延迟冷却对牛肉品质影响的研究

研究了常规冷却和延迟冷却对中国杂交黄牛(鲁西黄牛×西门塔尔)宰后冷却过程中牛胴体pH、温度的变化、胴体冷却失重、背最长肌汁液损失、蒸煮损失、保水性、肉色及成熟过程中剪切力值的变化。结果表明:延迟冷却减缓了牛胴体温度的降低速率(P<0.05),加快了牛胴体pH的降低(P<0.05);延迟冷却提高了牛背最长肌的嫩化速度,改善了肉色(P<0.05),但增加了汁液损失和蒸煮损失,降低了保水性(P<0.05)。因此,优化延迟冷却程序是必要的。     

冷却牛肉贮藏过程中的品质变化

分析冷却牛肉贮藏过程中各品质指标的变化,确定理化指标和微生物指标的相关性,为提高牛肉的品质提供依据。文中测定了4℃贮藏的冷却牛肉在0、2、4、6、8、10、12、14 d的菌落总数、嗜冷菌总数、pH值、挥发性盐基氮、失水率、色差值,确定了各指标随保存时间的变化规律及其相关性。结果表明:在贮藏过程中,pH值呈现先下降后上升的趋势;挥发性盐基氮呈上升趋势;系水力逐渐下降;肉色a值、DE(d ifference error)值不断降低。在品质变化的各指标中,微生物菌落总数、嗜冷菌总数与pH值呈正相关,且差异显著(P<0.05);菌落总数与系水力、a值呈负相关性,差异显著(P<0.05)。其中菌落总数与挥发性盐基氮、a值的相关性较大且极显著相关(P<0.01)。由此可知,微生物的活动能引起牛肉理化指标的变化,通过测定挥发性盐基氮和a值可以客观反映冷却牛肉的微生物污染状况。     

真空冷却与常规冷却方式对白煮牛肉品质影响的比较

本实验研究了真空冷却方式与冷风冷却,自然冷却方式对白煮牛肉品质的影响。样品中心温度从80℃冷却到10℃以下,与冷风冷却(120min)室温冷却(240min)相比较,真空冷却(24min)冷却速率较高。与常规冷却方式相比较,真空冷却的冷却损失较高,剪切力较大,硬度较大,弹性较低,色泽较差。感观分析表明,真空冷却样品总体可接受性不及常规冷却样品。微生物检测表明,真空冷却能显著降低菌落总数,减少细菌增殖,保证样品的卫生质量。     

冷却方式和电刺激对牛肉品质的影响

肉的嫩度是肉最重要的食用品质,它决定了肉的商品属性。动物宰前、宰后24h内的技术处理决定了肉的嫩度。本文主要综述了对牛屠宰后的处理方式如冷却方式、电刺激处理等对牛肉嫩度的影响。     

大豆分离蛋白-脂质涂层对冷却牛肉品质的影响

研究脂质(硬脂酸、棕榈酸、巴西棕榈蜡和三乙酸甘油脂)与大豆分离蛋白制成的可食性涂层对冷却牛肉品质的影响。考察冷却牛肉在4℃下贮藏108h过程中失重率、颜色、pH值、硫代巴比妥酸值和感官特性的变化。结果表明冷却牛肉在4℃贮藏时的货架期小于108h,而且在4℃贮藏84h后,不同大豆分离蛋白-脂质涂层的优点不同。其中,三乙酸甘油酯蛋白涂层不仅延缓冷却牛肉的氧化,而且有效维持其感官特性,对维持冷却牛肉品质和延长期货架期效果最佳。     

电刺激对牛肉成熟和牛肉超微结构的影响

对宰后牛胴体进行电刺激 ,跟踪检测牛肉在不同成熟时间的 p H值、剪切力值和超微结构的变化。试验结果表明 ,电刺激可加速牛肉成熟速度 ,提高牛肉嫩度 ,促使肌原纤维小片化 ,减少牛肉在预冷过程中发生的寒冷收缩     

气调包装对冷却牛肉色泽稳定性的影响

冷却肉的颜色是决定消费者购买行为的重要因素之一.本文用不同的气调成分0.5%CO/60.4%CO2/39.1%N2(CO组)、62.8%CO2/37.2%N2(无氧组)、69.9%O2/30.1%CO2(高氧组)和真空(真空组)包装冷却牛肉并在1±1℃下贮藏,结果显示,CO组在贮藏28天时仍色泽鲜红、鲜度仍在国标规定的范围内;高氧组在第一周色泽鲜红,第二周已发生褪色,并且有较强的脂肪氧化异味;无氧组和真空组处理的冷却肉在28天时虽然可保持鲜度在国标范围内,但此两组处理的色泽在28天时呈灰褐色或暗紫色,不是消费者所喜爱的鲜红色.     

宰后不同冷却方式对羊肉品质的影响

为了建立适宜的宰后羊肉冷却程序,采用不同冷却方式(常规冷却,0~4℃放置96 h);延迟冷却,(15±0.5)℃先冷却8 h,然后在0~4℃条件下冷却至96 h;高温冷却,(25±0.5)℃冷却2h,然后放置在0~4℃条件下继续冷却至96 h)对宰后羊肉进行冷却处理,研究不同冷却方式对羊肉品质的影响。研究结果表明:延迟冷却和高温冷却显著增加了羊肉的蒸煮损失率,降低了羊肉的剪切力值,提高了羊肉嫩度,缩短了羊肉的成熟时间(P<0.05);同时提高了羊肉的L^*值(P<0.05),增加了a^*值(P<0.05),使羊肉的色泽鲜红;此外高温冷却和延迟冷却提高了羊肉的羰基含量(P<0.05),降低了巯基含量(P<0.05),温度越高,羊肉蛋白的氧化程度越大;而且高温冷却的菌落总数显著高于常规冷却和延迟冷却(P<0.05),存在腐败的风险。试验结果证实延迟冷却和高温冷却对羊肉品质的改善均具有积极作用,但考虑微生物和蛋白氧化的因素,延迟冷却更适宜作为宰后羊肉冷却程序。     

气调包装对冷却牛肉货架期的影响

冷却肉的货架期直接影响着其销售情况。本文用不同的气调成分:0.5%CO/60.4%CO2/39.1%N2(CO组)、62.8%CO2/37.2%N2(无氧组)、69.9%O2/30.1%CO2(高氧组)和真空(真空组)包装冷却牛肉,并在1±1℃下贮藏。结果显示,CO组在贮藏28d时在保持鲜红颜色的同时,鲜度仍在国标规定的范围内;高氧组第一周可以保持颜色鲜红,但第二周已有较强的脂肪氧化异味,且颜色开始褐变;无氧组和真空组处理的冷却肉在28d时虽然可保持鲜度在国标范围内,但此两组处理的色泽在28d时呈灰褐色或暗紫色,不是消费者所喜爱的鲜红色。     

不同淀粉与大豆分离蛋白混合涂层对冷却牛肉贮藏品质的影响

研究淀粉（木薯淀粉、红薯淀粉、马铃薯淀粉、玉米淀粉、豌豆淀粉和高直链淀粉）与大豆分离蛋白混合可食性涂层对冷却牛肉贮藏品质的影响。研究在4℃下贮藏5d过程中,各种淀粉与大豆分离蛋白混合涂层对冷却牛肉失重率、颜色、pH、硫代巴比妥酸值和感官评价得分的影响。结果发现豌豆淀粉和玉米淀粉与大豆分离蛋白混合涂层不仅有效降低冷却牛肉中水分损失（分别为9.97%和12.83%,低于聚乙烯膜包装）,而且较好的保持冷却牛肉的感官指标。     

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.     

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.     

Effect of very fast chilling and aging time on ultra-structure and meat quality characteristics of Chinese Yellow cattle M. Longissimus lumborum

Objectives of the current study were to evaluate meat ultra-structure and tenderness variation at different chilling regimes and aging times. Hot boned longissimus lumborum of 18 Chinese crossbred cattle were divided into 4 portions per side. One portion underwent very fast chilling (VFC, at -21°C to achieve core temperature of 0°C, then transferred to another incubator at 2°C), whereas other treatments were held at 14, 7 and 0°C for 10h postmortem, respectively. At 10h postmortem, all muscles were vacuum aged at 2°C for 21d. Cold shortened muscles had greatest absolute amount of tenderization during aging. VFC caused lowest sarcomere length, with super-contractions, ruptured Z-lines and myofibril cleavage, but improved myofibril fragmentation index (MFI), with no significant negative effect on toughness. Overall, aging improved the meat quality of cold shortened beef. Moreover, it should be prudent in some applications to apply VFC to excised muscles from a food safety perspective, and to improve tenderness compared to cold-shortened muscles.     

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.     

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.     

宰后放置时间对牛肉匀浆物热诱导凝胶特性的影响

通过对宰后1、2、3、4、5d的牛肉匀浆物的可溶性蛋白质浓度、凝胶的保水特性、凝胶强度及质构特性等指标的测定,研究宰后放置不同时间对牛背最长肌匀浆物热诱导凝胶特性的影响。结果表明,匀浆物的蛋白质浓度与凝胶保水性随放置时间呈现相同的先降后升的变化趋势,而凝胶强度、脱水率、硬度、粘性与咀嚼性则呈现相反的先升后降趋势。宰后放置时间较短时(1~3d),凝胶弹性呈现先升后降的显著变化,当放置较长时间(≥4d),弹性值有所回升,但变化并不显著。宰后放置较短时间(1~3d),内聚性随宰后时间的增加显著降低,宰后放置较长时间(≥4d),内聚性增加并趋于稳定。由此可知,宰后放置不同时间对牛肉匀浆物的凝胶特性影响较大,且各指标随宰后时间的变化趋势存在明显的相关性,可为凝胶类肉制品生产的原料选择提供理论依据。      

Effect of high pressure and salt on pork meat quality and microstructure

The interaction of salt (0%, 1.5%, and 3% in the final product) and a high-pressure treatment (500 MPa, 20 °C, 6 min) was investigated using pork biceps femoris muscle. The Warner-Bratzler shear force and the water holding capacity (WHC) were assessed and linked to the microstructure evaluation by environmental scanning electronic microscopy (ESEM). Pressure-treated and cooked samples showed a high Warner-Bratzler shear force with a low WHC compared to control cooked samples. These negative effects could be linked to the general shrinkage of the structure as observed by ESEM. The addition of 1.5% salt was sufficient to improve the technological properties of the high-pressure-treated samples and to counteract the negative effect of high pressure on texture and WHC. This phenomenon could be linked to the breakdown in structure observed by ESEM. This study states that it is possible to produce pressurized pork products of good eating quality by adding limited salt levels.     

包装材料阻隔性对牛肉冷藏保鲜效果的影响

为研究包装材料阻隔性对牛肉在0⁴℃贮藏期间品质的影响,采用EVA/PE、PET/CPP、PVDC/PE3种阻隔性材料对牛肉进行真空和热收缩包装,并对牛肉菌落总数、挥发性盐基氮（TVB-N）、色差值（L*、a*）、持水力、剪切力、质构等指标进行跟踪分析。结果发现:中阻隔和高阻隔组显著抑制包装袋中微生物的生长和TVB-N值的升高,中阻隔和高阻隔组在货架期上要高于低阻隔组14 d。各处理组的亮度值L*显著增加（p<0.05）,红度值a*差异不显著（p>0.05）。高阻隔组的持水力大于中阻隔和低阻隔组,而各组剪切力显著下降（p<0.05）。研究表明高阻隔材料可有效延缓牛肉品质劣变,延长牛肉的货架期。      

Effect of 1-methylcyclopropene on chilling injury and quality of peach fruit during cold storage

The effects of different concentrations (0, 0.1, 0.5, 1, and 5 μL/L) of 1-methylcyclopropene (1-MCP) on chilling injury (CI), fruit quality, and antioxidant enzyme activities in cold-stored peach fruit (Prunus persica Batsch cv Baifeng) were investigated. The results showed that treatment with 0.5 μL/L 1-MCP significantly alleviated CI symptoms, including internal browing (IB) and flesh mealiness (FM), and maintained higher fruit quality. In addition, 1-MCP inhibited the activities of polyphenol oxidase (PPO) and peroxidase (POD), maintained higher activities of antioxidant enzymes and kept the balance of the polygalacturonase (PG)/pectinmethylesterase (PME) ratio. The treatment of 1-MCP markedly inhibited the increase of electrolyte leakage and the accumulation of malondialdehyde and hydrogen peroxide. Thus, 1-MCP (0.5 μL/L) treatment is effective in preventing CI and maintaining overall quality in peach fruit. The effect of 1-MCP on alleviating CI may be due to its capability to enhance antioxidant enzyme activities and to reduce oxidative damage. Practical Application: Treatment with 0.5 μL/L 1-MCP significantly prevented chilling injury and maintained fruit quality in "Baifeng" peaches. In addition, 1-MCP could enhance antioxidant enzyme activities and alleviate oxidative damage. Thus, 1-MCP has the potential for application in the Asiatic peach industry.