PCR–DGGE fingerprints of microbial succession during a manufacture of traditional water buffalo mozzarella cheese.

Abstract

Aims:To monitor the process and the starter effectiveness recording a series of fingerprints of the microbialdiversity occurring at different steps of mozzarella cheese manufacture and to investigate the involvement of thenatural starter to the achievement of the final product.Methods and Results:Samples of raw milk, natural whey culture (NWC) used as starter, curd after ripeningand final product were collected during a mozzarella cheese manufacture. Total microbial DNA was directlyextracted from the dairy samples as well as bulk colonies collected from the plates of appropriate culture mediagenerally used for viable counts of mesophilic and thermophilic lactic acid bacteria (LAB) and used in polymerasechain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) experiments. The analysis of the DGGEprofiles showed a strong influence of the microflora of the NWC on the whole process because after the starteraddition, the profile of all the dairy samples was identical to the one shown by the NWC. Simple indexes werecalculated for the DGGE profiles to have an objective estimation of biodiversity and of technological importance ofspecific groups of organisms. LAB grown on Man Rogosa Sharp (MRS) and Rogosa agar at 30C showed highviable counts and the highest diversity in species indicating their importance in the cheese making, which had notbeen considered so far. Moreover, the NWC profiles were shown to be the most similar to the curd profilesuggesting to be effective in manufacture.Conclusions:The PCR–DGGE analysis showed that in premium quality manufacture the NWC used as starterhad a strong influence on the microflora responsible for process development.Significance and Impact of the Study:The molecular approach appeared to be valid as a tool to control processdevelopment, starter effectiveness and product identity as well as to rank cheese quality.