Assessment Of Water Mobility In Surf Clam And Soy Protein System During Gelation Using Lf-Nmr Technique

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-2 relaxation times for the SP-MP system. The first component, (T-21), was assigned to the highly integrated water located in protein macromolecules with a relaxation time of approximately 1.15 ms. The second signal, T-22, 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-23, with a relaxation time of around 100 ms was ascribed to the extra-myofibrillar water. With an increase in temperature, T-24 appeared which was assigned to the free water within the extra-myofibrillar space. The gelation behavior occurred at 70, 62, and 52 degrees 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 tan delta 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 degrees 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.