JIA-2019-11

2648 WANG Hao et al. Journal of Integrative Agriculture 2019, 18(11): 2644–2651 and enzymes removes immigrated free water by binding it to become bound water. Changes in the relative proportions of different moisture forms (free water and bound water) were observed in fresh ear corn during one-week storage at room temperature (Fig. 5). The trend of change in total water content in fresh ear corn during storage corresponded to the total signal intensity, and the varying currents of bound water and free water were reflected in the attenuation of the peak area. Similar to the total water content, the signal intensities of both bound water and free water attenuated too during storage, which reflected the process of dehydration in fresh ear corn. Significant decreases of the contents of free water and bound water were frequently observed, respectively, and significant reductions of total water content were consistently detected with each one-day increment of storage time (Fig. 5). Concentrations of carbohydrates including glucose and fructose increased as free water migrated into bound water. Nonetheless, with increase in the storage time, starch synthesis was more obvious than amylohydrolysis. The rate of net loss was lower in bound water than in free water because the percentage of bound water out of the total water generally showed a trend of increase (Fig. 5). 3.4. Daily analysis of moisture maps Borompichaichartkul et al . (2005) captured MR images within corn kernels to characterize the physical state of water in frozen corn during the freezing process. They found that the brighter areas of MR images corresponded to the locations with higher proton mobility, which indicates the existence of higher free moisture content. As shown a b c d de e 100.00 120.00 140.00 160.00 180.00 200.00 220.00 240.00 260.00 280.00 0 1 2 3 4 5 T 2 (ms) Time (h) Time (h) Time (h) Time (h) Time (h) Time (h) T 2 a bc c bc b bc 3500.00 3600.00 3700.00 3800.00 3900.00 4000.00 4100.00 0 1 2 3 4 5 A A d c a b bc b 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0 1 2 3 4 5 T 21 (ms) T 21 a c d c b c 300.00 400.00 500.00 600.00 700.00 800.00 900.00 1000.00 0 1 2 3 4 5 A 1 A 1 a b c d e f 150.00 200.00 250.00 300.00 350.00 0 1 2 3 4 5 T 22 (ms) T 22 a a a a a a 2000.00 2200.00 2400.00 2600.00 2800.00 3000.00 3200.00 3400.00 3600.00 0 1 2 3 4 5 A 2 A 2 Fig. 2 Changes in moisture relaxation time and semaphores in fresh ear corn at different storage time. T 2 , the relaxation time; T 21 , before 1 ms-transverse relaxation time of free water; T 22 , after 1 ms-transverse relaxation time of bound water; A, A 1 and A 2 , corresponded to the signal intensity of proton intensity of total water, free water and bound water, respectively. Means in each graph followed by the same letter are not significantly different at P =0.05 according to the Fisher’s protected least significant difference test. Bars are SD.