Microbial changes during the production of Sufu––a Chinese fermented soybean food

Sufu is a Chinese soybean cheese obtained by solid-state fungal fermentation of tofu followed by ripening in dressing mixture. The aim of this study was to quantify microflora changes during the sufu process, which is carried out under non-sterile conditions. From tofu to pehtze (tofu overgrown with fungus) stages, total counts of mesophilic aerobic bacteria (TMAB), bacterial endospores (spores), Bacillus cereus, lactic acid bacteria (LAB), Enterobacteriaceae and fungi increased. All of them decreased after the salting of pehtze. TMAB and spores in sufu with 8% and 11% salt content decreased to around 106 cfu/g during the ripening. B. cereus remained at around 103 cfu/g. LAB in sufu with 8% and 11% salt content decreased gradually to <102 cfu/g, but increased to 109 cfu/g in sufu with 5% salt. Enterobacteriaceae and fungi decreased to non-detectable level after 20 and 30 days of maturation.