Cholesterol oxidation in muscle tissue

Three model systems were designed to monitor the oxidative stability of cholesterol in different lipid environments. The cholesterol moiety of cholesteryl linoleate oxidized to a greater extent than that of cholesteryl stearate and free cholesterol. Cholesterol oxidized when dispersed with either phosphatidyl choline or adipose tissue, further demonstrating that cholesterol oxidation is affected by the surrounding lipid environment.

Oxidation of cholesterol in muscle tissue was also affected by the membrane environment. Vitamin E supplementation of veal calves improved the oxidative stability of muscle lipids and cholesterol. Comparison was made of the oxidative stability of retail beef lipids, including cholesterol, with the oxidative stability of veal lipids and cholesterol. The results supported the hypothesis that if initiation of lipid oxidation occurs in the muscle membranes, the fat content of the meat should not influence the stability of the lipids to initial oxidation.     

Antioxidant properties of differently processed spinach products

The effect of variously processed spinach products (whole-leaf, minced and enzymatically liquefied spinach) on lipid oxidation was determined. In an autoxidative methyl linoleate (MeLo) system the inhibition of hydroperoxide formation, measured by HPLC after three days of oxidation, was in descending order: whole-leaf > liquefied > minced spinach. The inhibition of formation of thiobarbituric acid-reactive substances (TBARS) and hexanal by spinach was determined in cooked meatballs with added spinach after two days of storage at 4 degrees C. The formation of TBARS was inhibited by liquefied spinach at 200 g/kg meat; all other spinach products tested at 100 and 200 g/kg were pro-oxidative. The formation of hexanal was inhibited by both minced and liquefied spinach at 100 and 200 g/kg meat. The variously processed spinach products behaved differently when tested for their antioxidant activity (MeLo) or oxidative stability (meatballs). We conclude that the effect of spinach products on lipid oxidation is affected by processing.     

Effects of conjugated linoleic acid on the degradation and oxidation stability of model lipids during heating and illumination

The effects of methyl conjugated linoleate (MCLA) on the degradation and oxidative stability of model lipids, methyl linoleate (ML), methyl oleate (MO) and methyl stearate (MS), during heating at 100, 150 or 200°C for 3 h or illumination at 4000 lux for 14 days were studied. Results showed that under either temperature treatment or illumination, MCLA was the most susceptible to degradation, followed by ML, MO and MS. At 100°C, peroxide formation was the main reaction in each model lipid. However, at 150°C, peroxide formation was the main reaction in the initial period of heating, followed by degradation. At 200°C, the degradation was the major reaction. In contrast, peroxide formation was the main reaction for each model lipid during illumination. The addition of MCLA may slow degradation of each model lipid during heating. However, the oxidation stability of the whole system (model lipid plus MCLA) may also be decreased. Under light storage, the effect of MCLA was insignificant.     

Extracts of plant cell cultures of <Emphasis Type="Italic">Lavandula vera</Emphasis> and <Emphasis Type="Italic">Rosa damascena</Emphasis> as sources of phenolic antioxidants for use in foods

Ethanolic extracts of plant cell cultures of lavender (Lavandula vera) and rose (Rosa damascena) have been examined as potential food antioxidants. The L. vera cell extract quenched the radicals Fremy’s salt, DPPH (2,2-diphenyl-1-picrylhydrazyl radical), and ABTS^·+ (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic) radical) more efficiently than the R. damascena extract. Also the L. vera extract inhibited lipid oxidation in a methyl linoleate emulsion more efficiently than the R. damascena extract. However, the L. vera extract had a prooxidative effect on the iron-based Fenton reaction in an aqueous model system. A similar effect was observed for pure rosmarinic acid, but not for the R. damascena extract. The addition of L. vera extract to minced chicken meat reduced lipid oxidation (measured as thiobarbituric acid reactive species) and the loss of α-tocopherol during cold storage after the meat was cooked. This suggests the antioxidative properties of L. vera extracts dominate in a real food system.     

Pro- and antioxidative activity of protein fractions from pork (longissimus dorsi)

Protein fractions from pork (longissimus dorsi), isolated in search of the factor in meat enhancing non-heme iron absorption, have been analysed for their effect on radical formation and oxidation processes. In heat-treated minced meat samples with the protein fractions incorporated, the water-soluble proteins showed a prooxidative effect on lipid oxidation compared to the salt-soluble and the insoluble proteins, which did not influence oxidation in the meat system relative to control samples. The level of secondary oxidation products in meat samples with water-soluble proteins added was, however, not as high as would be expected from the ability of this protein fraction to initiate oxidation as measured by spin-trapping ESR-spectroscopy in meat emulsions and by oxygen depletion rates in a lipid model system with the protein fraction added. In agreement with this observation, the water-soluble protein fraction was found, in addition to being prooxidative, also to have the highest antioxidative potential of the three protein fractions as measured by spin probing ESR-spectroscopy (Fremy's salt method). The prooxidative activity of the water-soluble proteins was assigned to myoglobin and hemoglobin derivatives (detected spectrophotometrically), emphasising the role of iron-catalysis in oxidative deterioration of meat products.     

Mechanisms of Oxidative Processes in Meat and Toxicity Induced by Postprandial Degradation Products: A Review

Antioxidant system loss after slaughtering, reactive species production, cell disruption, contact with oxygen and light, heme and nonheme iron, and irradiation starts up mainly by 2 related oxidative processes: lipid peroxidation and protein oxidation. Products generated in these processes are responsible for meat quality loss, and some of them are suspected to be toxic to humans. This review article is focused on reactive species implicated in oxidative processes in meat, on lipid peroxidation mechanisms, heme protein, and nonheme protein oxidation, and on some toxic oxidation and digestion products. Nonenzymatic fatty acid peroxidation is exemplified by an arachidonic acyl group, and the initiation of chain reaction can be described by 3 pathways: singlet oxygen, hydroxyl radical from the Fenton reaction, and perferrylmyoglobin. Enzymatic oxidation of fatty acids is exemplified using linoleic acid, and the main characteristics of lipoxygenase are also presented. Heme protein oxidation is described in an interrelation with lipid peroxidation and the significance for food quality is shown. For protein oxidation, 3 different mechanism types are described: oxidation of amino acid residues, oxidation of protein backbone, and reactions of proteins with carbonyl compounds from lipid peroxidation. The effects of oxidative damage on protein properties and bioavailability are also shown. At the end of each oxidative process, the postprandial toxicity induced by oxidation products and the dietary degradation products are presented. Also discussed are reports by some researchers who suggest that dietary lipid and protein oxidation products and heme iron from red meat are in part cytotoxic and/or genotoxic.     

Effects of pork meat cut and packaging type on lipid oxidation and oxidative products during refrigerated storage (8 degrees C)

ABSTRACT:  Lipid oxidation and oxidative products as affected by pork meat cut, packaging method, and storage time were evaluated during refrigerated storage. Pork belly had higher pH and thiobarbituric acid reactive substance (TBARS) values than pork loin, and aerobic-packaged belly had higher TBARS than vacuum-packaged counterparts. Loin had higher free fatty acid (FFA) values than belly, and increased FFA values were observed with increased storage time. Peroxide values increased up to 7 d and decreased thereafter. Volatile compounds such as alkanes, aldehydes, ketones, and alcohols with high volatility in belly were higher than those in loin. Nonanoic acid, ethyl ester in belly, and hexadecanoic acid in loin might be considered as indices of lipid oxidation. Overall, vacuum packaging was better than aerobic packaging to retard lipid oxidation and production of oxidative products, and loin was more sensitive to lipid oxidation than belly.     

Grape seed extract as antioxidant in cooked, cold stored turkey meat

Efficiency of four concentrations of grape seed extract (0.0, 0.4, 0.8, and 1.6 g/kg) in retarding oxidative rancidity was tested with cooked turkey breast meat. Development in lipid oxidation during 13 days of refrigerated storage was evaluated by means of thiobarbituric acid-reactive substances (TBARS) and volatile compound formation. Hexanal, pentanal, octanal, 2-octenal, 1-octen-3-ol, 2-octen-1-ol, and 1-penten-3-ol showed high correlations (r>0.95) with TBARS values and could, therefore, serve as markers for the oxidation process in the cooked turkey breast meat. Supplementation of grape seed extract prior to cooking significantly improved oxidative stability of minced turkey meat during heat treatment and storage. The ability of grape seed extract to prevent lipid oxidation was concentration-dependent. Vacuum-packaging considerably improved oxidative stability of meat regardless of the low concentration of grape seed extract used. It appears that grape seed extract could be very effective in inhibiting lipid oxidation of cooked turkey meat during chill-storage.     

Commercial antioxidants control lipid oxidation in mechanically deboned turkey meat

Effects of commercial rosemary antioxidants on oxidative stability of mechanically deboned turkey meat (MDTM) compared with Trolox C (vitamin E), ascorbic acid (vitamin C) and control without antioxidant were investigated. Antioxidants were added to meat at three levels. Thiobarbituric acid (TBA) assay and dynamic headspace gas chromatography were used to assess the effects of commercial antioxidants on lipid stability of MDTM during 7 months of frozen storage. Increased levels of TBA-reactive substances (TBARS) and volatile carbonyl compounds were noticed in all meat samples during storage, however most distinctly in meat without antioxidants. Retarding effect of antioxidants on the development of oxidation depended on the level and type antioxidants. Trolox C-a water soluble, synthetic derivative of vitamin E possessed the greatest antioxidative activity reflected by the lowest values of TBARS and volatile compounds. Ascorbic acid was less efficient than Trolox C and Biolox HT-W (rosemary), but more potent than most rosemary extracts in suppressing lipid oxidation especially in the long term frozen storage MDTM. The DPPH() method confirmed that antioxidant activity depends on the concentration of active compounds present in the samples available to scavenge the free radicals formed during the storage period. Supplementation of MDTM with antioxidants could be an alternative method to prevent oxidative degradation of the meat during frozen storage when vacuum packaging is not practical.     

Comparison of lipid and protein oxidation,total iron content and fatty acid profile of conventional and organic pork

The aim of the research was to compare differences in lipid and protein oxidation, total iron content and fatty acid profile in pork loin obtained from organic and conventionally reared pigs. The samples of organic meat were taken from breeding certified by the polish certifying body according to the Council Regulation (EC) no 834/2007 on organic production and labelling of organic products. The meat samples were examined at the following times post‐mortem: 2, 4, 7 days. Measurements of lipid oxidation showed that the organic meat samples were characterised by lower TBARS values during whole storage period (0.78–0.81 mg kg^?1) compared with those of conventional system production (0.95–0.99 mg kg^?1). Results of protein oxidation measurements of the organic meat sample were significantly lower (0.43 nmol mg^?1 protein) at the beginning of experiment than those for the conventional meat sample (0.66 nmol mg^?1 protein). It was also indicated that the production system had no effect on iron content and myoglobin oxidation during storage. In conclusion, obtained results pointed out that the organic pig meat was characterised by higher lipid stability during the whole storage time compared with meat from conventional production system.     

Lipid Oxidation, Color, Volatiles, and Sensory Characteristics of Aerobically Packaged and Irradiated Pork with Different Ultimate pH

ABSTRACT: Irradiation and storage increased lipid oxidation of normal and pale-soft-exudative (PSE) muscles, whereas dark-firm-dry (DFD) muscle was very stable and resistant to oxidative changes. Irradiation increased redness regardless of pork-quality type, and the increases were proportional to irradiation dose. Irradiation increased the production of sulfur-containing volatiles, but not lipid oxidation products. The total volatiles produced in normal and PSE pork were higher than the DFD pork. Some volatiles produced in meat by irradiation evaporated during storage under aerobic packaging conditions. Nonirradiated normal and DFD pork had higher odor preference scores than the nonirradiated PSE, but irradiation reduced the preference scores of all 3 pork-quality types.     

Effects of Dietary Rape Seed Oil, Copper(II) Sulphate and Vitamin E on Drip Loss, Colour and Lipid Oxidation of Chilled Pork Chops Packed in Atmospheric Air or in a High Oxygen Atmosphere

The effect of addition of rapeseed oil (canola), CuSO(4) and vitamin E (all-rac-α-tocopheryl acetate) to pig diets on pork meat quality (lipid oxidation, colour and drip loss) was studied. Pigs were reared on ten different diets, either a control diet (no supplementation of rapeseed oil, CuSO(4) or vitamin E) or 6% rapeseed oil diets supplemented with CuSO(4) (0, 35 or 175mg/kg) and vitamin E (0, 100 or 200mg all-rac-α-tocopheryl acetate/kg). The natural content of vitamin E originating from feed ingredients amounted to 9-23mg vitamin E (α-tocopherol) per kg feed. Muscle vitamin E levels reflected the dietary intake and pigs fed the control diet had significantly lower levels than pigs fed rapeseed oil diets. The quality of fresh pork chops packed in air or in 80% O(2):20% CO(2) was followed during chill storage for 8 and 13 days, respectively. Colour, as measured by tristimulus colorimetry of pork chops packed in 80% oxygen atmosphere, was significantly improved with respect to redness when compared to chops packed in air, regardless of dietary treatment. The low vitamin E content in pigs fed the control feed significantly decreased a values and the oxidative stability of pork chops during chill storage compared to the other feeding groups. Packing of chops in a high-oxygen atmosphere increased lipid oxidation, especially in chops with low levels of vitamin E. Supplementation of rapeseed oil diets with 100 or 200mg vitamin E significantly decreased lipid oxidation of chill stored chops. Supplementation with CuSO(4) did not influence meat quality attributes (drip loss, colour stability and lipid oxidation) for any of the storage conditions.     

Early post-mortem sarcoplasmic proteome of porcine muscle related to lipid oxidation in aged and cooked meat

In order to identify specific markers of lipid oxidation generated in meat during refrigerated storage and cooking an analysis was conducted to investigate the relationships between the early post-mortem sarcoplasmic proteome, which contains the majority of enzymes involved in the oxidative process, and the level of lipid oxidation. This study was performed in Longissimus lumborum pig muscle. Proteome was analysed by 2-D electrophoresis in combination with liquid chromatography–tandem mass spectrometry (LC–MS/MS) and lipid oxidation was estimated by the TBA reactive substances (TBA-RS) measurement. Many markers of lipid oxidation were identified, but no single marker covered the oxidative process in its entirety. The role of five protein groups (albumin, redoxins, annexins, lipid transporters and enzymes of aerobic respiration), from which a link with lipid oxidation can be established, is discussed. This study, which completes a precedent work focused on protein oxidation, clearly demonstrates that a combination of several markers is needed to assess the sensitivity of meat to oxidation during both ageing and cooking.     

Fat content has a significant impact on protein oxidation occurred during frozen storage of beef patties

This study examined the relationship between protein and lipid oxidation and the impairment of water holding capacity (WHC), colour and texture after frozen storage (20 weeks/−18 °C) and subsequent processing (cooking, chilled storage) of beef patties with increasing fat content (3, 20 and 35%). Various manifestations of protein oxidation were found to occur during frozen storage and processing of patties including, loss of tryptophan fluorescence, carbonylation and formation of Schiff bases structures (SB). Patties with higher fat content underwent the more intense protein oxidation as assessed by formation of protein carbonyls and SB, highlighting the timely interaction between proteins and oxidizing lipids. Protein oxidation occurred concomitantly with loss of WHC and discolouration of beef patties. Mechanisms and consequences of the chemical modifications induced by oxidative stress in meat proteins are thoroughly discussed.     

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.     

Antioxidant effect of fractions from chicken breast and beef loin homogenates in phospholipid liposome systems

The antioxidant effects of meat fractions from chicken breast and beef loin were compared. Five meat fractions – homogenate (H), precipitate (P), supernatant (S), high-molecular-weight (HMW) and low-molecular-weight (LMW) fractions – were prepared from chicken breast or beef loin. Each of the fractions were added to a phospholipid liposome model system containing catalysts (metmyoglobin, ferrous and ferric ion) or iron chelating agents to determine the effects of each fraction on the development of lipid oxidation during incubation at 37 °C for 120 min. All fractions from chicken breast showed stronger antioxidant effects against iron-catalyzed lipid oxidation than those from beef loin. Iron chelating capacity of water-soluble LMW and water-insoluble (P) fractions from both meats were responsible for their high antioxidant capacities. High concentration of myoglobin, which served as a source of various catalysts, was partially responsible for the high susceptibility of beef loin to lipid oxidation. Storage-stable ferric ion reducing capacity (FRC) was detected in all fractions from both meats, and was a rate-limiting factor for lipid oxidation in the presence of free ionic iron. Higher antioxidant capacity and lower myoglobin content in chicken breast were primarily responsible for its higher oxidative stability than beef loin. DTPA-unchelatable compounds, such as ferrylmyoglobin and/or hematin were the major catalysts for lipid oxidation in beef loin, but free ionic iron and storage-stable FRC also played important roles during prolonged storage.     

Pro-oxidant activities of carnosine,rutin and quercetin in a beef model system and their effects on the metmyoglobin-reducing activity

The effects of carnosine, rutin and quercetin on oxidative processes and metmyoglobin (MetMb)-reducing activity in a beef model system were investigated. Ground beef was mixed with antioxidant solution at two concentrations. Storage period and antioxidant treatment negatively affected colour, colour stability and thiobarbituric acid-reactive substances values. Carnosine, rutin and to lesser extent quercetin accelerated discolouration, accumulation of MetMb and lipid peroxidation in the meat. The results suggest that these antioxidants acted as a pro-oxidants under the specified experimental conditions. The pro-oxidant activities were in the following order: carnosine>rutin>quercetin. The MetMb-reducing activity was not correlated with storage time, colour parameters, MetMb (%) or lipid oxidation. The MetMb-reducing activity was significantly reduced by 1 mM carnosine. However, there was no association between MetMb-reducing activity and colour stability during post-mortem storage.     

Impact of surfactant type, pH and antioxidants on the oxidation of methyl linoleate in micellar solutions

The oxidation of methyl linoleate micelles has been studied, aiming at elucidating the effect of various variables, including surfactant type, pH and antioxidants. The progress of the methyl linoleate oxidation was evaluated by measurement of conjugated dienes hydroperoxides (CDHP) and malondialdehyde (MDA). It was shown that the oxidative stability of methyl linoleate micelles was influenced by surfactant type, with oxidative rate being greater in SDS micelles than in Tween 20 micelles. Besides, the methyl linoleate micelles at pH 6.8 had greater rates of lipid oxidation than their pH 3.0 counterparts. Moreover, the incorporation of VE and VC in the methyl linoleate micelles successfully slowed the formation of hydroperoxides and their subsequent decomposition product MDA. However, the antioxidant activities of VE and VC were related to their concentrations.     

Effect of frozen storage duration and cooking on physical and oxidative changes in M. Gastrocnemius pars interna and M. Iliofiburalis of Rhea americana

This study was conducted to evaluate the effect of frozen storage time (30, 60, 90 or 180 days) and cooking (100 °C, 30 min) on the physical characteristics and oxidative stability of M. Gastrocnemius pars interna (GN) and M. Iliofiburalis (IF) of rhea americana. Physical parameters measured included thawing and cooking loss, colour parameters (L*a*b*), while oxidation was assessed by determining the TBA-RS, carbonyl and aromatic amino acid content. Prolonged frozen storage of rhea meat decreased lightness (L*), yellowness (b*), and increased the discoloration parameter hue angle and redness a*. During storage, muscle IF was more prone to lipid and myoglobin oxidation than muscle GN. Cooking loss declined with the increase of storage time and was higher in GN than in IF muscle. With cooking, TBA-RS, carbonyl content, and aromatic amino acids (phenylalanine, tyrosine, and tryptophan) were highly affected, but the extent of oxidation ranged according to muscle and duration of frozen storage.     

Temperature of frozen storage affects the nature and consequences of protein oxidation in beef patties

The effect of three frozen storage temperatures (− 8, − 18 and − 80 °C) on protein oxidation in beef patties was studied through the analysis of novel oxidation markers. Additionally, the connection between lipid and protein oxidation and the impact of the latter on particular quality traits (water holding capacity, color and texture) of subsequently processed beef patties (cooking/cold-stored) were investigated. Protein oxidation was measured as the loss of tryptophan fluorescence and formation of diverse lysine oxidation products (α-aminoadipic semialdehyde, α-aminoadipic acid and Schiff bases). Lipid oxidation was assessed by levels of thiobarbituric acid reactive substances and hexanal. A significant effect of storage temperature on protein oxidation was detected. Frozen storage increased the susceptibility of meat proteins to undergo further oxidation during processing. Timely interactions were found between lipid and protein oxidation. Plausible mechanisms by which oxidative damage to proteins may have an impact in particular quality traits are thoroughly discussed.