Figure 10.1. Meat starter culture bacteria: major metabolic pathways in meat fermentation . Main
enzymatic activities of coagulase negative staphylococci and lactobacilli are indicated by light grey arrows and
dark grey arrows, respectively. The metabolic activities ascribed to both bacterial groups are indicated by white
arrows. Dotted - line arrows indicate action of endogenous meat enzymes. Abbrevations: a.a., amino acids; Arg,
arginine; B.A., Biogenic Amines; Orn, ornithine. Sugars added to the batter are rapidly metabolized to lactate
by starter cultures of lactic acid bacteria. Glycogen, proteins, and lipids catabolism are also used for microbial
growth during fermentation. Ribose is released by ATP hydrolysis, and the subsequent metabolism of ribose -
derived molecules is used for energy production by L. sakei . When sugar concentration declines, free amino
acids (a.a) are utilized for microbial growth. Via the arginine deiminase (ADI) pathway, arginine is converted to
ornithine and supports the growth of lactobacilli in the latter stage of meat fermentation. Staphylococci modulate
the aroma through the conversion of amino acids (particularly the branched - chain amino acids leucine,
isoleucine, and valine) into methyl - branched aldehyde, methyl - branched acids and sulphites, diacetyl, and ethyl
ester. The methyl ketones (2 -pentanone and 2 - heptanone) derive from intermediates of an incomplete ß -
oxidation pathway in staphylococci.