameters showed a highly significant negative correlation with the alpha-tocopherol content of meat.