Native lactic acid bacteria and evolution of sugar and organic acids contents during ripening of semihard goat cheeses

H NEME; R MEDINA; N TABOADA; S LOPEZ ALZOGARAY

San Miguel de Tucumám

Simposio; Native lactic acid bacteria and evolution of sugar and organic acids contents during ripening of semihard goat cheeses; 2016

CERELA-CONICET

The aim of this work was to obtain the profile of the formate, acetate, propionate, lactate, citrate, lactose, ethanol and diacetyl-acetoin, present in the matrix of experimental cheeses at 0, 45 and 60 days of ripening, by using HPLC. Three different cultures were used in semihard goat cheese making: S (native starter culture constituted by Lactobacillus (L.) rhamnosus, L. delbrueckii subsp. bulgaricus, Streptococcus (S.) thermophilus), A (culture S plus adjunct culture constituted by native L. plantarum and Pediococcus pentosaceus), C (commercial culture constituted by S. thermophilus). Three types of semihard goat cheese were made (CS, CA and CC) with pasteurized milk, by adding an inoculum at 2% (v/v) of each culture S, A or C. Metabolites content was expressed as g/kg of cheese. Formate was detected in CA and CC at 0 (0.10) and 45 days (0.34). At T0, levels of acetic acid in CS (0.75) and CA (0.63) were higher than those in CC (0.42); in CS and CA, levels were decreasing over time, were null at T60 in CC. In CC, ethanol was not found; in CS and CA, the starting values were tripled at 45 days (CS, 0.95; CA, 0.70) and then returned to baseline values. Propionic acid was only detected in CS and CA (0.91 and 0.86, respectively) at T0, but CC presented values at 45 (0.29) and 60 (0.16) days. The largest increases in lactic acid content were found in CS (11.83) and CA (10.71); in CC, the final value tripled to start.At 45 days, the initial values of citric acid decreased 4 times in CS and CA and 10 times in CC; at 60 days, citric acid was not detected. From 45 days, the initial lactose was completely metabolized. No galactose was detected in any case, this is desirable because the accumulation of galactose promotes browning caused by the Maillard reaction. At T0, diacetyl-acetoin was present in all samples; at T45, only in CA; at T60 was absent in all samples, possibly due to the decrease in the concentration of citrate. Cheeses made with native strains (CS and CA) showed a significant reduction in lactose and a significant increase in lactic acid, acetic acid and ethanol content. The excellent texture was related to the pH values reached in the cheese matrix. The specific role of ethanol in the flavor of the cheese is limited, but it is the precursor of relevant compounds in the aroma, such as ethyl esters. The results suggest that native lactic acid bacteria grew conveniently in the cheese matrix, developing their full potential as reflected in the profile of the metabolites released during ripening.