关键词: 冬瓜, 真空干燥, 水分, 低场核磁共振, 横向弛豫时间

Abstract: The objective of this work was to explore the water content, distribution and state changes of Benincasa hispida
during vacuum drying. The transverse relaxation time T2 inversion spectra of Benincasa hispida at different temperatures
during the drying process were measured and the characteristics of internal moisture state and changes were analyzed using
low-field nuclear magnetic resonance (LF-NMR). The results showed that the linear relationship between total NMR signal
amplitude and moisture content on a dry base during drying was established. The transverse relaxation time T2 was changed
and moisture mobility was reduced during the drying process. The moisture with high degree of freedom moved to the
moisture with low degree of freedom. The kinetic models describing the percentages of bound and free water versus drying
time followed an exponential function and a polynomial function, respectively, at different drying temperatures. The high
regression coefficients (R2 > 0.95) indicated high fitting precision of the equations. This research can provide a theoretical
basis for industrial production and preservation of Benincasa hispida.

Key words: Benincasa hispida, vacuum drying, moisture, low-field nuclear magnetic resonance (LF-NMR), transverse relaxation time T2