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Repeated freeze–thaw cycles can directly cause the changes in the water distribution, physicochemical characteristics, and microstructure of Scomberomorus niphonius surimi. To improve the quality of S. niphonius surimi, the effect of water retention agents (phosphate and trehalose) was investigated during freeze-thaw cycles. The results of low-field nuclear magnetic resonance (LF-NMR) combined with magnetic resonance imaging (MRI) analysis showed that the water retention agents could obviously decrease the water loss and water mobility during repeated freeze–thaw cycles. Water retention agent significantly reduced the cook loss and improved the surimi quality by decreasing the surimi protein denaturation. The scanning electron microscopy (SEM) characterization revealed that water retention agents could obviously ameliorate the protein structure damage. In addition, the principal component analysis combined with LF-NMR parameters showed clear discrimination between samples supplemented with different water retention agents. In a word, the LF-NMR and MRI might provide useful information in a non-invasive manner for monitoring the effects of water-retention agents on surimi after repeated freeze–thaw cycles. [ABSTRACT FROM AUTHOR]

Identification of edible oil adulteration is an essential task for oil quality control. In this study, the adulteration of sesame oil samples with soybean oil was detected by low-field nuclear magnetic resonance (LF-NMR) combining with chemometrics including principal component analysis (PCA), partial least squares (PLS) and principal component regression (PCR) methods. PCA analysis was applied for the classification of various adulteration ratios of sesame oil samples. PLS and PCR were used for the detection of adulteration ratios of sesame oil samples. A calibration data set was established and evaluated by a cross-validation method. The correlation coefficients between actual and predicted values for the calibration and validation data sets were 0.953 and 0.973 for PLS and 0.975 and 0.979 for PCR, respectively. Therefore, a combination of LF-NMR with chemometrics can be applied for detecting sesame oil adulteration in a fast and nondestructive manner. [ABSTRACT FROM AUTHOR]

Mung bean sprouts are a kind of favorite healthy food across the world. As a forbidden plant hormone cytokinins, the use of 6-benzylaminopurine (6-BAP) in promoting the growth of bean sprouts is forbidden due to its safety concerns. Rapid analysis of 6-BAP treated bean sprouts is required to assess their growth changes and discriminate them from the normal sample. In this study, the water dynamics of growth for 6-BAP treated bean sprouts was monitored by the low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging. A simplified cartoon model of the water dynamics was proposed to explain the LF-NMR analysis result. Principal component analysis of the NMR relaxation data clearly showed the different water distribution of 6-BAP treated bean sprouts from the control sample. The juice of 6-BAP treated bean sprouts showed significant difference in the ultraviolet absorption and fluorescence spectra. Therefore, combining the spectrometry, the LF-NMR may have potential for rapid discrimination of the 6-BAP treated bean sprouts. [ABSTRACT FROM AUTHOR]

Apple jam is one of the favorite foods consumed worldwide. This study investigated the effect of storage time and sugar concentration on water dynamics in Fuji and Yinduqing, using low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques. The samples were taken for jam preparation with various concentrations of sugar solution (0, 25, 50 and 75-oBrix) and stored at a room temperature of 20 °C for 16 days. The LF-NMR relaxation time T2 distribution displayed bound, intermediate and free water, respectively. The lowest T2 range reflected lowest sugar hydrogen mobility depending on total soluble solids (TSS) and water content. A significant correlation (r > 0.9) existed between LF-NMR analysis and physicochemical parameters (water content, color, pH and TSS). MRI displayed uniform water distributions in samples with low sugar concentration. Fluorescence microscopy was used to evaluate sugar crystals and microstructural changes during processing. The study demonstrated the viability of LF-NMR method in determining water dynamics in the apple jams upon processing and storage that may be implemented for quality analysis in other jam products. [ABSTRACT FROM AUTHOR]

Turbot is a valuable commercial species due to its high nutrient content. Moisture is an important indicator of meat spoilage. This study elucidated distinctive water dynamics in turbot flesh in the freezing-thawing process by nondestructive low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques. T2 relaxation spectra were utilized to describe the mobility and content of different types of water. Principal component analysis (PCA) revealed a clear discrimination of various freezing-thawing cycles. T1- and T2-weighted MRI provided further visualization of internal information for turbot flesh. Microscopic examination clearly identified protein denaturation and structural shrinkage. Furthermore, NMR parameters and conventional physicochemical parameters of color, shear force and thiobarbituric acid-reactive substances showed good correlations. To sum up, the study revealed that LF-NMR and MRI are promising techniques to portray the relationship between the water dynamics and changes of turbot quality properties during the freezing-thawing process. [ABSTRACT FROM AUTHOR]

Turbot is a valuable commercial species because of its high nutrition content. Water redistribution during heating was attributed to temperature-induced protein denaturation and structural shrinkage. Therefore, knowledge about water dynamics provides valuable information related to flesh physical properties (weight loss, color and shear force). Herein, water dynamics in turbot during baking and microwave heating were elucidated by using low field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI). Four distinct water populations with relaxation times of 0.20-0.60 ms, 2.00-6.00 ms, 30.00-60.00 ms, and 250.00-560.00 ms were identified. The dramatic variation of water populations during baking and microwave heating indicated protein denaturation and structural shrinkage, which was further verified by MRI and microscopic examination. Furthermore, good linear correlations were observed between NMR parameters and weight loss, color and shear force. The results revealed that the water mobility and distribution in turbot provided valuable information for quality analysis during baking and microwave heating. [ABSTRACT FROM AUTHOR]