Changes in the physicochemical composition of Auricularia auricula during growth stages and control of endogenous formaldehyde

To maintain quality and reduce endogenous formaldehyde content in the edible fungus, Auricularia auricula, the critical period of formaldehyde generation was identified and controlled. In this study, different growth stages of A. auricula were used to assess the nutritional composition (polyphenol monomers, 5'-nucleotides, organic acids and water-soluble vitamins) and related enzyme activities; the correlation between quality and endogenous formaldehyde content was also analysed. The results showed that formaldehyde was positively correlated with soluble protein and melanin levels; it was negatively correlated with the total sugar and flavonoid contents. Among the four growth stages, ripe A. auricula (RAA) had the highest endogenous formaldehyde content. The activities of gamma-glutamyl transpeptidase (GGT) and L-cysteine sulphoxide lyase (C-S lyase) were highest in RAA; they promoted endogenous formaldehyde production. RAA is a critical period for interventions to reduce endogenous formaldehyde contents. Experiments to distinguish the effects of 10 exogenous substances on GGT and C-S lyase indicated that cysteine (Cys) and glutamic acid (Glu) inhibited the production of endogenous formaldehyde by 17.13% and 14.89%, respectively. This study provides a new perspective for controlling safety during the growth of edible fungi and maintaining the quality of processed products.

Automated summary

This study identified the critical period for generating endogenous formaldehyde in Auricularia auricula and found that ripe A. auricula had the highest endogenous formaldehyde content. The activities of gamma-glutamyl transpeptidase and L-cysteine sulphoxide lyase promoted the production of endogenous formaldehyde. Experiments showed that cysteine and glutamic acid inhibited the production of endogenous formaldehyde. This study provides new insights for controlling safety and maintaining quality in the growth of edible fungi.