热风干燥过程中带壳鲜花生水分迁移特性及品质变化

Moisture Migration Properties and Quality Changes of Fresh In-Shell Peanuts during Hot Air Drying

为提高带壳鲜花生在热风干燥过程中的品质,本实验以带壳鲜花生为原料,研究热风干燥(40、50、60℃)过程中带壳鲜花生的水分迁移特性及品质变化。结果表明:在热风干燥过程中,带壳鲜花生的水分含量变化明显,弱结合水含量逐渐减少。随着干燥的进行,花生仁与花生壳的网状结构变形,孔隙率增大,且温度越高,孔隙率越大。带壳鲜花生干燥过程为降速干燥,当干燥温度从40℃提升至60℃,干燥至花生安全水分含量以内所需时间缩短45%,表明温度升高有利于加快脱水速率。此外,受水分含量的影响,花生仁硬度在较高温度下呈先增大后减小再增大的趋势,在较低温度下则持续增大,而花生壳硬度先减小后增大。通过相关性分析发现,干基水分含量与低场核磁共振信号幅值呈极显著正相关(P<0.01),与花生仁孔隙率和花生壳孔隙率呈极显著负相关(P<0.01),与花生仁硬度呈显著负相关(P<0.05)。本实验为带壳鲜花生热风干燥过程的水分实时监测及实现高品质干燥提供了理论依据。

In order to improve the quality of fresh in-shell peanut during hot air drying process, water migration characteristics and quality changes during hot air drying at different temperatures(40, 50 and 60 ℃) were investigated in the present study. The results showed that during the hot air drying process, the moisture content of fresh in-shell peanut changed significantly, and the content of weakly bound water decreased gradually. As the drying process progressed, the network structure of both peanut kernels and shells was deformed, and the porosity increased, which increased with increasing drying temperature. The drying process took place in the falling rate period. The drying time required to reach a moisture content within the safe limit was reduced by 45% when the drying temperature increased from 40 to 60 ℃, indicating that increasing temperature is helpful to accelerate the dehydration rate. In addition, under the influence of water content, the hardness of peanut kernels first increased, then decreased and finally increased once again at higher drying temperatures, and continuously increased at lower drying temperatures, while the hardness of peanut shells first decreased and then increased. According to the correlation analysis, the dry-basis moisture content was significantly positively correlated with the amplitude of low-field nuclear magnetic resonance signal(P < 0.01), negatively correlated with the porosity of peanut kernels and shells(P < 0.01) as well as the hardness of peanut kernels(P < 0.05). This paper provides a theoretical basis for the real-time monitoring of moisture during the hot air drying process of fresh in-shell peanuts and for high-quality drying.