University of Arkansas, Fayetteville Division of Agriculture


Soybean, natto production


Seed hardness is an important factor in determining soybean suitability for natto production. There is no established methodology for testing seed texture of soybeans. The objective of this study was to develop an efficient method by examining different instruments and seed parameters that could be potentially used for testing soybean seed hardness. Five food-grade soybean genotypes with different seed sizes were used to determine seed hardness and water-absorption capacity. Water absorption capacity was expressed by swell ratios for seed weight, seed dimension, and volume of water changes before and after soaking. Seed hardness test was conducted by a one-bite method using two food-texture analyzers: a TMS-2000 equipped with shear cell (SC) and a TA-XT2i equipped with either a single blade (SB), a 2-mm probe (PB), a 75-mm cylinder (CY), or a 16-probe pea rigs (PR). The results showed that hardness testing by CY with ten seeds (CV=0.14), SB with 5 seeds (CV=0.11), and SC with 30 g steamed seeds (CV=0.14) produced dependable and consistent results with low coefficient of variance. However, SC may not be practical for early plant selection in a breeding program due to a relatively large sample requirement. Seed size was negatively, whereas swell ratio by weight and volume was positively, correlated with seed hardness, and therefore, can be used as indirect selection indicators for seed hardness.