## 3 Results and Discussion
### Measurements of LF-NMR  
LF-NMR undoubtedly provided excellent prospects in predicting of quality characteristics and shelf life of aquatic products. Previous researches demonstrated that there was a close relationship between transverse relaxation T\({}_{2}\) and traditional physicochemical parameters of the quality of muscle products [9]. Figure 2 showed the change trends of CPMG relaxation signal intensity at the beginning, middle, as well as the last stage of storage with different treatments. As mentioned in Figure 2, there was an obvious decreasing intensity in the curves with the storage time regardless of treated methods and no significant changes was not observed beyond 1000 ms of relaxation time. Meanwhile, the decreased rate of echoes of CK1 was higher than that of other treatments, especially samples treated with edible coating incorporated with 70% CO\({}_{2}\)/30% N\({}_{2}\) MAP. But [PERSON] et al. reported that the curves of signal intensity could rarely provide a descending trend of signal amplitude and reflect information about the status and distribution of different types of water [9]. In fact, the information obtained from CPMG echoes as raw date was limited, and further analysis needs to be carried out to fully explain the diversification of the three types of water. The multiexponential fitting of transverse relaxation T\({}_{2}\) distribution was carried out by Origin software and the protons associated with three types of water were identified. These results were consistent with some researches [14; 16]. As shown in Table 1, the shortest relaxation time T\({}_{21}\) in the range of 1.32-6.14 ms was detected, representing the bound water entrapped within tertiary and quaternary protein structures. Besides, the intermediate population of T\({}_{22}\) with a relaxation time of 28.48-117.38 ms considered as immobile water within the myofibril. Finally the third population, T\({}_{23}\) in the range of 403.7-3274.55 ms corresponds to free water extramoyofibrillar space [24]. Briefly, no significant differences were detected in T\({}_{21}\) time among different treated samples in the current experiment, indicating transverse time T\({}_{21}\) was not affected by treated methods as well as storage time. [PERSON] previously pointed out that T\({}_{22}\) diminished while T\({}_{23}\) increase with time in muscle [16]. But the conclusions disagreed with the results in the present study. Briefly, T\({}_{22}\) time of all samples fluctuated without regular trends; while T\({}_{23}\) firstly declined steadily and increased constantly. This fact was also indicated that the changes of free water were more obvious than those of bound and immobile water with the extension of storage time. Interestingly, the range of relaxation time for the three types of water was slightly different among all samples during storage, which may related to the migration of moisture during storage. This prediction is further verified by the changes trends of peak area proportion of certain type of water. Furthermore, the pT\({}_{21}\), pT\({}_{22}\), and pT\({}_{23}\) were corresponded to the areas of relaxation time T\({}_{21}\), T\({}_{22}\), and T\({}_{23}\). Obviously, pT\({}_{21}\) almost rarely changed during the entire storage period, ranging from 1.74 to 1.96. This behavior occurred due to the viewpoint that the water entrapped within highly organized myofibril structures and water in tertiary and quaternary protein structures were stable [25]. The pT\({}_{22}\) diminished progressively while pT\({}_{23}\) increased during storage, and pT\({}_{22}\) accounted for the largest proportion of three types of water, followed by pT\({}_{23}\).