Whey Starter for Grana Padano Cheese: Effect of Technological Parameters on Viability and Composition of the Microbial Community

Comparison of natural whey starters from different Grana Padano cheese dairies. The x-axis represents the whey samples (A to L). Panel A) Length heterogeneity-reverse transcription-PCR results: the y-axis represents the percentages of the relative peak areas corresponding to Lactobacillus helveticus (gray), Lactobacillus delbrueckii ssp. lactis (white), Streptococcus thermophilus (dark gray), and Lactobacillus fermentum (black). Panel B) Fluorescence microscopy counts: the y-axis represents the percentages of viable (white) and nonviable (dark gray) populations.

Comparison of whey starter treatments. The y-axis represents the relative peak area of the species from fresh whey starters (dark gray) and whey starters subjected to different thermal stresses: 24h at 4°C (white), 24h at −20°C (gray), and 1h at 54°C (black). Error bars indicate standard deviation from 3 (4°C) or 2 (−20 and 54°C) experiments.

Length heterogeneity-reverse transcription-PCR electropherograms showing the profile obtained by analyzing the lactic acid bacteria population of Grana Padano whey starters traditionally prepared and enriched with 3 different concentrations (0.3, 0.5, and 1%, wt/vol) of yeast extract as a microbial growth-stimulator factor: Streptococcus thermophilus (1), Lactobacillus delbrueckii ssp. lactis (2), Lactobacillus helveticus (3). The pie chart represents the percentages of total viable (gray) and nonviable (white) populations.