ISOLATION AND IDENTIFICATION OF LACTIC ACID BACTERIA PRESENT IN BEAN (Phaseolus vulgaris L.) FLOURS

G. D. SÁEZ; E. M. HEBERT; L. SAAVEDRA; A. PÉREZ CHAIA; G. ZÁRATE

San Miguel de Tucumán

Simposio; International Symposium on Lactic Acid Bacteria; 2016

CERELA_CONICET

Beans production (Phaseolus vulgaris L.) is one of the most important regional economies inthe Northwest of Argentina, mainly in the provinces of Salta and Tucumán. Flours obtainedfrom these legumes possess an interesting nutritional value which turns them into an optionfor healthy diets. However, these flours should be subjected to industrial processing in orderto improve their technological properties and obtain products with higher rheological andorganoleptic quality. In this sense, the fermentation with Lactic Acid Bacteria (LAB) is an alternativeto enhance flours quality due to the synthesis of metabolites that positively impact inthe final product. Therefore, the aim of this work was to isolate and characterize LAB strainsfrom different varieties of P. vulgaris flours to be used in the future for the fermentation ofthese matrices. Samples of different varieties of beans (Alubia, Pallar, red and black beans)were ground individually, mixed 1:1 with sterile distilled water and incubated aerobically at37°C for up to 5 days with daily backslopping (10% sourdough + 90% fresh dough). Samplestaken at 0, 1, 3 and 5 days were inoculated in selective media for BAL: MRS with cycloheximide0.1 % and LBS and were also plated in PCA and HyL media to estimate the cultivablemicrobiota (total aerobic mesophiles and fungi/yeasts, respectively). Evolution of pH was followedduring fermentation. Colonies grown in MRS and LBS with presumptive characteristicsof LAB (Gram + and catalase -) were selected and differentiated by REP-PCR. The isolates withdifferent profiles were identified by the amplification of the V1 variable region of 16S rRNA.Initial mesophiles counts of 4.13x104, 1.84x104, 4.55x103, and 3.46x104 CFU/g for Alubia, Pallar,red and black varieties, respectively, reached values around 109 CFU/g after 5 days offermentation for all the doughs, whereas the counts of fungi and yeasts started at 2.22x103,1.37x103, 5x102 and 3x103 CFU/g for each type of flour, remained around 104 CFU/g duringsuccessive days and finally decreased by 1-2 logarithmic orders at the end of fermentations.Lactic microbiota began to dominate after 24 h of fermentations with values of 2.57x108 inAlubia, 6.78x107 in Pallar, 1.20x107 in red and 2.26x108 CFU/g in black beans, and reachedfinal values of 6.74x108, 5.35x108, 1.71x108 and 2.65x108 CFU/g, respectively. The pH of alldoughs decreased from 6.6-6.2 to 4.3-3.9 at the end of fermentations. LAB strains were identifiedas Enterococcus caseliflavus (2), E. durans (4), E. faecium (5) E. mundtii (1), Lactobacillusrhamnosus (1), Lactococcus garvieae (3), Weissella cibaria (4), and W. paramesenteroides (5).These results represent the first step in the selection of suitable starters for legume floursfermentation.