Analyzing Soybean Seeds Using Near-Infrared Spectroscopy for Simplifying the Estimation of Tofu Firmness

Abstract

Differences in the processing quality of tofu, particularly firmness (defined as breaking stress), were estimated by analyzing soybean seeds using near-infrared spectroscopy (NIRS). All NIRS measurements on soybeans grown in different years, in different sample forms (whole or pulverized seed), and types of spectra (raw or second derivative), showed a strong correlation with the measured firmness of the resulting tofu. Estimates of firmness calculated from the second derivative spectra of whole soybean seeds provided the easiest scanning process, which was most suitable for unknown samples. Because the prediction accuracy was also good for soybean seeds grown in different years, this NIRS method is not only accurate enough for practical use in screening but also has the potential for evaluating and selecting breeding lines of soybean, especially in early generations.