Influence of fermentation and storage conditions on the sensory propertiesof 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 desig n including three associations of thermophilic lactic acid bacteria tone La ctobacillus delbrueckii subsp. bulgaricus, one ropy and (one nonropy Strept ococcus 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 Descripti ve Analysis and by instrumental measurements: apparent viscosity (modified funnel of Posthumus), lactate and pH. Texture perceptions and acid taste, r ather than other flavor properties, gave the best discrimination between sa mples according to strain association, temperature and final pH. Significan t two-factor interaction displayed the concomitant influence of strain asso ciation and temperature on the sample texture properties. Instrumental para meters correlated best with thickness and acid taste (pH and lactate) and m outhcoating (apparent viscosity).