Influence of fermentation and storage conditions on the sensory properties of plain low fat stirred yogurts

Influence of strain association, temperature, pH and storage on the sensory properties of low fat stirred yogurt was studied through a factorial design including three associations of thermophilic lactic acid bacteria tone Lactobacillus delbrueckii subsp. bulgaricus, one ropy and (one nonropy Streptococcus thermophilus strains), three incubation temperatures (39C, 42C and 45C), two final fermentation pH (4.4 and 4.8) and two storage times (7 and 21 days). The 36 formulated yogurts were assessed by Quantitative Descriptive Analysis and by instrumental measurements: apparent viscosity (modified funnel of Posthumus), lactate and pH. Texture perceptions and acid taste, rather than other flavor properties, gave the best discrimination between samples according to strain association, temperature and final pH. Significant two-factor interaction displayed the concomitant influence of strain association and temperature on the sample texture properties. Instrumental parameters correlated best with thickness and acid taste (pH and lactate) and mouthcoating (apparent viscosity).