Microbiology and biochemistry of traditional mozzarella cheese

Seven mozzarella cheeses from the Apulia region were analysed for compositional, microbiological and biochemical characteristics. Mean values for the gross composition of the seven cheeses differed significantly. Moisture was high in most samples, salt levels varied considerably from 1.6% to 0.5%. The pH was high in all samples (6.29-5.82), except for one sample (5.41) that showed the highest content of lactic acid bacteria. One hundred and forty-one isolates were analysed by RAPD-PCR and identified by partial sequencing of 16S rRNA gene. Twelve species were identified. Lactobacillus helveticus was found in all starter samples. Lactobacillus fermentum, Lactobacillus plantarum, Lactococcus lactis, Lactococcus garviae and Streptococcus thermophilus were dominant. RADP analyses showed biodiversity among the strains. Analysis of pH 4.6-insoluble fractions by urea-PAGE showed hydrolyses of β-CN to γ-CN suggesting plasmin activity. Some cheeses showed less β-CN breakdown and more α_s1-CN degradation. RP-HPLC performed on pH 4.6-soluble, ethanol 70%-soluble and insoluble fractions showed various differences in peptide profiles of cheese samples.