【作者】 戴妍；

【导师】 戴瑞彤；

【作者基本信息】 中国农业大学 ， 农产品加工及贮藏工程， 2014， 博士

【摘要】 本实验研究了欧姆加热或解冻肉块到一定终点温度下肌浆和肌纤维蛋白降解、氧化、色泽、嫩度,营养品质等方面的影响,同时也研究了欧姆加热肉糜凝胶特性。具体的研究结果和结论如下：通过比较欧姆加热与水浴加热肉块到一定的终点温度(10℃-80℃)时肉品色泽与肌浆蛋白等参数的变化影响。结果表明：当肉块的终点温度为(60℃-80℃)时,欧姆加热处理组的亮度值、黄度值、去氧肌红蛋白含量以及高铁肌红蛋白含量显著低于(P<0.05)水浴加热处理组。当肉块的终点温度超过40℃时,欧姆加热处理的肉块的肌浆蛋白含量(5.97mg/g vs.14.89mg/g)和保水性能显著低高于(P<0.05).水浴加热处理的肉块。与欧姆加热处理组相比,水浴加热处理组肉块的肌浆蛋白质电泳条带发生了更为明显的弱化现象。欧姆加热处理的肉块亮度、黄度,高铁肌红蛋白含量以及可溶性蛋白质含量有较强的相关性。通过比较欧姆加热与水浴加热肉块到一定终点温度(20℃-100℃)时剪切力、蛋白质降解、肌纤维结构、氧化、蛋白质表面疏水活性,蛋白质聚合以及蛋白质的体外消化率等参数的变化影响。结果表明：当肉块的终点温度范围为(20℃-80℃)时,欧姆加热处理组肉块的蒸煮率损失与剪切力显著低于(P<0.05)水浴加热处理组肉块,而可溶性蛋白质含量,pH以及蛋白质的相变温度显著高于(P<0.05)水浴加热处理组。欧姆加热处理组肉块肌纤维蛋白电泳条带发生了轻微的弱化现象,其肌纤维收缩和Z线结构消失的现象并不如水浴加热处理组那样明显。欧姆加热处理组的肉样中pH、蒸煮率损失、剪切力,肌浆蛋白含量以及蛋白相变温度之间呈现出较好的相关性。当肉块的终点温度为(40℃-100℃)时,欧姆加热的肉块中TBARS、羰基值以及蛋白质表面疏水活性显著低于(P<0.05)水浴加热处理组肉块。当肉块的终点温度为(80℃-100℃)时,欧姆加热与水浴加热处理组肉块的蛋白质体外消化率无显著性差异(P>0.05)。欧姆加热肉块的蛋白质聚合度与胃蛋白酶体外消化率呈现显著的负相关关系(P<0.01),而胰蛋白酶体外消化率与其他指标之间无显著相关性(P>0.05)。通过比较欧姆加热和水浴加热肉制品在4℃、7天储藏时间中脂肪、蛋白质氧化、非血红素铁含量,颜色以及质构的差异性影响,结果表明：储藏时间和加热方式显著影响(P<0.05)欧姆加热与水浴加热肉制品颜色、质构,脂肪氧化以及蛋白羰基含量。欧姆加热的肉制品具有较好的颜色和脂肪氧化稳定性,由于其蛋白质氧化程略高,这样可能引起肉质变硬。通过比较欧姆加热和水浴加热,加入或不加入0.5%TG酶时肉靡凝胶特性的差异性变化的影响,结果表明：在加入0.5%TG酶的前提下,欧姆加热的肉糜凝胶比其他处理组有较强的破碎力、凝胶强度以及更为密集的凝胶网状结构(P<0.05)。因此在引入0.5%TG酶的基础上,欧姆加热可以加工出与传统水浴加热相仿的肉靡凝胶制品。通过比较欧姆解冻和水浴解冻肉品(把肉块从-18℃解冻到4℃)的基本理化指标、颜色、总色素蛋白含量、可溶性蛋白质含量、肌原纤维蛋白小片化指数、蛋白质的差热扫描、肌浆蛋白与肌纤维蛋白的SDS-PAGE分析,脂肪与蛋白质氧化以及肌纤维组织结构的差异性变化影响,结果表明欧姆解冻肉块的a*值显著高于(P<0.05)水浴解冻组,而高铁肌红蛋白含量和肌原纤维蛋白小片化指数较低(P<0.05)。更多还原

【Abstract】 This study was designed to track the changes of protein degradations, oxidations, colour, texture, nutritional qualities of pork longissimus dorsi at a certain endpoint temperature (EPTs) during ohmic cooking or thawing. Meanwhile, functional properties of heat-induced gels during ohmic cooking were also evaluated, The specific contents and results are as follows:The objective of this study was to investigate the effects of ohmic (OH) and waterbath (WB) cooking on colour attributes and sarcoplasmic protein changes of porcine longissimus dorsi muscle at the same endpoint temperatures (EPTs; range10℃-80℃). The results showed that lightness (L*) and browness (b*) values, deoxymyoglobin%(DeoMb) and metmyoglobin%(MetMb) of the OH-cooked meat were significantly lower (P<0.05) than those obtained by WB-cooking at the same EPTs (range60℃-80℃). SDS-PAGE analysis showed that the meat treated with WB-cooking had fainter protein bands, A higher sarcoplasmic protein solubility (5.97mg/g vs.14.89mg/g, P<0.05) and better waterholding capability were obtained in OH-cooked meat at EPTs above40℃. Strong correlations among lightness, browness, metmyoglobin%and soluble proteins were observed in meat following OH-cooking.The effects of ohmic (OH) and water bath (WB) cooking on changes of shear parameters, protein degradations, ultrastructure, lipid and protein oxidations, protein surface hydrophobicity, protein aggregation and in vitro digestion of pepsin, trpsin and a-chymotrypsin of porcine longissimus dorsi muscle at the same endpoint temperatures (EPTs; range,20℃-100℃) were investigated. The results showed that the cooking loss and warner-bratzler shear force (WBSF) of the OH-cooked meat were significantly lower (P<0.05) while protein solubility, pH and endothermic transition temperature were higher than those obtained by WB cooking at the same EPTs (range,20℃-80℃). Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that during OH cooking, the meat had slightly fainter protein bands than that of WB-cooked ones. Less obvious shrinkage of the sarcomere and loss in the structure of Z discs were detected especially in OH-cooked meat at EPTs (100℃). Strong correlations among pH, cooking loss, Warner-Bratzler shear force, sarcoplasmic protein solubility, Tmax2, and Tmax3were observed in meat following OH cooking.TBARS, carbonyl content, protein surface hydrophobicity of the OH-cooked meat were significantly lower (P<0.05) than those obtained by WB cooking at the same EPTs (range,40℃-100℃). No significant difference (P>0.05) in protein digestion in vitro between ohmically and waterbath-cooked meat. Results showed a direct negative relationship between pepsin in vitro and aggregation (P<0.01) in meat induced by ohmic cooking and proteolytic susceptibility to pepsin. However, no such correlations have been observed with trypsin and a-chymotrypsin in vitro (P>0.05). Changes in iipid and protein oxidation, non-heme iron (NHI) content, colour and texture parameters during refrigerated storage (7days/4℃) of ohmically (OH) and waterbath (WB)-cooked pork meat were studied. The results showed that a significant effect (P<0.05) of refrigerated storage duration and cooking method on colour, texture, Iipid oxidation and carbonyl content was detected OH-cooked and WB-cooked meat. The OH-cooked meat had better colour appearance, Iipid oxidative stability, slightly enhanced hardness and protein oxidation levels during7days of storage time, having lower values of TBARS, center lightness (L*), center/surface brownness (b*) and free thiol groups, whereas higher values of center/surface redness (a*), non-heme iron, protein carbonyl and hardness compared to those from WB-cooked meat.Gelation characteristics of pork batters, prepared in the absence and presence of0.5%transglutaminase (TG) were evaluated using either ohmic (OH) or water bath (WB) heating. The OH-cooked gels in the presence of0.5%transglutaminase exhibited higher breaking force, gel strength and a compact structure compared with other treated gel groups (P<0.05). The rapid heating method in the presence of0.5%transglutaminase could yield comparable or improved meat gels when compared to water bath heating.The frozen porcine longissimus dorsi muscle were thawed from-18℃to4℃during ohmic and conventional thawing treatments. The changes in the proximate, colour, total myoglobin and proportions of related pigments, soluble protein solubility and myofibrillar fragmentation index, differential scanning calorimetry for proteins, SDS-PAGE of sarcoplasmic and myofibrillar proteins, Iipid and protein oxidation as well as TEM of muscle ultrastructure of porcine longissimus dorsi muscle during ohmic thawing were compared with those during conventional thawing method. The results showed that The a*values in OH-thawed meat was significantly higher, whereas the MetMb%and MFI values were lower (P<0.05) than WB-thawed samples.更多还原