Comparison and analysis of ability to produce acid and aroma by four Streptococcus thermophilus

The changes of pH, acidity and carbonyl compounds including diacetyl and aldehyde of yogurts that were produced by four Streptococcus thermophilus in storage of 4 ℃ were compared. The study also included the correlation between these indexes, which were analyzed by sigmaplot software. The results showed that the four Streptococcus thermophilus possessed different abilities to produce acid and carbonyl compounds. Meanwhile, correlation analysis showed that diacetyl was significantly correlated with pH and acidity, but correlations between aldehyde and pH, acidity and diacetyl were not obvious.