利用LF-NMR技术分析油桃干燥过程中内部水分的变化

为研究油桃内部水分分布及干燥过程中水分迁移规律,为油桃的保藏及加工提供新思路。利用LF-NMR技术测定了不同含水量油桃的信号强度与水分含量的关系及水分分布情况,并测定了不同干燥方式的油桃片横向弛豫时间(T2)的变化,进而分析了油桃内部水分状态及变化规律。研究结果表明:油桃的含水量与信号强度呈显著正相关,拟合方程为:y=12.415x-596.67(R2=0.9822);MRI图像可以清晰反映油桃的果肉、核壳、核仁儿等结构及其水分分布情况;新鲜油桃中含有三种状态的水,分别是结合水、不易流动水和自由水,其中自由水约为90%,结合水约为1%,剩下的为不易流动水;干燥处理能够降低水分的自由度,T2值减小,且鼓风干燥的T2减小速度比真空干燥的快;鼓风干燥过程中不易流动水向自由水迁移,自由水向外迁移散失,而真空干燥中的自由水一部分向外迁移散失,另一部分向不易流动水迁移。该研究为油桃的保藏与干燥实际产业化生产控制提供理论依据。

Analysis of Internal Moisture Changes of Nectarine during Drying Process Using LF-NMR Technology

The objective was to provide new ideas for the preservation and processing of nectarine by studying the moisture distribution and migration during drying process. The relationship between signal intensity and moisture content and moisture distribution of nectarine were determined using LF-NMR technology. The transverse relaxation time (T2) changes of nectarine with different drying methods were measured simultaneously, and then the characteristics of internal moisture state and changes were analyzed. The results showed that the water content and the signal intensity of nectarine were positively correlated and the regression equation was y = 12.415x-596.67 (R2 = 0.9822). MRI images could clearly reflect the structures of nectarine pulp, core shell and nucleolus son and the distribution of water. There were three kinds of water in fresh nectarine, bound water (about 90%), immobilized water (1%) and free water. The drying process could reduce the free degree of water with the decrease of T2, and the air drying was faster than the vacuum drying. During the air drying process, the immobilized water transferred into free water and free water lost, while a part of free water lost and the other transferred into immobilized water during the vacuum drying. This research can provide theoretical basis for the industrial production and preservation of nectarine.