Flavour compounds produced by Lactobacillus paracasei I90 in a hard cheese model

PERALTA GUILLERMO; WOLF I.VERÓNICA; BERGAMINI CARINA V.; ABEIJÓN MUKDSI M. CLAUDIA; PEROTTI M.CRISTINA

Egmond aan Zee. The Netherlands.

Simposio; 10th Symposium on Lactic Acid Bacteria; 2011

Abstract Adjunct cultures of mesophilic lactobacilli may be added into cheese to improve control over microbiota and quality. Selected strains are also expected to intensify or diversify cheese flavour during ripening by increasing secondary proteolysis and aminoacids metabolism. For flavour production via aminoacids metabolism, aminotransferases (ATs) are key enzymes. In this work we assessed the ATs profile of Lactobacillus paracasei I90, selected for its ability to increase secondary proteolysis in cheese and its technological performance as a secondary culture. We also tested the impact of L. paracasei I90 on the production of flavour compounds derived from aminoacids in a hard cheese model. AT activities were determined on branched (Leu, Val, Ile), and aromatic (Thr, Trp, Phe) aminoacids as well as aspartic acid and metionine, by quantifying glutamic acid derived from transamination reaction. Lb. paracasei showed AT activity towards all aminoacids. However, the higher levels were observed for Asp, followed by branched-chain aminoacids and Trp. Cheese model consisted of a sterile extract representative of the aqueous phase of cheese. Extracts were inoculated with Lb. paracasei and incubated at 34ºC for 14 days. Non-inoculated controls were also prepared. The volatile compound analysis was performed by solid phase microextraction (SPME) and GC-FID/MS. Car/PDMS fiber was selected from four fibers tested, as it showed better extraction efficiency. Among the volatile compounds derived from aminoacids, 2-methyl butanal, 3-methyl butanal, benzaldehyde, diacetyl, phenol, DMDS, methional and 3-methyl butanol, were detected at higher level in extracts inoculated with Lb. paracasei than in controls. We concluded that Lb. paracasei I90 has key aminotransferases activities on Asp, Trp, and branched-chain aminoacids and increased the production of flavour compounds derived from them in a hard cheese model.