FORMATION OF AMINO-ACID (L-LEUCINE, L-PHENYLALANINE) DERIVED VOLATILEFLAVOR COMPOUNDS BY MORAXELLA-PHENYLPYRUVICA AND STAPHYLOCOCCUS-XYLOSUS IN CURED MEAT MODEL SYSTEMS

A bacterial strain isolated from Danish immersion curing brine, Moraxe lla phenylpyruvica 0100, and a commercial meat starter culture, Staphy lococcus xylosus DD34, were tested for their ability to form character istic volatile compounds in minimal medium with the added amino acid L -leucine or L-phenylalanine under different environmental conditions ( pH 5.5 and 6.0; 0 and 210 ppm nitrate; pre-incubation with and without agitation) and compared with respect to their ability to form volatil e compounds in cured meat extracts and vacuum-packed cured meat cuts. The characteristic cured meat aroma precursors/compounds 3-methylbutan al and 3-methylbutanol were found to be formed in cured meat extracts and vacuum-packed cured meat cuts inoculated with M. phenylpyruvica. T hese volatiles are most probably formed by metabolic conversion of the amino acid L-leucine by M. phenylpyruvica, as they were also produced in minimal media with added L-leucine inoculated with this organism. The characteristic L-phenylalanine derived compound, benzaldehyde, for med by M. phenylpyruvica in minimal medium in the presence of nitrate (210 ppm), was not produced in any noticeable amount in cured meat ext racts or vacuum-packed cured meat inoculated with M. phenylpyruvica. I n contrast, benzacetaldehyde, which has been described as a possible m etabolic product of the microbial conversion of L-phenylalanine, was f ound to be a characteristic volatile compound formed in cured meat ext racts and vacuum-packed cured meat inoculated with M. phenylpyruvica, indicating an alternative metabolic pathway for L-phenylalanine by thi s organism in a cured meat environment. Even though S. xylosus was abl e to form volatile compounds characteristic of cured meats (3-methylbu tanal, 3-methylbutanol) in minimal media with added L-leucine, this ba cterial strain seemed not to be able to produce these characteristic v olatiles in the studied cured meat systems. The present data imply tha t M. phenylpyruvica, in particular, is a potential meat starter for en suring superior flavour development in cured meat. (C) 1998 Elsevier S cience B.V.