低温长时蒸煮对猪肉品质的影响

The Influence of Low-Temperature and Long-Time Cooking on the Quality of Pork Products

【目的】明确不同低温长时蒸煮条件对猪肉持水性、嫩度等食用品质的影响,从水分分布、肌纤维结构及胶原蛋白溶解方面揭示其潜在机理,为应用低温长时蒸煮加工猪肉提供理论基础。【方法】以猪背最长肌为试验材料,经不同低温(55℃和60℃)长时(4、8和24 h)加热处理后,检测蒸煮损失、体积收缩率、低场核磁共振波谱、氢质子成像、色差和剪切力,分析猪肉持水性、色泽和嫩度等品质特征;通过组织切片观察猪肉肌原纤维和结缔组织的变化,分析蛋白质表面疏水性和胶原蛋白含量及热溶解性变化。【结果】随着加热时间的延长与温度的升高,低温长时蒸煮处理对猪肉食用品质的影响逐渐增大,破坏肌纤维结构,增强蛋白质热变性程度,具体表现为:蒸煮损失显著增大(P<0.05),体积收缩变大,不易流动水T2弛豫时间左移(P<0.05),且含量显著减少(P<0.05)。b*值明显增大(P<0.05),肌原纤维收缩,肌内结缔组织逐渐溶解,肌纤维结构被破坏;蛋白质表面疏水性增大(P<0.05);胶原蛋白含量减少(P<0.05),溶解度增大。【结论】相对加热时间而言,加热温度对肉品食用品质和蛋白变性程度影响更为显著,延长加热时间可在一定程度上降低这种影响。加热温度不同,肉品的纵向收缩率变化更为显著,可能与不同温度下胶原蛋白尤其是不溶性胶原蛋白变性程度不同有关。

【Objective】The objective of this study was to investigate the effect of low-temperature and long-time(LTLT)cooking on water holding capacity(WHC)and tenderness of pork.It was expected to illustrate the potential mechanism for the change of moisture distribution,muscle fiber structure,and collagenolysis of the LTLT cooked pork,so as to provide a scientific basis for the actual industrial application.【Method】The pork Longissmus dorsi was used as experimental material which was boiled at different low-temperature(55℃and 60℃)for long-time(4 h,8 h,and 24 h)respectively.The quality characteristics of LTLT cooked pork,including WHC,color and tenderness,were analyzed by cooking loss rate,area shrinkage,low field nuclear magnetic resonance(LF-NMR),magnetic resonance imaging(MRI),color,and Warner-Bratzler shear force.The structural changes of myofibrils and connective tissue were observed by histological analysis.Then the surface hydrophobicity,collagen content,and its thermal solubility were analyzed.【Result】With the increasing of heating time and temperature,the influence of LTLT cooking on the quality of pork products and the protein denaturation increased.The muscle fiber structure was damaged during heating.Specifically,the cooking loss rate and area shrinkage ratio increased significantly(P<0.05);LF-NMR and MRI analysis demonstrated that the transverse relaxation time(T22)and peak area(A22)decreased markedly(P<0.05);the b*value increased(P<0.05).The shrinkage of myofibrils and collagen fibers in the perimysium dissolving occurred,the surface hydrophobicity enhanced significantly(P<0.05).The content of collagen decreased observably(P<0.05),while heat solubility increased.【Conclusion】Compared with heating time,heating temperature had more significant effects on meat quality and protein denaturation,and these effects could be alleviated by extending the heating time.At different heating temperatures,the difference in the longitudinal shrinkage ratio was more significant,which might be caused by different denaturation of collagen,especially the insoluble collagen.