In this study, sufu samples were prepared essentially
according to the procedure described by Li et al. (3). Briefly, tofu cubes were first
combined with salt and water. After being held at room temperature for 24 h, the salted
tofu cubes were then air-dried for 24 h. Meanwhile, A. oryzae was grown in a mixture of
steamed rice and soybean and held at 35°C and 70% relative humidity for 40 h, resulting
in the rice-soybean koji (3). The rice-soybean koji mash was further prepared by
mixing the prepared koji with syrup (65% sucrose) at room temperature for 48 h. The
sufu was then ripened by mixing the salted tofu cubes with koji mash in a glass jar
which was held at 37°C for a period of 16 days (16-day sufu). Additionally, the 46-day
sufu was also obtained by holding the sufu-containing jar at room temperature
(approximately 25°C) for another 30 days. This is the general practice employed in
some factories before sufu products are distributed for sale in the market.