DEVELOPMENT OF LIPID OXIDATION AND INACTIVATION OF ANTIOXIDANT ENZYMES IN COOKED PORK AND BEEF

Physicochemical Properties of Chicken Breast and Thigh as Affected by Sous-Vide Cooking Conditions

Sous-vide is a cooking method used to improve the tenderness and juiciness of chicken breast. However, the comparative changes in meat quality attributes of sous-vide cooked chicken breast and thigh muscles are not fully understood. The objective of this study was to investigate the effects of sous-vide cooking conditions, based on collagen denaturation temperature of intramuscular connective tissue, on the physicochemical properties of chicken breasts and thighs. Chicken breast and thigh were cooked at four sous-vide cooking conditions (55 °C for 3/6 h and 65 °C for 3/6 h) and conventional cooking at 75 °C (core temperature of 71 °C) as control. No significant differences in pH and lightness were found between the sous-vide cooking conditions. Moisture content, cooking loss, protein solubility, shear force, myofibrillar fragmentation index, and lipid oxidation were affected by sous-vide cooking conditions (p < 0.05). The decreased shear force and total collagen content of 65 °C sous-vide cooking treatment might be associated with collagen denaturation (p < 0.05). Sous-vide cooking at 55 °C could decrease cooking loss, with higher moisture than sous-vide cooking at 65 °C (p < 0.05). These tendencies on water-holding capacity and shear force at the two different temperatures were similarly observed for both chicken breast and thigh. Therefore, this study indicates that chicken breast and thigh are similarly affected by the sous-vide cooking conditions and suggests that a novel strategy to apply together two temperature ranges based on the thermal denaturation of intramuscular connective tissue would be required.

Sous-vide cooking as a practical strategy to improve quality attributes and shelf stability of reduced-salt chicken breast ham

The objective of this study was to evaluate the general quality attributes and shelf stability of reduced-salt and sous-vide cooked chicken breast hams during 4 weeks of refrigerated storage (4°C). Four treatment groups of chicken breast ham were prepared using a 2 (salt level, 1.5% NaCl (regular) and 0.75% (reduced)) × 2 (cooking method, conventional and sous-vide) factorial arrangement. Based on each chicken breast weight, 20% NaCl solution was injected. Conventional cooking was done at 80°C until the core temperature reached 71°C, whereas sous-vide cooking was conducted at 60°C for 2 h. Sous-vide cooking could decrease cooking loss and shear force of reduced-salt chicken breast ham (P < 0.05). As a result, sensory scores for juiciness and tenderness of reduced-salt and sous-vide cooked chicken breast ham were similar to those of regular-salt and conventionally cooked chicken breast hams (P > 0.05). No adverse impacts on lipid oxidation and microbial safety were found in reduced-salt and sous-vide cooked chicken breast ham during 4 wk of refrigerated storage. Therefore, this study suggests that sous-vide cooking could be a practical thermal process for improving the water-holding capacity and texture of chicken breast ham without adverse impacts on shelf stability. Further studies on the combined application of sous-vide cooking with salt replacers would be warranted to improve the sensorial acceptance of saltiness of sous-vide cooked low-salt meat products.

Lipid oxidation induced by heating in chicken meat and the relationship with oxidants and antioxidant enzymes activities

The aim of the current research was to examine lipid oxidation in chicken meat heated to different temperatures followed by refrigerator storage and the factors contributing to lipid oxidation. It showed that lipid oxidation was significantly promoted when meat was heated up to 70°C and stored for 2 and 4 D as measured by thiobarbituric acid reactive substance. The monounsaturated fatty acids and polyunsaturated fatty acids also decreased significantly (P < 0.05) with the increase of heating temperature. The liberation of nonheme iron and increase of hydroxyl radical were observed in heated chicken meat, and the activities of antioxidant enzymes was decreased considerably at higher temperatures. The changes of these prooxidants and antioxidants might constitute a possible mechanism for the stronger lipid oxidation in heated meat.

Comparison of antioxidant compounds in pig meat from Italian autochthonous pig Suino Nero Lucano and a modern crossbred pig before and after cooking

This study aimed to evaluate and compare the antioxidant compounds of raw and cooked Longissimus lumborum muscles from Suino Nero Lucano (SNL) and a modern crossbred (CG) pig. Vitamin E, phenols, histidine-containing peptides, and superoxide dismutase (SOD) activity have been detected in the raw and cooked meat of both genetic types. Cooking process decreased the content of all considered antioxidant compounds (P < 0.05). The antioxidant compounds of meat were significantly influenced by genetic type (P < 0.001). Autochthonous SNL raw and cooked meat showed a higher endogenous antioxidants content (P < 0.001) and SOD activity (P < 0.02) compared to CG meat. The results of this research highlighted that the pig meat, in particular autochthonous pig meat, showed good concentrations of endogenous antioxidant compounds that could confer functional properties to the product.

Protective role of biogenic selenium nanoparticles in immunological and oxidative stress generated by enrofloxacin in broiler chicken

Presently most bacteria are becoming antibiotic resistant. Due to this there is a deficiency of potent antibiotics, therefore we have to preserve and improve the efficiency of existing antibiotics by mitigating the side effects. Enrofloxacin (EFX) is an important antimicrobial used in veterinary practice but it is known to exert immune suppression antioxidant stress. In the present study, we report on: (a) the biosynthesis of selenium nanoparticles (Se NPs), and (b) their protective effect in reducing adverse effects of EFX on broiler chicken. A potent bacterial strain, isolated from farm soil, has been identified as Pantoea agglomerans (GenBank: KU500622). It tolerates a high concentration of selenium dioxide (9 mM) and produces Se NPs under aerobic conditions. The obtained Se NPs are amorphous in structure and spherical in shape with sizes of less than 100 nm. The activity of cellular, humoral immune response and enzymatic and non-enzymatic antioxidants, has significantly been decreased as a result of EFX treatment. We investigated that Se NP supplementation greatly restores these values towards the control, and to even higher than those of the control. Adverse effects of EFX are prevented by simultaneous exposure to Se NPs (0.6 mg per kg of feed) in the diet of poultry chicken.

Antioxidant Enzyme Activity, Iron Content and Lipid Oxidation of Raw and Cooked Meat of Korean Native Chickens and Other Poultry

This study was conducted to observe antioxidant enzyme activity, iron content and lipid oxidation of Korean native chickens and other poultry. The breast and thigh meat of three Korean native chicken breeds including Woorimatdak, Hyunin black and Yeonsan ogye, and three commercial poultry breeds including the broiler, White Leghorn and Pekin duck (Anasplatyrhyncos domesticus) were studied. The analyses of the antioxidant enzymes activity, iron content and lipid oxidation were performed in raw and cooked samples. The activity of catalase (CAT) in the thigh meat was higher than that of the breast meat of three Korean native chickens and the broiler, respectively. The activity of glutathione peroxidase (GPx) in the uncooked thigh meat of three Korean native chickens was higher than that of the breasts. The breast meat of Woorimatdak and Pekin duck had higher superoxide dismutase (SOD) activity than the others, while only the thigh meat of Pekin duck had the highest activity. Cooking inactivated CAT and decreased the activity of GPx and SOD. The thigh meat of Woorimatdak, White Leghorn, Yeonsan ogye and Hyunin black contained more total iron than the breast meat of those breeds. The heme-iron lost during cooking ranged from 3.2% to 14.8%. It is noted that the thigh meat had higher thiobarbituric acid reactive substances values than the breast in all chicken breeds. Though Woorimatdak showed higher antioxidant enzyme activity and lower released-iron percentage among Korean native chickens, no differences were found on lipid oxidation. We confirm that the dark meat of poultry exhibited higher antioxidant enzyme activity and contained more iron than the white meat.

Evaluation of Various Packaging Systems on the Activity of Antioxidant Enzyme, and Oxidation and Color Stabilities in Sliced Hanwoo (Korean Cattle) Beef Loin during Chill Storage

The effects of various packaging systems, vacuum packaging (VACP), medium oxygen-modified atmosphere packaging (50% O₂/20% CO₂/30% N₂, MOMAP), MOMAP combined with vacuum skin packaging (VSP-MOMAP), high oxygen-MAP (80% O₂/20% CO₂/0% N₂, HOMAP), and HOMAP combined with VSP (VSP-HOMAP), on the activity of antioxidant enzyme, and oxidation and color stabilities in sliced Hanwoo (Korean cattle) beef loin were investigated at 4°C for 14 d. Higher (p<0.05) superoxide dismutase activity and total reducing ability were maintained in VSP-MOMAP beef than in HOMAP beef. Lipid oxidation (2-thiobarbituric acid reactive substances, TBARS) was significantly (p<0.05) retarded in MOMAP, VSP-MOMAP, and VSP-HOMAP beef compared with HOMAP beef. Production of nonheme iron content was lower (p<0.05) in VSP-MOMAP beef than in HOMAP beef. Red color (a*) was kept higher (p<0.05) in VSP-MOMAP beef compared with MOMAP, HOMAP, and VSP-HOMAP beef. However, VACP beef was found to have the most positive effects on the antioxidant activity, oxidation and red color stabilities among the various packaged beef. These findings suggested that VSP-MOMAP was second to VACP in improving oxidation and color stabilities in sliced beef loin during chill storage.

Effect of olive leaf (Olea europea L.) extracts on protein and lipid oxidation in cooked pork meat patties enriched with n-3 fatty acids

BACKGROUND

The effect of olive leaf extracts on lipid and protein oxidation of cooked pork patties refrigerated stored for 9 days was evaluated. Patties were prepared from longissimus dorsi muscle of pigs, and dietary supplemented with linseed oil.

RESULTS

Results showed that dietary linseed oil modified the fatty acid composition of pork patties by increasing (P ≤ 0.05) n-3 (α-linolenic acid) and decreasing (P ≤ 0.05) n-6 (linoleic acid) fatty acids. Olive leaf extracts at supplementation levels of 200 and, especially, of 300 mg gallic acid equivalents kg⁻¹ meat, delayed lipid oxidation by reducing (P ≤ 0.05) both primary (conjugated dienes and hydroperoxides) and secondary (malondialdehyde) oxidation products. They also inhibited protein oxidation in a concentration-dependent manner by reducing (P ≤ 0.05) protein carbonyls and increasing (P ≤ 0.05) protein sulfhydryls. In addition, they improved sensory attributes of the n-3 enriched patties.

CONCLUSION

Results suggested that olive leaf extracts might be useful to the meat industry as an efficient alternative to synthetic antioxidants.

Vitamin (B1, B2, B3 and B6) content and oxidative stability of Gastrocnemius muscle from dry-cured hams elaborated with different nitrifying salt contents and by two ageing times

The effect of the amount of added nitrate and nitrate plus nitrite to dry-cured hams on the vitamin (B1, B2, B3, B6) content, the antioxidant enzyme superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx) activities and the thiobarbituric acid reactive substances (TBARS) was assessed in Gastrocnemius muscle at the end of two ripening processes. Five different curing mixtures (Hi-N: 600 KNO3; Lo-N: 150 KNO3; Hi-Mix: 600 KNO3+600 NaNO2; Lo-Mix: 150 KNO3+150 NaNO2; Hi-Mix/Asc: 600 KNO3+600 NaNO2+500 sodium ascorbate, expressed as mg of salts added on surface per kg of fresh ham) were evaluated in dry-cured hams aged for 11.5months (standard process, SP) and 22months (long process, LP). Minor differences in target parameters between the hams due to the process were found. The amount of nitrate when it was added alone or as a mixture of nitrate and nitrite, as well as the ascorbate addition to dry-cured hams did not affect vitamin B1, B2 and B3 contents. The level of vitamin B6 was affected by both the amount and the mixture of salts; the addition of nitrite reduced around 40% the content of vitamin B6, but it was not affected by nitrate or ascorbate. The activity of SOD and CAT decreased with the amount of nitrate and nitrite, while GSHPx and TBARS resulted unaffected.

Antioxidant enzyme activities are affected by salt content and temperature and influence muscle lipid oxidation during dry-salted bacon processing

Fresh pork bacon belly was used as material and manufactured into dry-salted bacon through salting and drying-ripening. During processing both oxidative stability and antioxidant enzyme stability were evaluated by assessing peroxide value (PV), thiobarbituric acid reactive substances (TBARS) and activities of catalase, glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), and their correlations were also analysed. The results showed that all antioxidant enzyme activities decreased (p<0.05) until the end of process; GSH-Px was the most unstable one followed by catalase. Antioxidant enzyme activities were negatively correlated with TBARS (p<0.05), but the correlations were decreased with increasing process temperature. Salt showed inhibitory effect on all antioxidant enzyme activities and was concentration dependent. These results indicated that when process temperature and salt content were low at the same time during dry-salted bacon processing, antioxidant enzymes could effectively control lipid oxidation.

Kinetics of protein physicochemical changes induced by heating in meat using mimetic models: (2) effects of fibre type, peroxides and antioxidants

Heating-induced changes in meat proteins were investigated using models made of aqueous suspensions of myofibrils according to muscle fibre types and cellular compounds (oxidants and antioxidants). These changes were evaluated by measurements of carbonyl groups and protein surface hydrophobicity. Model results were compared to trial results obtained on pork meat (M. Longissimus dorsi) heated under the same conditions (45 and 75°C, from 5 to 120 min). Myofibrillar proteins from α-white fibres were more sensitive to oxidation and thermal denaturation than those from β-red fibres. At 45°C, there were negligible differences due to peroxide or antioxidant types. At 75°C, organic peroxides (ROOH) were less oxidative than hydrogen peroxide (H2O2), and antioxidant enzymes were less efficient than vitamin E and carnosine at protecting proteins against oxidation. Protein oxidation observed in meat is lower than in the mimetic models and the increase in hydrophobicity remained limited in meat.

Chemical composition, fatty acid content and antioxidant potential of meat from goats supplemented with Moringa (Moringa oleifera) leaves, sunflower cake and grass hay

The present study determined the chemical composition, fatty acid (FA) content and antioxidant capacity of meat from goats supplemented with Moringa oleifera leaves (MOL) or sunflower cake (SC) or grass hay (GH). The meat from goat supplemented with MOL had higher concentrations of total phenolic content (10.62±0.27 mg tannic acid equivalent E/g). The MOL significantly scavenged 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic-acid (ABTS) radical to 93.51±0.19% (93.51±0.19%) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical to 58.95±0.3% than other supplements. The antioxidative effect of MOL supplemented meat on catalase (CAT), reduced glutathione (GSH), superoxide dismutase (SOD) and lipid oxidation (LO) was significantly (P<0.05) higher than other meat from goat feed on grass hay or those supplemented with sunflower seed cake. The present study indicated that the anti-oxidative potential of MOL may play a role in improving meat quality (chemical composition, colour and lipid stability).

Influence of meat quality and NaCl percentage on glutathione peroxidase activity and values for acid-reactive substances of raw and dry-cured Longissimus dorsi

Fresh and dry-cured porcine loins (Longissimus dorsi) were analysed for glutathione peroxidase (GSHPx) activity and acid reactive substances (TBARS) in order to assess the influence of meat quality and salt (NaCl) concentration on oxidative stability. The results showed lower GSHPx activity and higher TBA levels in normal meat than in PSE meat indicating a higher oxidative stress in normal meat quality. GSHPx remained active at the end of the curing process. Higher salt concentration led to lower enzyme activity and TBARS values prompted the thought of a double role of NaCl as an enzyme inhibitor and as an antioxidant molecule.

Antioxidant activity of mechanically separated pork extracts

Utilization of synthetic carnosine as a food additive is limited by both regulatory and economic hurdles. Therefore, the potential of producing carnosine-containing antioxidant extracts from an underutilized skeletal muscle source, mechanically separated pork (MSP), was investigated. Carnosine-containing MSP extracts were capable of inhibiting lipid oxidation both in vitro and in salted ground pork. Heating (60-80°C) the MSP extract removed iron and increased in vitro antioxidant activity. Isolation of a low molecular weight fraction of the MSP extract by ultrafiltration was effective at decreasing iron but did not substantially increase in vitro antioxidant activity. Freeze dried extracts (untreated, 80°C, ultrafiltration permeate) were capable of inhibiting both TBARS and lipid peroxide formation in ground, salted pork stored at -15°C. While MSP extracts were capable of inhibiting lipid oxidation both in vitro and in salted, ground pork, their antioxidant activity was low suggesting that their use as a food additive would be impractical.

Antioxidant and other quality properties of reindeer muscle from two different Norwegian regions

The effects of origin, gender, age, and muscle type on chemical composition, colour, antioxidant status and sensory profile of reindeer muscles Longissimus dorsi (LD) and Semimembranosus (SM) from two production regions were investigated. For some variables, the comparison between reindeer and beef muscles was also included. Muscles from North Norway (NN) were darker and contained more myoglobin and moisture, and less protein and fat than muscles from Mid Norway (MN). Oxygen radical absorbance capacity (ORAC) was significantly higher in these muscles while the levels of antioxidant enzymes were significantly lower in contrast to MN muscles. Relative to male reindeer, muscles from females contained significantly more total phenols and showed higher antiradical power (ARP). Carcass weight and the sensory attributes colour, sharp and bitter flavour had higher scores for older animals. Considerable differences between LD and SM were revealed in sensory assessment. In comparison to beef reindeer meat was darker, had more myoglobin, total phenols, antioxidant enzymes, and higher ARP and ORAC values.

Effect of NaCl, myoglobin, Fe(II), and Fe(III) on lipid oxidation of raw and cooked chicken breast and beef loin

Chicken breast and beef loin were ground, and no, NaCl, NaCl+myoglobin, NaCl+Fe(II), or NaCl+Fe(III) additions were made; patties were then prepared. Half of the patties were packaged in oxygen-permeable bags and stored at 4 degrees C for 10 days, and the other half were cooked in a 95 degrees C water bath to an internal temperature of 75 degrees C, packaged in oxygen-permeable zipper bags, and stored at 4 degrees C for 7 days. The oxidative stability of raw and cooked chicken breast and beef loin were determined during storage. Chicken breast was more resistant to various exogenous oxidative factors than beef loin: addition of NaCl did not increase TBARS values and nonheme content of raw chicken breast, but significantly increased those of raw beef loin patties during storage. Addition of NaCl+Mb did not affect lipid oxidation in raw chicken breast patties, but decreased the TBARS of beef loin during storage. Addition of NaCl+Fe(III) or NaCl+Fe(II) increased the TBARS values of both raw chicken breast and beef loin during storage, but the increase was greater in beef loin than in chicken breast. The TBARS values of all cooked chicken breast and beef loin increased during 7 days of storage, but the increases in cooked chicken patties were significantly smaller than those of cooked beef loin patties with the same treatments. Addition of NaCl and cooking caused severe degradation of myoglobin, leading to a significant increase in free ionic iron content in beef loin. It is suggested that free ionic iron is the major catalyst for lipid oxidation, and the low "storage-stable and heat-stable" ferric ion reducing capacity in chicken breast were responsible for the high oxidative stability for raw and cooked chicken breast compared with beef loin under prooxidants, cooking, and storage conditions.

Endogenous factors affecting oxidative stability of beef loin, pork loin, and chicken breast and thigh meats

The susceptibility of meats from different animal species (chicken breast [CB] and thigh [CT], pork [PL and beef [BL]) to lipid oxidation was studied. The amounts of TBARS in raw PL, CB, and CT did not change during a 7-d storage period. TBARS values of raw BL, however, significantly increased during 7-d storage because of high heme iron content, high lipoxygenase-like activities, and low 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities. Ferric ion reducing capacities (FRC) were detected in all raw meats, but their characteristics were different: storage-unstable in CB and CT and storage-stable in PL and BL. Ferric ion reducing capacities in raw CB and CT was higher than those of PL and BL, and could be related to their high oxidative stability. The TBARS values of cooked meat increased significantly with storage. The rates of TBARS increase in cooked CT and BL were significantly higher than those of cooked CB and PL after a 7-d storage. Nonheme iron content in cooked BL was higher than other meats and increased significantly after 7 d. Cooked BL had a higher amount of heat-stable FRC, which acted as a prooxidant in the presence of high free ionic irons, than other meats. Therefore, high heat-stable FRC and increased nonheme iron content in cooked BL were responsible for its high susceptibility to lipid oxidation. Despite relatively low nonheme iron and heat-stable FRC levels, cooked CT showed similar levels of TBARS to cooked BL after a 7-d storage because of its high PUFA content.

Free radical scavenging activity of Lactobacillus fermentum in vitro and its antioxidative effect on growing-finishing pigs

AIMS

To evaluate the free radical-scavenging capacity of Lactobacillus fermentum and its effects on antioxidant enzyme levels in finishing pigs.

METHODS AND RESULTS

The free radical-scavenging activity of Lact. fermentum was analysed in vitro. The tested Lactobacillus showed a high scavenging ability against DPPH (1,1-diphenyl-2-picrylhydrazyl), superoxide and hydroxyl radicals which was dose dependent. Subsequently, 108 crossbred pigs weighing 20.67 BW, were allotted to dietary treatments including a basal diet or the basal diet supplemented with either aureomycin or 10.2 x 10(7) Lact. fermentum CFU g(-1) diet. Supplementation of Lact. fermentum increased total antioxidant capacity (P < 0.01) in serum from 50 kg pigs, while serum superoxide dismutase (P = 0.01) and glutathione peroxidase (P < 0.01) increased, and malondialdehyde levels decreased (P < 0.01) in 90 kg pigs. Hepatic catalase (P = 0.04), muscle superoxide dismutase (P < 0.01) and copper-zinc-superoxide dismutase were enhanced (P = 0.01), whereas malondialdehyde levels were reduced (P = 0.05) by Lact. fermentum.

CONCLUSIONS

The free radical-scavenging capacity of Lact. fermentum was dose dependent and its supplementation improved the antioxidant status of pigs.

SIGNIFICANCE AND IMPACT OF THE STUDY

Lactobacillus fermentum could be used to alleviate oxidative stress and increase pig performance and improve pork quality.

Effect of heating oxymyoglobin and metmyoglobin on the oxidation of muscle microsomes

Myoglobin (Mb) and its iron have been proposed to be major prooxidants in cooked meats. To understand the mechanisms and differentiate between the prooxidant and antioxidant potential of oxymyoglobin (OxyMb) and metmyoglobin (MetMb), their prooxidant activity, iron content, solubility, free radical scavenging activity, and iron binding capacity were determined as a function of thermal processing. The ability of native and heat denatured OxyMb and MetMb to promote the oxidation of muscle microsomes was different. MetMb promoted lipid oxidation in both its native and denatured states. Conversely, OxyMb became antioxidative when the protein was heated to temperatures >or=75 degrees C. The increased antioxidant activity of heat denatured OxyMb was likely due to a decrease in its prooxidative activity due to its loss of solubility. These data show that the impact on oxidative reactions of Mb is the result of the balance between its antioxidant and prooxidant activities.

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 alpha-tocopheryl acetate and beta-carotene dietary supplementation on the antioxidant enzymes, TBARS and sensory attributes of turkey meat

1. The aim of the study was to evaluate the effects of alpha-tocopheryl acetate (50 mg/kg) and beta-carotene (15 mg/kg) dietary supplementation on the oxidative status of raw turkey breast and leg muscles assessed by thiobarbituric acid test values, the vitamin E levels and the antioxidant enzyme activities. In parallel, a quantitative descriptive sensory analysis was carried out on cooked, stored and reheated samples. 2. Vitamin E was present in sufficient quantity to reduce oxidation, since iron-induced reactive substances (TBARS) were significantly lower in antioxidant-supplemented treatments. The results suggested that the presence of beta-carotene in the diet limits the accumulation of alpha-tocopherol in turkey muscles. 3. In the present study, there was no conclusive relationship between dietary antioxidant supplementation and endogenous antioxidant enzyme activities. 4. Sensory evaluation showed that a longer supplementation time and dose may be necessary in turkeys to prevent meat from rancidity and warmed-over flavour (WOF). Leg pastiness and stringiness were modified by dietary antioxidant supplementation, indicating the possible synergism between antioxidants and cysteine proteinases in the perception of meat quality. 5. Given the modern trends that lead consumers to increase their consumption of poultry meat, it would be interesting to evaluate the commercial potential and cost effectiveness of routine dietary antioxidant supplementation.

Influence of enrofloxacin administration and alpha-tocopheryl acetate supplemented diets on oxidative stability of broiler tissues

The objective of this study was to assess the oxidative stability and presence of antibiotic residues in tissues of broilers fed diets supplemented with alpha-tocopheryl acetate and treated with enrofloxacin. The activities of antioxidant enzymes and antibiotic concentrations in chicken breast, leg, and liver were determined. Iron-induced TBA-reactive substances (TBARS) and vitamin E were evaluated in muscles. The antioxidant effectiveness of vitamin E was reflected by TBARS values being lower in antioxidant-supplemented treatments than in the other dietary groups. On the other hand, antioxidant enzyme activities were not substantially affected by dietary treatments. The concentration of enrofloxacin in tissues was considerable, even after withdrawal 12 d before slaughter. Contrary to the findings in previous studies, enrofloxacin was not extensively metabolized to ciprofloxacin. Supplementation of the diet with 100 mg/kg of alpha-tocopheryl acetate did not have a significant effect on the level of antibiotic found in breast muscle samples. When comparing treatments without antibiotic withdrawal time, alpha-tocopheryl acetate supplementation led to a significant decrease in enrofloxacin level in leg and liver samples. These results showed that mutual interactions between different molecules could modify the drug residues in the tissue, which should be taken into account when considering the drug administration and the establishment of a correct withdrawal time.