Analysis of key fungi and their effect on the edible quality of HongJun tofu, a Chinese fermented okara food

Abstract

HongJun Tofu is produced by fungal (named “HongJun”) fermentation of okara, which is a major byproduct of the soymilk and tofu industry. The dynamic characteristics of the fungal community (predominantly “HongJun”) might have significant influences on HongJun Tofu during a short period, however, this remains unclear. In the present study, the “HongJun” was identified, and the edible quality of HongJun Tofu including nutritional composition, physical properties, and sensory level was evaluated. Further, the correlation between fungal diversity and edible quality during fermentation was analyzed. The results showed that “HongJun” is a novel strain (named OM009248) of Neurospora crassa. In the pre-fermentation (0–24 h), Neurospora crassa multiplied rapidly and reached the maximum abundance, while in the pro-fermentation (24–48 h), other fungi including Trichosporon and Rhizopus occupied certain content. The correlation analysis showed that Neurospora crassa was positively correlated with increased nutrients including oligopeptides, free amino acids (FAAs), β-carotene, and soluble dietary fiber (SDF) as well as enhanced texture, including springiness and chewiness; Trichosporon was negatively correlated with fat and Rhizopus was positively correlated with SDF. These findings provide a theoretical reference for quality control of HongJun Tofu commercial production.