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In this study, water mobility and oil qualities (color indexes, peroxide value, acid value, fatty acids) between continuous and intermittent hot air drying of fresh walnut were investigated based on LF-NMR technique and chemical assay. The results showed that intermittent drying of fresh walnut was comparable or superior to continuous drying, in view of drying rate, moisture ratio, energy saving, oil quality (L*, a*, b*, peroxide value, acid value, and fatty acids). LF-NMR relaxometry could be used for observing the moisture mobility and distribution of fresh walnut during tempering process. The R2 values of moisture prediction model were 0.9808 and 0.9702 for calibration and validation, respectively, exhibiting fine linear relationship between the T21 signals and moisture level. Meanwhile, principal component analysis showed that five geographical origins of dried walnut could be discriminated based on LF-NMR relaxometry. Thus, intermittent drying with tempering process was recommended in practice for fresh walnut drying, and LF-NMR technique could be used for moisture prediction and origin discrimination of dried walnuts. [ABSTRACT FROM AUTHOR]

Water status and distribution in shiitake mushroom and the effects of drying temperature on water migration were investigated by low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) technique. Three water components assigned to bound, immobilized water and free water were observed in fresh shiitake mushroom by LF-NMR, and higher moisture content was found in the lamella and outer layer of stalk by MRI. During drying, the transverse relaxation time and peak area of immobilized and free water in pileus significantly decreased. Higher drying temperature could promote the changes in water mobility and population. MRI results revealed the water evaporated from external surface of shiitake mushroom, then the water in inner region migrated to the surface during the drying. The drying properties, color and shrinkage of shiitake mushroom were also measured. The strong correlation between moisture content and total peak area of water with a coefficient of 0.9792 revealed the potential of LF-NMR as a rapid and nondestructive method to monitor drying degree of shiitake mushroom. [ABSTRACT FROM AUTHOR]

The dynamic states of water in shrimp during drying process were investigated by low-field nuclear magnetic resonance and magnetic resonance imaging. With the extension of drying time, the transverse relaxation time of immobilized and free water significantly decreased, illustrating their mobility reduced. The signal per mass of immobilized water also decreased significantly, indicating its remarkable loss during drying process. Magnetic resonance imaging results revealed that the water signal intensity decreased from the external surface to inner regions of shrimp. Good correlations between the moisture content, hardness, chewiness, cohesiveness, L*, a* and nuclear magnetic resonance T2 parameters were observed by linear regression analysis. [ABSTRACT FROM AUTHOR]

Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) were used to monitor the water mobility and distribution of Pacific oyster during drying process. The results show the mobilities of bulk, immobilized, and free water were reduced, and the immobilized water was removed dramatically.T2-weighted images displayed the water decrease from the external surface to inner center of oyster during drying. In addition, excellent correlations between the total moisture content andT22andA22were observed with coefficients 0.9777 and 0.9832, respectively. Principal component analysis showed the drying degree of oyster could be monitored based on raw relaxation data. Thus, the result revealed that LF-NMR and MRI have great potential in assessing water mobility and distribution in oyster during drying process. [ABSTRACT FROM AUTHOR]

To detect the water dynamics in abalone during drying is essential for the textural quality improvement, however, sufficiently rapid and nondestructive methods of abalone moisture monitoring are currently lacking. In this study, water changes in abalone during drying and rehydration processes were assessed using low field nuclear magnetic resonance and magnetic resonance imaging. A close correlation was observed between ATotal and the total moisture content, and a prediction model with high correlation (R2 = 0.935) was established. Furthermore, good correlations (R2 > 0.950) between hardness, chewiness, rehydration ratio, and T22 relaxation of dried abalone were observed during the rehydration process. [ABSTRACT FROM AUTHOR]