Green alternative for sodium metabisulfite substitution: Comparison of bacterial and fungal proteases effect in hard biscuit making.

Sodium metabisulfite is one of the most employed reducing agents in hard biscuit making. The recent results about its adverse effects on human health have pushed us to look in new safer and greener directions. Two different proteases, from distinct strains (bacterial and fungal), were selected and their effects on the dough thermomechanical performances, texture, and structure of the hard biscuits were compared with those obtained from the sodium metabisulfite. Doughs treated with fungal protease showed higher stability during mixing and higher consistency throughout the heating stage. On the other hand, bacterial protease had the greatest weakening effect on protein with a marked reduction of starch gelatinization. Doughs processed with fungal enzymes reached similar values to those containing sodium metabisulfite. In terms of hardness, no significant (p < 0.05) differences were found between biscuits made with bacterial protease and sodium metabisulfite. Analysis of the volumetric characteristics highlighted that bacterial enzymes gave higher values of specific volume and surface area. Regarding the structure of the hard biscuits, sodium metabisulfite produced a more uniform structure with fewer and smaller pockets as compared with the samples treated with proteases.