Preliminary performance of heterofermentative lactobacilli in non-dairy matrixes: silage and dough

BRAIDA, JESICA; PEVERENGO, MARÍA ROCÍO; PUJATO, SILVINA ; QUIBERONI, ANDREA; CAPRA, MARÍA LUJÁN

San Miguel de Tucumán

Simposio; V International Symposium on Lactic Acid Bacteria; 2016

CERELA-CONICET

Obligated heterofermentative lactobacilli (OHeL) produce CO2 from hexoses and may be present in raw rnilk as non-starter lactic acid bacteria (NSLAB). As alllactic acid bacteria possess GRAS status (Generally Recognized As Safe). Their presence in silage and in sourdough has also been reported. The aims of this study were to characterized 16 dairy autochthonous OHeL strains (12 Loctobocillus fermentum, 2 Loctobocillus brevis, 1 Loctobocillus buchneri y 1 Weissello ciborio) and assess their performance in non-dairy matrixes. Inoculum (2%, v/v) and optimal temperature, Topt (37"C, L. fermentum and 30°C, the rest of the species) were determined by microplates assays. In spite of their isolation from dairy samples, all strains displayed scarce growth in milk. The acidification activities (potentiometric titration NaOH N/9 pH 8.4) were low and proteolytic activities (OPA test) almost null, when strains were developed at their Topt (24 h, reconstituted sterile rnilk 10% w/v with or without extract yeast 0.25% w/v). The growth on liquid corn extract medium of L. brevis and L. buchneri was evaluated by cell counts, pH determination and organic acid quantification (Iactic and acetic acids, HPLC, 72 h). The strains were able to grow reaching the highest increments (0.9-1.2 log lO orders) between 24 and 72h. The pH values descended up to 4.4-5.0 in the cultures and the concentration of lactic (0.89±0.01 - 1.18±0.09 mg/mL) and acetic acid (0.24±0.02 - 0.31±0.01 mg/mL) was showed promissory for use in silage. All (16) strains were tested for exopolysaccharides (EPS) production. EPS can improve texture and prolong shelf life of bread. Screening was made by visual detection of mucoid colonies grown in agar media (MRS and MRS maltose-sucrose 1-10%w/v MRS-MS; 2-4 d, 30°C). L.fermentum (strains 22 and 68), L. brevis (strains 61 and 66), W ciborio (strain 20) y L. buchneri (strain 39) were selected and the better results were found in MRS-MS. Growth of W ciborio 20 in wheat flour and in a celiaccommercial mix was assessed (cell counts, total titratable acidity and pH determination). In both controls (without W ciborio), the spoilage bacterial counts (initially 103-104 UFC/g) was notably increased (4.7-4.9 10glOorders) after 24 h of incubation (30°C). On the contrary, this spoilage flora was completely inhibited when W ciborio 20 was inoculated (5xl07 UFC/g). The strain was able of growing in both kinds of dough and showed cell count increases (0.7-0.9 10glOorders) after 24 h. The strain produced more acidity and higher descent on pH values in comparison with its respective controls without inoculums. The abilitv to grow on corn extract medium as well as in both types of dough, sets the studied strains as interesting candidates to be starter cultures for fermentations in non-dairy matrixes.