Avaliação do efeito da adição de culturas lácteas bioconservantes nas características físico-químicas, microbiológicas, reológicas e de textura do iogurte.

Abstract

This study investigated the effect of commercial bio-preservatives FRESHQ-11 (Lactobacillus rhamnosus) and HOLDBAC-YMB (L. rhamnosus and P. freudenreichii subsp. shermanii) at different dosages on the fermentation kinetics, pH, titratable acidity (%), fungal inhibition and textural parameters (firmness, consistency, cohesiveness and viscosity index) of yogurt during 28 days of storage at 7±1 °C, with references being yogurt formulated only with the chemical preservative potassium sorbate at the maximum permitted concentration (control1) and yogurt without chemical preservative (control2), as an alternative to replace or reduce the concentration of potassium sorbate in preserving this product. For this purpose, yogurts were formulated with two types of commercial bio-preservatives at dosages of 0.1% and 0.2% (v/v), and potassium sorbate concentrations of 0.015g/100g and 0.03g/100g. In general, the two commercial biopreservatives reduced the fermentation time in relation to the control1 yogurt (with 0.03g/100g potassium sorbate) and mainly in relation to the control2 yogurt Yogurts with bio-preservatives exhibited a lower pH and significantly higher titratable acidity (%) than yogurt control2 (p < 0.05). The syneresis of all experiments decreased significantly over the storage period (p < 0.05) during the 28 days at 7±1°C. In experiments containing bio-protective cultures, the yogurt texture parameters were significantly lower (p < 0.05) than in control1 and control2 yogurts during the storage period. In phase I, the experiments containing bioprotective cultures had a similar performance to the yogurt control1 in preventing molds and yeasts, especially when the commercial culture FRESHQ-11 (L. rhamnosus) was used at a dosage of 0.2%v/v (F3 yogurt). The initial contamination of the yogurt with a concentration of molds and yeasts of 1.2x101 CFU/g altered the pH behavior during the studied period, considering that in phase II, the pH at 28 days of expiration was lower for all yogurts studied. In the case of titratable acidity (%), in phase II, a slight decrease was observed in control1 and H3 yogurts and a considerable increase in control2 and F3 yogurts. The initial contamination with molds and fermented yeasts at a concentration of 1.2 x 101 CFU/g of yogurt contributed to the increase in syneresis of control1 and H3 yogurts and had practically no effect on F3 yogurt in relation to phase I. However, control2 yogurt had a strong decrease in syneresis and presented much higher values for the texture intervals in phase II. The initial contamination of the yogurt with 1.2 x 101 CFU/g of molds and yeasts did not significantly influence the performance of these sessions in control1, H3 and F3 yogurts. In general, it can be stated that the yogurt experiments containing the biopreservatives HOLDBAC-YMB and FRESHQ-11 performed very well in inhibiting molds and yeasts, even with an initial contamination of 1.2 x 101 CFU/mL, mainly in H3 yogurt when the commercial biopreservative HOLDBAC-YMB was used at a dosage of 0.2%v/v.