Production of Naturally γ-Aminobutyric Acid-Enriched Cheese Using the Dairy Strains Streptococcus thermophilus 84C and Lactobacillus brevis DSM 32386

Abstract

The cheese-derived strains <i>Streptococcus thermophilus</i> 84C isolated from Nostrano cheese, and <i>Lactobacillus brevis</i> DSM 32386 isolated from Traditional Mountain Malga cheese have been previously reported as γ-aminobutyric acid (GABA)-producers <i>in vitro</i>. In the present study, the ability of these strains to produce GABA was studied in experimental raw milk cheeses, with the aim to investigate the effect of the culture and the ripening time on the GABA concentration. The cultures used consisted on <i>S. thermophilus</i> 84C alone (84C) or in combination with <i>L. brevis</i> DSM 32386 (84C-DSM). The control culture was a commercial <i>S. thermophilus</i> strain, which was tested alone (CTRL) or in combination with the <i>L. brevis</i> DSM 32386 (CTRL-DSM). The pH evolution, microbiological counts, MiSeq Illumina and UHPLC-HQOMS analysis on milk and cheese samples were performed after 2, 9, and 20 days ripening. During the whole ripening, the pH was always under 5.5 in all batches. The concentration of GABA increased during ripening, with the highest content in 84C after 9 days ripening (84 ± 37 mg/kg), in 84C-DSM and CTRL-DSM after 20 days ripening (91 ± 28 and 88 ± 24 mg/kg, respectively). The data obtained support the hypothesis that <i>S. thermophilus</i> 84C and <i>L. brevis</i> DSM 32386 could be exploited as functional cultures, improving the <i>in situ</i> bio-synthesis of GABA during cheese ripening.