Aerobic heterotrophic microbial populations isolated from cooked vegetables

A "shelf-life" study was performed using a combination of PCR-based techniques to investigate the dynamics of microbial populations isolated from a "range V" product (a cooked vegetable, chard) during the normal storage time. Bacterial isolates were collected on different sampling days and grouped into 7 different haplotypes, identified by Amplified Ribosomal DNA Restriction Analysis (ARDRA), suggesting a low genetic diversity of the bacterial community. The taxonomic positions of the isolates belonging to the four main haplotypes were determined by 16S rDNA sequencing. The main genus was Pseudomonas, whose main ARDRA group was analysed by the RAPD technique, which identified 8 genotypes showing a very low degree of biodiversity also at the intraspecific level. The main contamination of the product was probably derived from an initial contamination of the vegetables. Modifications introduced into the production procedure resulted in a marked reduction of the microbial titre.