Wang Siqi, Lin Rong, Cheng Shasha, Wang Zhixiang, Tan Mingqian
School of Food Science and Technology, Dalian Polytechnic University, Dalian 116034, China.
National Engineering Research Center of Seafood, Dalian 116034, China.
Foods. 2020 Feb 19;9(2):213. doi: 10.3390/foods9020213.
Water mobility and distribution of a dual-protein system of surf clam myofibrillar protein (MP) and soy protein (SP) was investigated by the nondestructive low field nuclear magnetic resonance (LF-NMR) technique. Four proton populations were found in the contour plots of T relaxation times for the SP-MP system. The first component, (T), was assigned to the highly integrated water located in protein macromolecules with a relaxation time of approximately 1.15 ms. The second signal, T, with a relaxation time of 2.20 to 38.00 ms was regarded as the inter-myofibrillar water trapped in organized protein structures. The third component, T, with a relaxation time of around 100 ms was ascribed to the extra-myofibrillar water. With an increase in temperature, T appeared which was assigned to the free water within the extra-myofibrillar space. The gelation behavior occurred at 70, 62, and 52 °C as the proportion of SP/MP was 4:6, 2:8, and 0:10, respectively. The principal component analysis (PCA) and heatmap of LF-NMR data analysis showed potential for distinguishing the different dual-protein systems formed at various temperatures. The analysis of storage modulus G', loss modulus G″, and tanδ confirmed the change trend of the LF-NMR results. The measurements of cooking loss, water holding capability, and gel strength further revealed that the SP and MP were likely to form a gel network with an increase of additional clam protein. The hydrophobicity analysis showed, for the systems with the SP/MP proportions of 4:6, 2:8, and 0:10, more hydrophobic groups were exposed when the temperature was over 50 °C. Scanning electron microscopy showed that the number of the micropores increased with an addition of MP in the dual-protein system of SP/MP. All the results demonstrated that LF-NMR has great potential for characterizing the gelation process of a dual-protein system.
采用无损低场核磁共振（LF-NMR）技术研究了缢蛏肌原纤维蛋白（MP）和大豆蛋白（SP）双蛋白体系的水流动性和分布。在SP-MP体系的T2弛豫时间等高线图中发现了四个质子群。第一个成分（T21）被指定为位于蛋白质大分子中的高度结合水，弛豫时间约为1.15毫秒。第二个信号T22，弛豫时间为2.20至38.00毫秒，被视为被困在有组织蛋白质结构中的肌原纤维间水。第三个成分T23，弛豫时间约为100毫秒，归因于肌原纤维外水。随着温度升高，出现了T24，它被指定为肌原纤维外空间内的自由水。当SP/MP比例分别为4:6、2:8和0:10时，凝胶化行为分别发生在70、62和52℃。LF-NMR数据分析的主成分分析（PCA）和热图显示了区分在不同温度下形成的不同双蛋白体系的潜力。储能模量G'、损耗模量G''和tanδ的分析证实了LF-NMR结果的变化趋势。蒸煮损失、保水能力和凝胶强度的测量进一步表明，随着缢蛏蛋白的增加，SP和MP可能形成凝胶网络。疏水性分析表明，对于SP/MP比例为4:6、2:8和0:10的体系，当温度超过50℃时，更多的疏水基团暴露出来。扫描电子显微镜显示，在SP/MP双蛋白体系中，随着MP的添加，微孔数量增加。所有结果表明，LF-NMR在表征双蛋白体系的凝胶化过程方面具有巨大潜力。
