BIOGENERATION OF FLAVOUR COMPOUNDS BY L paracasei I90 AND L. helveticus B02 IN A HARD CHEESE MODEL

CUFFIA F.; WOLF I. V.; HYNES, E.R.; BERGAMINI, C.; PEROTTI M.C.

Simposio; Simposio de bacterias lácticas; 2013

Amino acid (AA) catabolism by lactic acid bacteria is one of the most important biochemical events that lead to bioformation of cheese flavour. The selection of adjunct strains of mesophiliclactobacilli possessing key enzymatic activities to AA catabolism and its combination withappropriate primary cultures represents an interesting strategy to accelerate or diversify the flavordevelopment in cheeses. The aim of the present work was to evaluate the ability to producevolatile compounds derived from AA in a hard cheese model by a strain of mesophilic lactobacilli,Lb. paracasei I90, and a strain of thermophilic starter, L. helveticus B02, which were addedindividually and mixed. Hard cheese model consisted in a sterile extract standardized in salt contentand pH, obtained from the aqueous phase of a Reggianito cheese manufactured with L. helveticusB02 and ripened for 3 months. From this model system were prepared: extracts inoculated with thesame strain of L. helveticus (re‐inoculation) used in cheese‐making, extracts inoculated with L.paracasei I90, extracts inoculated with both strains, and control extracts with not addedlactobacilli. They were incubated at 37ºC for 14 days. The assays were performed in duplicate, byusing two independent cultures of each strain for the inoculation. The production of volatilecompounds was monitored by solid‐phase microextraction (SPME) coupled to GC‐FID and GC‐MS. Atotal of 38 volatile compounds were identified in the cromatographic profiles of extracts. However,only 13 were related to AA catabolism: acetaldehyde, 2‐ and 3‐methyl butanal, ethanol, diacetyl,acetoin, 3‐methyl 1‐butanol, benzaldehyde, acetophenone, acetic acid, 3‐methyl butanoic acid,phenylmethanol and phenol. The levels of acetaldehyde were statistically higher in the extractsinoculated with both strains in comparison to the rest of the extracts. Diacetyl, 3‐methyl 1‐butanoland acetic acid had higher area values in all inoculated extracts in comparison to the controls. Inparticular, acetic acid was produced in higher levels in the extracts containing the mixed strainsthan in those with individual strains. A preferential production of isovaleric acid was observed inthe extracts with L. paracasei I90 both alone as combined with L. helveticus B02. The cooperationeffect between both strains was only detected for acetaldehyde and acetic acid. The benzaldehydeand phenylmethanol levels were always higher in the control extracts. Both strains did notsignificantly increase the amount of the remaining volatile compounds derived from AA. In thepresent study, L. helveticus B02 and L. paracasei I90 affected the production of some volatilecompounds that play a key role in the aroma, therefore, these strains could be used in cheesemaking in order to improve flavour development.