Studies on the Proteolytic Action of Dairy Lactic Acid Bacteria

Part XI. The Ripening of Aseptic Rennet Curd by Streptococcus cremoris and Lactobacillus helveticus

Abstract

Aseptic rennet curd prepared under the aseptic conditions and Str. cremoris- and L. helveticus-cheese prepared by sandwiching the cell pellets of Str. cremoris and L. helveticus between aseptic rennet curd, respectively, were ripened at 10°C for desired period.
Water soluble nitrogen (WSN) contents of both aseptic rennet curd and two kinds of cheese were determined. Gradual increase of WSN content of aseptic rennet curd was recognized all through the ripening preiod. WSN contents of both Str. cremoris- and L. helveticus-cheese were remarkably higher than those of aseptic rennet curd after 12 days ripening. This tendency was more remarkably recognized after 60 or 70 days ripening. α_s-Casein was mainly hydrolyzed by these lactic acid bacteria during ripening. α_s-Casein in two kinds of the cheese was more easily degradated by these lactic acid bacteria than that in aseptic rennet curd by rennet.
Judging from the results in previous and present reports, it was estimated that lactic acid bacteria used as a starter began to autolyze after 12 days ripening and that intracellular proteases released from their cells mainly hydrolyzed α_s-casein contained in Ca-paracaseinate of aseptic rennet curd to water soluble substances. This hydrolysis was also estimated from the viscous texture observed by scanning electron micrography.