Measurement of the Water Content and the Moisture Vaporization Enthalpy in Rice Cracker with Portable Near Infrared Spectrometer

The water content of rice cracker was measured by a milled and dry-weight method, and was predicted by a linear regression analysis at a peak around the 1917 rim by a near infrared (NIR) spectrum using a portable NIR spectrometer after a spectra-pre-treatment. The correlation between the value by the dry weight method and the NIR predicted value was r(2) = 0.946. Therefore, predicting the water content of rice cracker was possible using a portable NIR spectrometer. The water content could be measured even from the outside of a plastic bag. By an analogy of a Clausius-Clapeyron equation, partial derivative(lnw)/partial derivative(1/T/K) = Delta H/R (w; water content, Delta H; vaporization enthalpy change) is obtained. The water content of four kinds of rice cracker at 20-135 degrees C was measured and Delta H for the rice crackers were obtained from the slope of plots of (ln [w/mol/kg]) vs. (1/T/K). The result shows that one can discuss the hydroscopic difference between rice crackers from the Delta H.