屠体预冷损耗控制概述

本文简述了国外科学家们为降低畜禽屠体预冷损耗,所采用的方法及其效果。这些方法包括用冰水浸泡、瞬间喷雾、高湿空气预冷来增加屠体表面湿度,用急速冷却、液氨浸泡缩短预冷时间,以及使用表面涂层的办法降低表层气流影响等。     

屠体预冷损耗控制概述

欧美屠宰行业很早就注意到，畜禽屠体在预冷过程中存在较大的水分蒸发损耗。例如，猪白条在预冷期间，若条件不恰当，在开始预冷的24h内，其预冷损耗可达到3％以上。早在20世纪70年代，国外科学家们便对屠体预冷过程中的损耗状况进行研究，他们发现降低预冷环境的温度，增加环境的相对湿度，减小屠体表面的循环风速，都能够有效地减少屠体预冷期间的重量损耗。     

降低冷鲜肉预冷损耗的研究

预冷损耗对于提高肉品质量,以及获得更好的经济效益具有重要的意义,本文就预冷间库温、预冷间湿度、风速对预冷损耗的影响进行了研究,探讨了合适的预冷工艺。     

冻片猪肉预冷结冻损耗试验

我厂以屠宰生猪为主,年宰杀生猪40～50万头,冷库二座6500吨。近几年来生猪放开后宰杀量减少到十万头左右。主要产品出口冻片猪肉,分割肉,罐头原料肉及供应大城市的冻片猪肉,年产2～3万吨。为了进一步了解生猪屠宰加工后,经预冷结冻过程中影响预冷结冻耗的因素,最终达到降低损耗,增加效益。厂里由生产技术科为主成立了试验小组,进行了测试,现将测试情况作如下介绍。     

真空预冷新鲜猪肉水分流失和DSC蛋白分析研究

从汁液流失和蛋白变性来探讨真空预冷与传统的预冷方式和不同的真空预冷终温对新鲜猪肉的影响.结果表明,真空预冷后猪肉的失水率高于其它的预冷方式,且真空预冷终温越低,失水率也越高;真空预冷的降温速度是-18℃冷库预冷的1.5倍左右,是0℃冷库预冷的3倍;真空预冷过程中其箱体内相对湿度的变化先经历了快速降低,然后缓慢上升,再迅速上升三阶段.不同的预冷方式对峰Ⅰ、峰Ⅱ、峰Ⅲ的变性焓值存在着显著性差异(P＜0.05).真空预冷至4℃峰Ⅰ、峰Ⅱ的变性焓值相对于其它的预冷方式更接近于新鲜猪肉.     

真空预冷复合可食性涂膜保鲜技术对新鲜猪肉品质的影响

通过不同的预冷方式及不同的涂膜方式对新鲜猪肉进行预处理,并将预处理后的猪肉置于(0±2)℃温度下的冷库中贮藏。同时,通过测定新鲜猪肉在贮藏过程中的理化、微生物指标来评价不同处理方式的优劣。结果表明,真空预冷复合可食性涂膜技术在防止水分损失、抗氧化及抑制微生物方面表现出极佳的正相关。无论在理化指标还是在微生物指标上都优于其他组。     

预冷温度对冰温罗非鱼片品质的影响

通过设置不同预处理温度(-18,-30,-60℃)对罗非鱼片进行预冷处理,使鱼片中心温度降至-1℃后置于-2℃环境中贮藏。以pH、色泽、质构特性、挥发性盐基氮(TVB-N)、菌落总数、硫代巴比妥酸值(TBA)、钙离子酶活(Ca~(2+)-ATPase)作为考察指标,进行不同时间间隔下的系列跟踪测试与分析。结果表明:预冷温度对鱼片的TVB-N值、菌落总数、TBA、Ca~(2+)-ATPase有较大影响,经过预冷处理鱼片的TVB-N值、菌落总数增长趋势有所减缓,并且预冷温度越低,鱼片细菌生长速率和鱼肉腐败的进程越慢,同时鱼片脂肪氧化和蛋白质变性的程度也相对较小,其中-30,-60℃预冷处理能更好地维持鱼肉的品质;贮藏期间各处理组鱼片的pH值整体表现出先下降后上升的趋势,预冷处理可显著抑制鱼片pH的回升。预冷处理组与对照组鱼片的硬度、咀嚼性和胶黏性均随贮藏时间推移呈下降趋势。-30,-60℃预冷处理鱼片的货架期为17d,比对照组延长了6d。综上可知,预冷处理能够进一步抑制鱼片微生物繁殖和腐败变质,改善冰温罗非鱼片的品质。     

预冷胴体的因子控制

德国食品专家Reusch先生认识，预冷胴体的品质变化由内在因子起决定作用。但通过外界因子的控制，可以对其变化产生一定的影响。主要方法有卫生质量控制和预冷因子的控制两大方面。     

不同预冷条件下白条损耗及菌落总数变化

以猪胴体为研究对象,研究不同冷却方式、湿度以及贮藏方式对猪胴体损耗的影响。结果表明,猪胴体在预冷库冷却24h,二段式冷却比一段式冷却水分损耗低0.1%~0.2%,菌落总数减少;白条在冷却过程中增加空气湿度,能使白条损耗降低约0.25%,但微生物菌落总数增加;白条套上保鲜袋能使白条水分损耗降低约0.2%,同样微生物菌落总数会增加。     

浅谈果蔬的几种预冷方式

预冷作为整个冷链环节中的第一环,它可使采后果蔬在进行冷藏运输之前,快速去除果蔬内部的"田头热",对维持果蔬品质方面发挥着极其重要的作用.现针对3类预冷方式:真空预冷、水预冷、空气预冷的特点进行对比和分析,为今后预冷技术的应用与发展提供一定的参考.     

猪胴体在预冷过程中的干耗研究

通过测定在0～4℃的预冷库环境中经24h预冷后三种猪胴体的干耗率,结果发现带皮白条干耗率>去皮白条干耗率>红条干耗率。通过在预冷过程中的重量变化可以看出,猪胴体在前2h的预冷过程中干耗量最大,然后干耗率逐渐降低。猪胴体干耗达到稳定猪红条耗时最短,带皮白条耗时最长。     

营养鸡排的研制

介绍了营养鸡排的生产方法,即通过混合、成型、速冻等工艺,生产重量为44g±1g/块的鸡排。     

The effect of stress during lairage and stunning on muscle metabolism and drip loss in Danish pork

The effect on meat quality of a low stress handling system (LSS) compared with a traditional handling system (TS) was investigated in Duroc×(Landrace×Yorkshire; n=117) and (Hampshire×Duroc)×(Landrace×Yorkshire) pigs (n=110) under commercial conditions. In the low-stress handling system the pigs were kept in groups of 15 during lairage and movement up to the stunner. Before the stunner the groups were divided into three groups of five pigs for the CO(2)-stunning in a specially designed set-up. The pH and temperature were determined in m. longissimus dorsi (LD) and m. biceps femoris (BF) at various times post mortem. Immediately after exsanguination a biopsy was taken from the LD and analysed for the concentration of glycogen, lactate and creatine phosphate. The day after slaughter the pH was determined in the LD, BF, m. semimembranosus (SM) and m. semispinalis capitis (SC). The temperature was determined in the LD and BF, the internal reflectance was determined in the LD, SM and BF, the colour was determined in LD, the drip loss was determined in LD and BF, and the amount of blood splashing/bruising was evaluated in LD. There was a tendency for a higher concentration of creatine phosphate in the LSS-group (P=0.06). The pH in both the LD and BF on the day of slaughter decreased more slowly from 5 min post mortem to 40 min post mortem in the LSS-group than in the TS-group (P<0.001). From 40 min to 6 h post mortem the rate of the pH decline was similar in the two groups producing the lowest pH-level in the TS group. The day after slaughter the pH was similar in the two groups in the LD and SC, whereas in the BF and SM it was lower in the LSS-group than in the TS-group. The drip loss was lower in the LSS-group in both LD (P<0.01) and BF (P<0.05) whereas the internal reflectance was only different in LD with the lowest value in the LSS-group (P<0.001). The lightness (L*) was higher in the LSS-group (P<0.05). There was no effect of stunning system on the amount of blood splashing/bruishing in the LD. The study showed that by using a low stress stunning system it is possible to decrease drip loss, possibly by increasing the concentration of creatine phosphate and thereby delaying the acceleration of pH fall in muscles after death.     

汉堡蔬菜鱼肉饼的研制

以鱿鱼、鳕鱼、胡萝卜和西芹为主要原料,研究了汉堡蔬菜鱼肉饼的工艺和配方。对鱼糜与鱼肉添加比例、蔬菜添加量以及淀粉和大豆蛋白添加量等影响因素进行研究,通过正交实验确定主要原料的最佳配方为:鱼糜与鱼肉添加比例6∶4,以鱼肉添加总量为基数,大豆蛋白添加量5%、淀粉添加量3%、蔬菜添加量7%。按上述方法制得的汉堡蔬菜鱼肉饼,颜色美观,状态均匀,营养丰富,味道甚佳。      

热鲜猪肉、普通冷却猪肉和真空包装冷却猪肉加工过程中品质变化研究

比较研究了热鲜猪肉、普通冷却猪肉和真空包装冷却猪肉在加工过程中胴体温度、pH值、肉色、食用品质(嫩度、风味、多汁性、喜好程度和总体评价)、微生物等的变化.结果表明,真空包装冷却猪肉的嫩度、风味、多汁性、喜好程度和总体评价都比普通冷却猪肉、热鲜猪肉好,真空包装延长了猪肉保质期,宰后成熟提高了猪肉的食用品质,真空包装冷却猪肉更受消费者青睐.     

银杏叶提取物控制草莓加工中VC损失的效应研究

研究了银杏叶提取物在草莓果实清洗、打浆等工序中控制VC 损失的效果 ,并且与食品加工中常用抗氧化剂EDTA、六偏磷酸钠、磷酸氢二钠进行比较。结果表明 :加入0 02 %～0 03 %的银杏叶提取物能有效地控制草莓果实加工中VC 损失 ,使VC 保存率提高52 19 %～72 47 % ,银杏叶提取物的抗氧化作用保护VC 免受破坏。     

挤压猕猴桃猪肉干维生素C损失预测模型研究

[目的]探索双螺杆挤压猕猴桃猪肉干中维生素C的损失规律,解决挤压过程中营养物质损失的“黑箱”问题。[方法]使用双螺杆挤压机生产猕猴桃猪肉干,采用高效液相色谱法测定物料挤压前后的维生素C含量,以平均停留时间作为物料在机筒内的反应时间,对不同挤压条件下维生素C损失率进行动力学分析。[结果]挤压过程中增大机筒温度和水分含量、降低螺杆转速和果干添加量会使挤出物维生素C损失率增大,平均停留时间与维生素C损失率变化规律基本保持一致,动力学分析表明挤压过程中维生素C损失遵循一级动力学模型,维生素C损失速率常数为0.003 54～0.006 05 s^-1。[结论]平均停留时间是影响维生素C损失率变化的重要原因,通过多元回归分析得到维生素C损失率的预测模型,可实现不同条件下维生素C损失率变化规律的合理预测,降低生产成本。     

Freezing and thawing rate effects on drip loss from samples of pork

The effects of six freezing rates, two storage times and three thawing rates on the drip loss from small samples (approximately 6 g) of pork were studied. Drip was collected by centrifugal extraction. Protein denaturation of the meat sample was analysed by differential scanning calorimetry. At fast freezing rates, drip losses obtained were not significantly different from that of fresh samples. At the slower freezing rates studied, drip losses were greater than that from fresh samples. After four weeks storage, drip losses were significantly greater at the slow freezing rates compared to the samples without storage. However, for the stored samples, there were no differences in drip losses with respect to the initial freezing rates. Furthermore, the drip losses from stored samples were not significantly different from drip losses of samples at the slow freezing rates without storage. No differences in denaturation profiles of the meat samples, composition of drip or total protein concentrations in the drip samples were observed.     

芒果压差预冷数学模型的建立

为了研究芒果预冷过程中的温度变化规律,建立了芒果中心温度在不同工况下的数学方程。通过对实验数据进行非线性回归分析,确定了冷风速度和模型系数之间的关系,得到了芒果温度随风速和时间变化的规律。所有方程的相关系数都在0.98以上,说明其可以很好的描述芒果预冷过程。