电刺激结合冷却排酸对牦牛细胞骨架蛋白（Desmin、Troponin-C、Integrin）降解影响的研究进展

本文旨在介绍电刺激在牦牛肉类工业中的应用与研究及其机理。根据电刺激对骨架蛋白Desmin、Troponin-C、Integrin降解的影响机理,在此基础上讨论电刺激结合冷却排酸对骨架蛋白降解的机理。      

The effect of chilling, electrical stimulation and conditioning on pork eating quality

The effect of three different post-slaughter treatments and subsequent conditioning times on the eating quality of pork was studied, using a total of 72 pigs (80–90 kg live wt). The treatments were: (A) holding in air at > 10°C for 3 h, followed by chilling in air at 1°C; (B) chilling in air at 1°C; (C) high voltage electrical stimulation (ES) at 20 min post-slaughter, followed by Treatment B. The quality attributes were measured in M. longissimus thoracis et lumborum (LTL) and in M. semimembranosus (Sm).

There was little difference in cooling rate between the three treatments; the major effect on quality came from the use of ES in Treatment C. ES reduced pH at 45 min by approximately 0·3 units, and achieved pH values at 3 h post-slaughter of 5·64 (LTL) and 5·87 (Sm) but did not produce PSE meat. Drip losses were generally low, but were slightly higher with Treatment C. By all three instrumental texture parameters, LTL from Treatment C was significantly more tender than from A and B at 4, 7 and 12 days post-slaughter, suggesting that either some cold toughening with A and B was overcome by ES in treatment C or that ES had some other beneficial action. Conditioning at 1°C improved the tenderness of LTL from 4 to 7 days and further to 12 days. Taste panelling of loin chops and Sm roasts confirmed that Treatment C gave significantly more tender meat than A and B, and that ageing from 4 to 7 days and further to 12 days significantly improved tenderness. High voltage electrical stimulation at 20 min post-slaughter followed by cooling in air at 1°C (Treatment C) produced loin muscle which was more tender at 4 days than at 12 days with the other treatments.     

Effect of different electrical stimulation and chilling treatments on pork quality

The effect of different chilling and electrical stimulation (ES) treatments on the carcass and eating quality of pork has been examined. Preliminary trials (Study I), with a variety of ES treatments, indicated that, on the basis of pH fall, drip loss and tenderness, the most effective was that using 700 V peak at 12·5 Hz for 90 s applied at 20 min post-slaughter. These ES parameters were used throughout the main study (II) using 80 pigs, one side of which was stimulated and the other not, before being chilled rapidly (10°C in deep loin within 2–3 h of slaughter) or conventionally (10°C in deep loin within 5 h of slaughter).

Changes in pH and temperature during chilling were observed and, after chilling, quality assessments on LD and Sm muscles included drip loss, muscle opacity and instrumental toughness at 3 days post-slaughter.

Electrical stimulation, 20 min post-slaughter, improved tenderness of the LD and, to a lesser extent, the Sm of rapidly chilled pig sides. This advantage was gained without producing PSE pork. In fact, drip loss from the LD was consistently less from the sides which had been stimulated.     

低压电刺激和冷却方式对猪肉品质特性的影响

采用2×2析因设计研究了低压电刺激和冷却方式对猪肉品质特性,包括背最长肌温度、pH、肉汁损失、煮制损失和剪切力的影响。结果表明,低压电刺激加快猪背最长肌pH下降,增大剪切力,对持水性有不利影响;二阶段冷却加快猪背最长肌温度下降,减缓pH的下降速率,显著降低肉汁损失,对剪切力没有显著影响。回归分析表明,煮制损失最能反映猪肉剪切力。采用二阶段冷却或低压电刺激配合二阶段冷却工艺可以保持良好的猪肉品质。     

Effects of electrical stimulation, chilling temperature and hot-boning on the tenderness of bovine muscles

The objective of this study was to determine the effects of hot-boning, low voltage electrical stimulation (ES) and chilling temperature on the tenderness of bovine M. longissimus dorsi (LD) and M. semimembranosus (SM) muscles. LD (n=32) and SM (n=32) muscles were subjected to different post-mortem treatments; hot-boning (before 90min post-mortem), cold-boning (at 48h post-mortem), low voltage ES and rapid or slow chilling. Hot-boned muscles which were not electrically stimulated (NES) had higher Warner Bratzler shear force (WBSF) values (P<0.001) and shorter sarcomeres (P<0.001) than cold-boned muscles. Hot-boned muscles subjected to ES had lower pH values (P<0.001) post-stimulation and up to 8h post-mortem than NES muscles. At both chilling temperatures WBSF values were lower in ES hot-boned LD and SM muscles at days 2, 7 and 14 post-mortem than NES muscles. Hot-boned muscles subjected to slow chilling had longer sarcomeres (P<0.001) than those subjected to fast chilling. In hot-boned SM muscles, ES resulted in longer sarcomere lengths (P<0.001). However, ES did not have a significant effect on the sarcomere length of LD muscles. As indicated by WBSF values all muscles tenderised during ageing, including muscles which were 'cold shortened'. Proteolysis was not the main reason for differences in WBSF values between ES and NES muscles as judged by qualitative sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). A combination of slow chilling and ES had a positive effect on hot-boned muscles with respect to WBSF values.     

Bovine Longissimus dorsi muscle glycogen and color response as affected by dietary regimen and post-mortem electrical stimulation in young bulls

Eighty bulls were assigned to one of two groups and fed a dietary regimen to defer or accelerate growth until slaughter. Bulls fed at an accelerated rate of growth (or high energy regimen) had higher post-mortem pH, and lower muscle glycogen stores, with darker lean color, and improved shear and palatability traits compared to deferred fed animals. Bulls fed at an accelerated rate of growth also had a higher degree of marbling and USDA quality grade. Electrical stimulation did not affect (P > 0·05) ultimate pH, but reduced (P < 0·05) glycogen values at 0 and 2 h post mortem. Electrical stimulation also improved muscle color, lowered cooking losses and improved the palatability of cooked longissimus dorsi steaks.     

High voltage electrical stimulation enhances muscle tenderness, increases aging response, and improves muscle color from cabrito carcasses

Our study examined high and low voltage electrical stimulation and postmortem storage as strategies to improve tenderness and lean color in cabrito carcasses. Boer cross (n=60) kids were assigned to either high (550 V), low (20 V), or no electrical stimulation treatments. No differences in muscle temperature were observed between treatments at any time measured. Muscle pH declined fastest in high voltage treated carcasses. High voltage electrical stimulation slightly increased (P<0.05) b^* and a^* in the M. gluteus medius and tended to increase L^* and b^* (P=0.06 and 0.11, respectively) values in the M. longissimus thoracis. Electrical stimulation had no effect on myofibril fragmentation at 1-, 3-, or 14-d postmortem or sarcomere length. High voltage electrical stimulation increased (P<0.05) tenderness at 1- and 3-d postmortem, but not at 14-d postmortem. Aging for 3 d did not affect tenderness regardless of stimulation treatment, but aging time for 14 d improved (P<0.05) tenderness. These data indicate that high voltage electrical stimulation and 14 d aging were effective in improving the tenderness of meat from cabrito carcasses.     

Effect of electrical stimulation, high temperature conditions and ageing on muscle myofibrillar proteins

Electrical stimulation, when accompanied by high temperature incubation, was found to lower the extractability of myofibrillar proteins and increase their degradation, particularly that of the myosin component. Troponin T and myosin light chain 2 were similarly affected. Troponin T and troponins I and C were degraded earlier during ageing in electrically stimulated muscles incubated at high temperature than in conventionally chilled muscles.     

Ripening tomato fruit after chilling storage alters protein turnover

BACKGROUND: Tomato fruit is of prime importance owing to its qualities for human nutrition and its economic value. In order to extend its commercial life, it is harvested at mature but unripe stages and stored at low temperatures. The goal of this work was to study the influence of harvest and chilling storage of mature green tomato fruit (cv. Micro‐Tom) on the protein pattern, amino acid content and protease activity during fruit ripening. RESULTS: Fruits were sampled during ripening in three different conditions: 1, on the vine; 2, off the vine; 3, off the vine after 4 weeks at 4 °C. During all fruit ripening conditions, protein level decreased while amino acid content increased. Chilling storage of mature green fruit led to a reduction in protein content. Ripening off the vine (conditions 2 and 3) resulted in a threefold increase in red fruit amino acid levels when compared with red fruit on the vine. Protease activities (autoproteolytic, azocaseinolytic and gelatinolytic) were detected in all fruits evaluated and were differently affected by ripening stage, ripening conditions and the presence of specific inhibitors. CONCLUSION: Harvest and chilling storage increased endogenous substrate proteolysis, azocaseinolytic activity and free amino acid levels, which could be related to fruit quality. Copyright © 2011 Society of Chemical Industry     

Electrical stimulation and ultra-rapid chilling of pork

Six pigs were stimulated at 5 min post mortem and six remained unstimulated. All the pigs were split hot and one side from each pig was rapidly chilled in two stages (air at -40°C and 1 m/s for 80 min followed by 0°C and 0·5 m/s for 130 min) and the other side was conventionally chilled (air at 0°C and 1 m/s for 24 h). The weight loss from rapidly chilled sides was approximately 1% less than that from conventionally chilled controls. Cooked samples of Longissimus dorsi were tougher from unstimulated rapidly chilled sides (0·23 J) than from unstimulated conventionally chilled sides (0·18 J), whilst samples from both stimulated treatments were significantly more tender (0·15 J). These differences in toughness are thought to be due to a combination of cold shortening and lack of conditioning. The average pH in the longissimus dorsi of both rapidly and conventionally chilled stimulated sides at 50 min post mortem was 5·57 and samples from these muscles were slightly paler and more watery than the unstimulated controls.     

Blast chilling and low voltage electrical stimulation influences on bison (Bison bison bison) meat quality

Conventional carcass chilling is a lengthy and energy expensive process. Blast chilling (BL) can reduce cooling time and associated shrink loss, although its application may compromise meat quality, particularly in lean carcasses or those with localized finish such as bison. Low voltage electrical stimulation (LVES) can reduce the risk of decreased meat quality by inducing rapid rigor onset prior to exposure of the musculature to extreme cold temperature. BL (−20°C, 3 m·s⁻¹ air velocity, 2 h) accelerated temperature decline of bison Longissimus lumborum (LL) and significantly reduced cooler shrink loss versus conventional chilling (CONV: 0–2°C, 24 h). While BL tended to produce darker meat, this effect was tempered by the application of LVES, and samples from the combined treatment were significantly lighter than CONV. BL resulted in reduced tenderness in the LL, as assessed by shear force measurement, in part due to significantly shorter sarcomere length in BL samples. Taste panelists, however, were unable to detect a significant or detrimental BL effect. Where LVES was incorporated, there was an improved tenderness response with ageing. The combined LVES/BL treatment of bison carcasses is recommended for rapid processing without compromising meat quality.     

Responses of different types of ox muscle to electrical stimulation

The effects of electrical stimulation on fall in pH upon stimulation (ΔpH), rate of pH fall (dpH/dt at 35°C, cold shortening and muscle ultrastructure were investigated for the Cutaneus trunci (predominantly fast-twitch glycolytic fibres), the Masseter and Diaphragm (predominantly slow-twitch oxidative fibres) and the Sternomandibularis and Longissimus dorsi (bot fast- and slow-twitch fibres) of the ox. The Masseter and Diaphragm showed a small ΔpH and no increase in dpH/dt upon stimulation. Stimulation produced supercontracture but no tearing of the fibres throughout all of the Masseter. Stimulation of the Cutaneus trunci resulted in a significantly increased ΔpH and dpH/dt, loss of glycogen, mitochondrial swelling but no gross sarcomere changes. The Longissimus dorsi and Sternomandibularis had a moderate ΔpH and an increase in dpH/dt intermediate between that of the Masseter and the Cutaneus trunci. The Longissimus dorsi showed supercontracture, but the Sternomandibularis did not. Cold shortening responses at 2°C and 0°C were virtually unaffected by stimulation, being greatest in the Masseter and Diaphragm and least in the Cutaneus trunci. All muscles showed significantly greater shortenings at 0°C than 2°C. Stimulation of the Cutaneus trunci did not affect the tenderness of the cooked meat, but the toughness increased dramatically in cold-shortened Cutaneus muscle, regardless of stimulation. The Cutaneus trunci least requires stimulation as it does not cold shorten appreciably and therefore early rigor would confer no advantage. The Masseter and Diaphragm have a fast dpH/dt and therefore would enter rigor early. Mixed muscles apparently have the combined, least desirable characteristics of the muscle fibre types-i.e. their rate of rigor development is slow and they cold shorten. Electrical stimulation confers a significant advantage by mitigating these mixed-muscle characteristics in carcass muscles.     

Effect of low-voltage electrical stimulation after dressing on color stability and water holding capacity of bovine longissimus muscle

The effect of low voltage electrical stimulation after dressing (ES) on color stability and water holding capacity (WHC) of beef was investigated. Nine Swedish red cattle were slaughtered and the left side was electrically stimulated (80 V, 35 s) approximately 30 min after stunning, whereas the other side was not treated and used as control. Color and its stability, WHC, and protein solubility were evaluated on longissimus lumborum muscles from the two sides. ES produced a brighter red color at 24h mainly by increasing the oxygenation capacity of myoglobin (P<0.01), which was attenuated by postmortem aging. ES did not affect WHC, protein solubility and color stability (P>0.05). Therefore, this technology could accelerate meat tenderization without any negative effect on commercial attributes, such as color or drip of bovine longissimus muscle.     

Changes of the fatty acid composition and malondialdehyde concentration in rabbit Longissimus dorsi muscle after regular electrical stimulation

The experiment was carried out to investigate, whether in vivo transcutaneous electrical nerve stimulation (TENS) affects the fatty acid composition and antioxidant status of rabbit Longissimus dorsi muscle. Altogether 20 Pannon White meat type rabbits were divided into two groups, from which one was routinely exposed to TENS treatment with the following settings: 2 events (each 20 min) a day/50 days, 1 channel (2 electrodes)/animal, 30 Hz, 20 μs impulse length and 10 mA. The control group was not treated. After slaughtering gas chromatography analysis of the muscle showed significantly decreased stearic, arachidonic and docosahexaenoic acid proportions, while the estimated activity of the elongase enzyme decreased. The malondialdehyde concentration decreased insignificantly in the treated group, however, it followed the changes of the total highly unsaturated fatty acid amount (three or more double bonds), which decreased from 9.16% to 7.81%. The adaptation to the in vivo electrical treatment may significantly influence the meat fatty acid profile, especially PUFA proportion.     

Effect of electrical stimulation and temperature on biochemical changes in beef muscle

The effect of low voltage electrical stimulation and storage temperatures of 2, 15 and 25°C on biochemical changes in M. sternocephalicus from beef carcasses was studied. It was shown that electrical stimulation accelerated the glycolytic processes resulting in an immediate increase in muscle lactate and about 30% reduction in ATP. Combination of stimulation and 15 or 25°C temperature further increased the changes with ATP, reaching 2 μM/g muscle in about 2 h post mortem. At 2°C, the biochemical changes were slow. By ensuring that the muscle temperatures in low voltage stimulated carcasses do not fall below 15°C for 2 to 3 h, this should provide favorable conditions for depletion of ATP and glycogen and the prevention of cold shortening at chilling.     

鱼腥草风味牛肉干生产工艺的研究

本试验主要以鱼腥草,新鲜牛肉为主要原料.研究了不同用量的鱼腥草、复煮时间和烘干时间对牛肉干品质和风味的影响.实验结果表明:鱼腥草和牛肉用量比为3:10,复煮时间为35min,烘干时间为6h,所制得的鱼腥草风味的牛肉干的品质最好.     

电刺激和延迟冷却对宰后牛肉肌原纤维蛋白降解变化的影响

本文研究了电刺激和延迟冷却对中国杂交黄牛宰后肌原纤维蛋白降解变化的影响.分析了宰后成熟0,3,7,10天时肌原纤维小片化指数的变化,并利用蛋白免疫印迹分析了肌间线蛋白Desmin和伴肌动蛋白Nebulin的降解情况.结果表明:电刺激和延迟冷却提高了肌原纤维小片化的程度,促进了Desmin和Nebulin的降解,缩短了成熟时间.     

Cold shortening capacity and beef muscle growth

Cold shortening capacity is related to animal growth. For unloaded strips of beef sternomandibularis muscles the degree of cold shortening developed at 2 °C during the pre-rigor period increased from approximately 0.2 for small young calves to 0.6 for large old bulls. This growth-dependent capacity to cold shorten is even more pronounced in muscle strips shortening isometrically. Thus in terms of power development, it increases forty-fold with the growth of beef sternomandibularis muscles to their mature sizes. In contrast, temperature sensitivity of the phenomenon is virtually the same for both small and large animals with the tendency to cold shorten declining in both to zero at 35 °C. These findings are important to meat chilling since they imply that cold shortening will be more pronounced the larger the carcass. This is offset to a degree by the fact that large carcasses will chill more slowly than smaller carcasses.     

Proteome changes in the insoluble protein fraction of bovine Longissimus dorsi muscle as a result of low-voltage electrical stimulation

Changes induced by low-voltage electrical stimulation (ES; 0-95 V for 8 s; 95 V for 32 s) in the insoluble protein fraction of bovine longissimus dorsi (LD) muscle at 1 and 24h post-ES were investigated by proteomics. Protein abundance patterns from ten Norwegian Red (NRF) young bulls were compared, and significant changes due to ES were found by rotation test and partial least square (PLS) regression analyses. Five protein spots showed lower abundance in ES samples at both sampling times, and in addition, 10 proteins at 1 h post-ES and 13 proteins at 24 h post-ES changed significantly in abundance due to ES. Reduced abundance of full-length structural proteins in ES samples indicates an accelerated proteolysis due to ES. Moreover, increased abundance of small heat shock proteins indicates earlier initiation of stress responses due to ES. These findings provide a better understanding of the biochemical processes taking place as a result of ES during post mortem storage of meat.