353. ‘Malty’ flavour in starter and butter

Abstract

A Gram-positive, aroma bacterium, the so-called ‘malt coccus’, has been isolated from malty-flavoured starters. It coagulates milk most readily at 35–37° C. The ‘malt coccus’ differs from the aroma bacteria mainly in that it forms acetaldehyde from pyruvic acid, evidently through carboxylase. Acetaldehyde is the chief factor in the formation of malty flavour. The ‘malt coccus’ sours milk feebly. If starter is heavily contaminated with the ‘malt coccus’, the acidity (SH°) is reduced but the aroma reaction (V.-P.) increases. The malty flavour persists in the starter during transfers and becomes more marked with rising temperature. The ‘malt coccus’ retains its aroma-forming ability for long periods in the laboratory.