Establishment Of Analytical Method Of Seafood Quality Based On Low Field Nuclear Magnetic Resonance Technology

Low field nuclear magnetic resonance(NMR) technology has been widely used in the fields of agriculture, oil chemical industry and food, etc due to its advantages of the rapid, non-intrusive, available samples within visualization image information, monitoring dynamic change process of the samples. Consumers love seafood because of its high nutritional value. However, the traditional detection methods were complicated and time-consuming, that cannot achieve real-time monitoring. In this study, low field NMR was used to study different kinds of dry sea cucumber and regions fresh sea cucumber, determine the water uptake and distribution, investigate the relationships between the NMR parameters and rehydration ratio, texture of lightly dried sea cucumber during rehydration processing. In addition, prediction models were developed for the simultaneous determination of the water and fat contents of intact small yellow croakers.The NMR signal obtained by Carr-Purcell-Meiboom-Gill(CPMG) sequence was processed by principal component analysis(PCA) to identify different kinds of dry sea cucumber and regions fresh sea cucumber. The results showed that low field NMR combined with PCA can distinguish lightly dried and salt dried sea cucumber, Lvshun and Xiaochangshandao fresh sea cucumber.The NMR and magnetic resonance imaging(MRI) were introduced to analyze presoaking and rehydration process of lightly dried sea cucumber. The water uptake and distribution during presoaking and rehydration process was monitored by NMR. The structure change was analyzed by MRI with T1 and T2 weighted imaging. The results indicated that the proper presoaking and rehydration time was 24 h and 96 h, respectively, for the lightly dried sea cucumber. Good linear correlation during the rehydrated process was observed between the NMR parameters and texture profile analysis parameters including the hardness, chewiness and rehydration ratio of lightly dried sea cucumbers.Small yellow croaker samples were measured by CPMG sequences and their water and fat contents were subsequently determined by drying and solvent extraction methods. The models were developed by combining low field NMR and principal component regression(PCR) or partial least squares regression(PLSR) to predict the water and fat contents in small yellow croaker samples. The results were very satisfactory because the correlation coefficients(R2) for the PCR and PLSR models were greater than 0.89. When using the raw magnetization decay data for PCR, the root mean square errors of cross-validation(RMSECV) were 0.7165 g and 0.1593 g for water and fat, respectively. The RMSECV of PLSR for water and fat were 0.7132 g and 0.1512 g, respectively. The results demonstrated that NMR was a rapid and accurate method for simultaneous determination of the water and fat contents in intact small yellow croaker.A rapid, non-destructive and accurate method was established by low field NMR technology to analyze the quality of sea cucumber and small yellow croaker in this study. It will provide the theoretical basis for the process of the seafood.