Effects of Postmortem time of calcium chloride injection on beef tenderness and drip, cooking, and total loss

The effect of postmortem time of calcium chloride (CaCl(2)) injection in conjunction with postmortem aging was determined on 16 beef semimembranosus muscles. Each muscle was cut into four equal segments that were randomly assigned: (1) no injection (control); (2) CaCl(2) at 1 h postmortem; (3) CaCl(2) at 12 h postmortem; or (4) CaCl(2) at 24 h postmortem. Samples were injected with a 0·3 m solution of CaCl(2) at 10% by weight. At 24 h postmortem, each segment was divided into two pieces that were randomly assigned to either a 10-day aging period (2°C) or to frozen storage (-29°C). Shear force values were higher (P < 0·01) in control samples compared with injected samples and increased linearly (P < 0·05) with time of injection. Drip loss was lower (P < 0·01) in control samples compared with injected samples. A linear (P < 0·05) effect was found for the increases in cooking and total loss due to injection time. Aging decreased (P < 0·05) shear force values and cooking loss. CaCl(2) injection at 1 h postmortem was most effective in reducing shear force values and preventing excessive moisture loss. However, injection at 12 or 24 h postmortem was also effective in lowering shear force values.     

宰后成熟过程中猪肉保水性的变化

以三元猪背最长肌为研究对象,在第4、8、12、16、20、24、28、32和36 h分别检测蒸煮损失率、滴水损失率、贮藏损失率、剪切力值和pH值的变化情况,研究宰后成熟过程中猪肉保水性的变化规律。结果表明,蒸煮损失率呈先升高后降低的趋势,在第20 h蒸煮损失率达到最大值32.80%;贮藏损失率和滴水损失率呈先下降后上升再下降的趋势;剪切力值在4~12 h内显著性上升（p<0.05）,且在12 h达到最大62.29 N;pH值呈整体先下降后上升再下降最后趋于稳定的变化趋势;其中,成熟时间与剪切力值呈显著负相关（p<0.01）,pH值与蒸煮损失率呈极显著负相关（p<0.01）,滴水损失率与贮藏损失率呈较高的相关性（p<0.01）。综合指标,猪肉在宰后成熟36 h内保水性有先变弱后增强的趋势,在12~16 h内进入僵直高峰点,随后进入解僵成熟期。该研究结果可为后续深入研究宰后成熟过程中猪肉嫩度变化规律及机理提供基础指标和参考依据。     

禁食时间对宰后早期鸡肉持水力和嫩度的影响

三黄鸡分别禁食0、8、16h和24h,三管齐断法宰杀,于宰后5h内分别测定滴水损失、蒸煮损失、加压损失、蛋白溶解性、剪切力值、糖原、乳酸和pH值等指标,观察禁食对宰后早期鸡肉持水力和嫩度的影响。结果表明：随着禁食时间延长,宰后糖原含量(P＜0.05)和pH值均降低;随着宰后时间延长,糖原含量和pH值变化趋势与宰后时间正相关,而乳酸含量变化趋势与宰后时间负相关。宰后早期,pH值对肌肉持水力有显著影响(P＜0.05),而蛋白溶解度对持水力变化贡献不大。禁食使得宰后早期肌肉剪切力值有增大趋势,但处理组之间差异不显著。与未禁食鸡相比,禁食8h和禁食16h能够提高宰后肌肉持水力。     

Hot cutting of goat carcasses following early post-mortem high temperature ageing

Hot cutting of goat sides into bone-in joints, such as leg, shoulder and loin, 3 h after the sides were left hanging at an ambient temperature of 34°C with (treatment II) or without (treatment I) subsequent chilling prior to freezing did not adversely affect colour of meat, tenderness, cooking loss or water-holding capacity compared with normal chilling. The latter process (treatment III) significantly (P < 0·05) increased evaporative weight loss from the sides. Differences in colour, shear force, evaporative weight loss, cooking loss, drip loss from the leg joint and water-holding capacity between treatment I, where sides were hung at room temperature for 3h, and treatment II, where sides were given an additional chilling period of 21h after hanging, were not significant. These findings indicate that, in countries with ambient temperatures above 30°C, goat sides or carcasses can be cut hot after a 3h hanging period at ambient temperature and subsequently frozen without deterioration in the quality or processing properties of the meat.     

Liberation of actin from actomyosin in meats heated to 65°C

This study investigated whether actin liberation from myofibrils occurs during the heating of various muscles, as well as squid mantle muscle at temperatures, such as 60°C, employed for vacuum cooking of meats. Actin liberation was demonstrated in scallop striated adductor muscle, but not in beef, pork, or chicken, using the detection method previously employed with squid muscle, in which liberated actin was detected with SDS-PAGE, in the supernatant obtained by centrifugation of the homogenate of heated muscle in 0.2M KCl at a neutral pH. However, actin liberation was demonstrated in beef, pork and chicken by a new detection method, in which heated muscle was homogenized in 0.6M KCl or NaCl at a slightly alkaline pH and maintained at 4°C for 16h with stirring, after which the homogenate was diluted three times with water and centrifuged to obtain the supernatant containing the liberated actin. This new method indicated that actin liberation in beef, pork, and chicken was marked by heating at 65°C, but scarcely induced at 80°C. Thus, the liberation of actin from myofibrils may contribute to the greater tenderness of vacuum-cooked meat (meat heated at a low temperature for long time), as compared with meat prepared by cooking at a higher temperature.     

Influence of temperature on the rate of post-mortem metabolism and water-holding capacity of bovine neck muscles

Strips of forty bovine neck muscles were placed at temperatures in the range -1° to +30°C within 45 min of slaughter and stored for up to 24 h. Strips were taken at various times during storage and assayed for pH, 'R' value (degree of transformation of ATP to IMP) and ATP concentration. The water-holding capacity (WHC) of the intact muscle was compared with the WHC of a salted muscle homogenate prepared at each sampling time. The rate of pH fall post mortem was relatively low around +5°C and increased at lower or higher temperatures. ATP concentration showed a delay phase dependent on storage temperature and a subsequent rate of depletion which was also temperature dependent. The patterns of change in WHC of the muscle samples and the salted homogenates differed, the former showing a rapid fall to a fairly steady level shortly after initiation of storage, the latter showing no appreciable change until the onset of rigor. It is suggested that salting meat at any time prior to the onset of rigor will confer improved WHC and that the temperature of storage post mortem should be chosen to induce low rates of ATP turnover so as to prolong the feasible delay between slaughter and salting.     

The effects of different chilling methods on meat quality and calpain activity of pork muscle longissimus dorsi

The objective of this study was to investigate the effects of conventional chilling (0 to 4 °C), rapid chilling (RC, -20 °C for 30 min, followed by 0 to 4 °C), and short-duration chilling (0 to 4 °C for 30 min, followed by 25 °C) on meat quality and calpain activity of pork muscle longissimus dorsi (LD). The muscle quality characteristics pH, color, cooking loss, pressing loss and tenderness, and calpain activities were measured 0-, 3-, 12-, and 24-h postmortem. Results show that the RC resulted in a faster temperature decline of the muscle, and prevented the meat pH and Commission Internationale de l'Eclairage L* value from declining during postmortem aging. RC also reduced meat cooking loss and pressing loss compared with the other two chilling methods. However, the chilling methods did not significantly affect meat shear force. During the first 24-h postmortem, there was not a noticeable change in the activity of m-calpain. But μ-calpain activity decreased regardless of chilling method. In the rapidly chilled carcasses, μ-calpain activity remained the same 3- and 12-h postmortem. However, in the short-duration chilled and conventionally chilled carcasses, the activity was visibly reduced. At 24-h postmortem, no clear zones on the gel were observed in all three treatments. PRACTICAL APPLICATION: Conventional and RC methods are commonly used for pork in commercial practice nowadays. Compared with conventional chilling, the effect of RC on quality parameters of pork varies. In recent years, short-duration chilling (SC) is widely used in many Chinese pig slaughtering facilities. However, few researchers have studied the effect of SD on pork quality. Therefore, the present study investigated the effect of different chilling methods on functionalities or quality of chilled pork meat.     

Residual glutamic-oxaloacetic transaminase (GOT) activity in thermally processed poultry and poultry products as an indicator of end-point temperatures

Glutamic-oxaloacetic transaminase (GOT) activities in chicken and turkey thigh and breast meat samples, thermally processed at 60–84°C in a model heat-treating system, were evaluated for use as indicators of end-point cooking temperatures (EPT). Wings, breasts, thighs and legs from commercially cooked, whole, roasted chickens and commercially processed products containing chicken and turkey meat were analyzed also to determine if residual GOT activities would indicate compliance with recent FDA/FSIS EPT recommendations. Activities of samples processed in the model system decreased logarithmically with increasing temperatures. GOT activities were higher (P < 0·05) in thigh meat than breast meat in both chicken and turkey samples; activities were higher in turkey than chicken. GOT values for chicken thigh and breast meat at 74°C, the FDA/FSIS recommended EPT for use by food handlers and retailers, were 735 and 164 Sigma-Frankel units ml^?1 (SFU ml^?1), respectively. Values for turkey thigh and breast meat at this temperature were 1080 and 450 SFU ml^?1, respectively. The range of activities was 7–13 SFU ml^?1 in commercially prepared chicken products and 27–161 SFU ml^?1 in turkey products. Analysis of these products showed adequate cooking and compliance with FDA/FSIS recommended EPT for retail sale. These data indicate that residual GOT activity in processed poultry has potential for use as an indicator of EPT.     

The effect of electrical stimulation, time of boning and high temperature conditioning on sensory quality traits of porcine Longissimus dorsi muscle

The effects of electrical stimulation (300 V, 1 A, 50 Hz, AC, 30 s) and high temperature conditioning (4h/15°C) on sensory quality traits of hot- and cold-boned, vacuum-packaged longissimus dorsi muscle of halothanenegative pigs were assessed at 12 days post mortem. Electrical stimulation accelerated the pH fall significantly, but had negligible effects on all quality traits measured, i.e. shear force, drip formation, fresh meat colour, cooking loss and degree of sarcoplasmic protein denaturation (p > 0·05). As compared with cold boning, hot boning significantly lowered drip losses (p < 0·05). Shear forces, which increased as a result of hot boning (p < 0·05), were reduced again through a 4 h/15°C conditioning period before chilling at 1 ±1°C. In addition, high temperature conditioning resulted in significantly lower drip losses (p < 0·05). It is suggested that prevention of cold-induced reduction of proteolytic enzyme activity is primarily responsible for both these findings.     

Effect of different air/steam convection cooking methods on turkey breast meat: physical characterization, water status and sensory properties

Turkey breast samples were cooked using a forced convection oven at three relative humidity levels (RH=8, 35 and 88%) at 100°C. Cooking parameters (temperature, cook value, and yield), textural and sensory properties as well as water status of the samples were evaluated. The application of different RH levels resulted in different cooking performances and cooked meat quality. Low steam cooking conditions (RH=35%) significantly increased cooking yield (7% higher than the high steam cooking), moisture content and water-holding capacity and had a positive effect on perceived tenderness, as shown by sensory analysis, where steam cooked samples were perceived as the most tender. The more mobile protons of (1)H T(2) (relaxing at times longer than 1s) in low steam samples were related to the higher perceived tenderness. Low steam cooking allowed for less water consumption, making this process an attractive cooking method as compared to high steam, as it also resulted in higher quality cooked turkey meat.     

Effects of temperature conditioning on postmortem changes in physico-chemical properties in Korean native cattle (Hanwoo)

The objective of this study was to examine the changes in physico-chemical properties that occur after adjusting postmortem chilling temperatures in Hanwoo beef. The right sides of beef carcasses were chilled for 4h at 2°C, 4h at 12°C and 16h at 2°C. The left sides were used as controls, chilled for 24h at 2°C. It took 8h for the control carcasses to cool down to <10°C and 10h 20min for the treatment. Adjusting the chilling temperature could be effective in lowering the postmortem pH and glycogen content. Treatment muscles at least 8h postmortem had longer sarcomeres than the control (P<0.05). The shear force in treatment carcasses at day 1 was similar to that of the control at day 6. Alternate chilling temperature had no detrimental effect on drip, cooking, total loss or color. Total numbers of aerobic plate counts were not significantly different between the control and treatment.     

Influence of freezing method on thaw drip and protein loss of low-voltage electrically stimulated and non-stimulated sheeps' muscle

South African Mutton Merino wethers (n = 32) were slaughtered, yielding carcasses with a mean weight of 22·18 ± 2·11 kg. Sixteen carcasses were electrically stimulated (ES) (21 V, 60 Hz, 120 s) immediately and all carcasses were chilled at room temperature (16°C) for 3 h and then overnight at 4°C, 95% RH. Both left and right Mm. longissimus lumborum et thoracis were excised and cut into six portions (77 g ± 7·8 g), each placed separately in a polyethylene bag and randomly allocated to five freezing treatments. These were: (1) cryogenic, -65°C; (2) cryogenic, -90°C; (3) walk-in-freezer, -21°C; (4) blast freezer, -21°C; (5) domestic freezer, -25°C. The respective freezing rates were 4·4, 6·4, 0·55, 0·35 and 0·51 cm h(-1) to -2·2°C at core depth of 1 cm below the surface. Samples were frozen to core temperatures of -20°C, removed and placed in a storage freezer (-20°C) for 48 h and 2·5 months. Samples were then suspended in perforated bags in a chiller (4°C) to thaw, and drip was collected in outer bags over the periods 0-24, 24-48, 48-72 and 72-96 h and expressed as g (100 g)(-1). Freezing methods had significant (P < 0·01) influences on drip loss in both ES and NES samples. Following storage for 48 h post-freezing at -20°C, total drip (g (100 g)(-1)) over 96 h of both ES and NES samples for the five freezing treatments were respectively: (1) 7·61 and 4·61; (2) 7·35 and 3·29; (3) 9·44 and 4·68; (4) 9·07 and 5·43; (5) 10·58 and 5·15. Following storage for 2·5 months, the total ES and NES drip were respectively, (1) 11·25 and 9·38; (2) 10·36 and 9·15; (3) 13·72 and 12·65; (4) 13·70 and 12·26; (5) 11·92 and 11·29. Total protein in the drip did not differ between freezing treatments. Differences between ES and NES samples did occur in the 48 h storage group. It is concluded that cryogenic freezing results in less thaw drip than the vapour compression systems. This advantage of cryogenic freezing disappears if meat is stored for long periods at -20°C. Electrical stimulation increases the drip loss in samples frozen for 48 h, but the differences are not significant after 2·5 months frozen storage. Protein losses parallel the drip.     

Lipid Oxidation Potential of Beef, Chicken, and Pork

Beef and pork longissimus dorsi and semimembranosus muscles and chicken breast and thigh muscles were excised 24 hr postmortem from carcasses of marketweight grain-finished feedlot beef cattle, marke-tweight hogs on a typical finishing diet, and broilers on a commercial grain diet. Muscle samples were immediately ground and formed into patties and stored raw or after cooking, at 4°C (cooked) or ?20°C (raw and cooked). TBA values (on sample weight basis) of frozen raw samples were higher for beef and pork than for chicken, as was heme iron content. However, TBA values of cooked samples were highest for chicken thigh muscles, which contained the most polyunsaturated fatty acids, at all storage temperatures.     

Cholesterol oxides in processed chicken muscle as influenced by dietary α-tocopherol supplementation

The effect of dietary α-tocopheryl acetate supplementation on the formation of cholesterol oxidation products (COPs) in chicken muscle during storage was investigated. Broiler chicks (Cobb 500 strain) were fed diets supplemented with 20, 200 or 800 mg α-tocopheryl acetate kg(-1) feed. Cooked breast and thigh muscle patties were prepared and stored at 4 °C for up to 12 days. Dietary supplementation significantly (p < 0.05) increased α-tocophenol concentrations in cooked muscle and decreased thiobarbituric acid-reacting substances (TBARS) during storage. COPs increased during storage. Total COPs ranged from 0.17-3.48 and 2.49-5.79 μg g(-1) in breast and thigh meat, respectively. TBARS and total COPs were linearly correlated in breast (r = 0.68, p < 0.001,) and thigh patties (r = 0.75, p < 0.05). Dietary α-tocopheryl acetate supplementation significantly (p < 0.05) reduced the formation of COPs during storage. Total COPs formed after 12 days were reduced by 42 and 75% in breast, and 50 and 72% in thigh, at supplementation levels of 200 and 800 mg kg(-1) feed, respectively.     

Carbon monoxide-heme pigment is responsible for the pink color in irradiated raw turkey breast meat

Turkey breast muscles were aerobically or vacuum packaged, irradiated at 0, 2.5, or 5.0 kGy using a Linear Accelerator (electron beam), and stored at 4°C. The CIE color values, reflectance scan, oxidation-reduction potential (ORP), production of gaseous compounds, and lipid oxidation of samples were determined at 0, 1, and 2 weeks of storage. Absorption spectra of sample drips were determined at 1 week of storage. Irradiation increased the a-value of both aerobically and vacuum-packaged turkey breast, but vacuum-packaged meat had stronger intensity than the aerobically packaged. The increased redness in vacuum-packaged meat was stable during the 2 weeks of storage. The production of CO in meat, which can bind to myoglobin as a sixth ligand, was proportional to irradiation dose. The ORP was decreased by irradiation, but was increased during storage. The ORP and lipid oxidation values were lower in vacuum-packaged than those in aerobically packaged turkey breast. Therefore, increased a-values in irradiated turkey breast should be caused by the decreased ORP and heme pigment-CO ligand formation. The absorption spectra of meat drip also showed that the peak wavelengths of irradiated turkey breast were similar to that of the CO-myoglobin.     

Lipid Oxidation in Cooked Turkey as Affected by Added Antioxidant Enzymes

Catalase (CAT) and glutathione peroxidase (GSH-Px) were added to turkey which had been cooked (80°C) to provide minimal activity of both enzymes, to determine their effects in development of lipid oxidation. CAT (100–500 U/g muscle) decreased the formation of thiobarbituric acid reactive substances (TBARS) 4–28% during 2 days of storage. GSH-Px (4.0 U/g muscle) decreased TBARS 8–11%. CAT (170 U/g muscle) and GSH-Px (1.3 U/g muscle) in combination decreased TBARS formation 7–14%. Reduced glutathione concentrations in the turkey were unaffected by cooking. These data suggest that heat inactivation of CAT and GSH-Px was not the only factor involved in heat-induced lipid oxidation reactions in turkey thigh muscle.     

Effect of Postmortem Storage on Titin and Nebulin in Pork and Poultry Light and Dark Muscles

Purified myofibrils were prepared from samples of chicken breast and thigh muscles and from light and dark portions of pork semitendinosus muscle at death and after storage at 4° and 22°C for 1, 3, and 7 days postmortem. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to examine the effect of postmortem storage of muscle on titin and nebulin. Results indicated that titin and nebulin were more rapidly degraded in light than in dark chicken muscle. In contrast, titin and nebulin were more rapidly degraded in dark than in light pork muscle.     

Effects of thawing temperature on the physicochemical properties of pre-rigor frozen chicken breast and leg muscles

The objective of this study was to evaluate effects of thawing temperature on the biochemical and physicochemical properties of pre-rigor frozen chicken breast and leg muscles. Breast and leg muscles from 24 broiler chickens were excised within 10min postmortem. Pre-rigor muscles were frozen at -20°C and thawed at 0 and 18°C, and pH, R-value, sarcomere length, muscle shortening, thaw and cook loss, shear force and myofibrillar fragmentation index (MFI) compared with those in pre-rigor or 2°C chilled muscles. The ultimate pH of 18°C thawed muscle was lower than that of 0°C thawed and 2°C chilled muscles. As expected, the shortening of sarcomere length and muscle length of thaw rigor muscles were more than those of chilled muscle, but there were no significant differences between chilled muscle and 0°C thawed muscle. Also, there were no significant differences in R-value (Abs 250/Abs 260) and cook loss due to thawing temperature. Samples thawed at 0°C had higher MFI and lower shear value than samples thawed at 18°C. Shear force value and MFI were not significantly different between chilled muscle and 0°C thawed muscle. By thawing at 0°C, thaw shortening was prevented, and tender meat comparable to the chilled meat was obtained.     

On the assessment of water-holding capacity of hot- vs cold-boned pork

The effects of time of boning and storage period on creatine kinase (CK) activity, transmission value, drip losses and water-holding capacity (WHC) measured by various methods was investigated. At 40 min post-mortem 30 pig carcasses with pH values > 6·2 in the loin were selected. The right loin of each carcass was hot boned and vacuum packaged immediately. The left loin was cold boned and packaged after overnight chilling at 2 ± 2°C. After 1, 5 and 12 days of storage at 0 ± 1°C, 10 hot- and cold-boned loins were unpacked and sampled. Time of boning did not affect drip losses. At 1 day post-mortem the CK activity was higher in hot- than in cold-boned pork. Sarcomere lengths were not affected by time of boning. The WHC was investigated by two controlled methods. A filter-paper press method was not sensitive enough to assess differences in WHC of hot- vs cold-boned pork. The results of a gravimetric method depended on the sample location. Results of the gravimetric test decreased with increasing storage periods. The results suggest that under the experimental conditions the chilling rates of hot-boned vs carcass-attached muscles were similar.     

Simultaneous lipolytic and oxidative changes in turkey meat stored at different temperatures

Samples from turkey breast and thigh muscle were taken from freshly slaughtered birds under sterile conditions and stored at 37, 4 or ?18°C for up to 24 months. Changes in lipid fractions, fatty acids compositions and oxidised products were determined at intervals. Lipolysis of phospholipids was observed at 37 and at 4°C and to a small extent at ?18°C, with little change in triglyceride levels. Free fatty acid levels in general increased as phospholipids decreased. Oxodienes and conjugable oxidation products increased with time of storage, the latter products being negatively correlated with phospholipid concentrations. Changes in the ratio of tetraene to triene conjugated oxidation products formed indicated that some preferential oxidation of fatty acids more unsaturated than linoleic acid was occurring initially and this was followed by an increase in the proportion of dienes being oxidised. Both lipolysis and oxidation were faster in thigh than in breast muscle (P < 0.01) in the stored meat and in in-vitro systems. It is concluded that lipolysis and oxidation interact in the degradation of lipids during storage of turkey meat.