Rapid differentiation and in situ detection of 16 sourdough Lactobacillus species by multiplex PCR

A two-step multiplex PCR-based method was designed for the rapid detection of 16 species of lactobacilli known to be commonly present in sourdough. The first step of multiplex PCR was developed with a mixture of group-specific primers, while the second step included three multiplex PCR assays with a mixture of species-specific primers. Primers were derived from sequences that specify the 16S rRNA, the 16S-23S rRNA intergenic spacer region, and part of the 23S rRNA gene. The primer pairs designed were shown to exclusively amplify the targeted rrn operon fragment of the corresponding species. Due to the reliability of simultaneously identifying Lactobacillus plantarum, Lactobacillus pentosus, and Lactobacillus paraplantarum, a previously described multiplex PCR method employing recA gene-derived primers was included in the multiplex PCR system. The combination of a newly developed, quick bacterial DNA extraction method from sourdough and this multiplex PCR assay allows the rapid in situ detection of several sourdough-associated lactobacilli, including the recently described species Lactobacillus rossii, and thus represents a very useful alternative to culture-based methodologies

Lactococcal 949 group phages recognize a carbohydrate receptor on the host cell surface

Lactococcal bacteriophages represent one of the leading causes of dairy fermentation failure and product inconsistencies. A new member of the lactococcal 949 phage group, named WRP3, was isolated from cheese whey from a Sicilian factory in 2011. The genome sequence of this phage was determined, and it constitutes the largest lactococcal phage genome currently known, at 130,008 bp. Detailed bioinformatic analysis of the genomic region encoding the presumed initiator complex and baseplate of WRP3 has aided in the functional assignment of several open reading frames (ORFs), particularly that for the receptor binding protein required for host recognition. Furthermore, we demonstrate that the 949 phages target cell wall phospho-polysaccharides as their receptors, accounting for the specificity of the interactions of these phages with their lactococcal hosts. Such information may ultimately aid in the identification of strains/strain blends that do not present the necessary saccharidic target for infection by these problematic phages

Modified Atmosphere Packaging and low temperature storage extend marketability of cherimoya (Annona cherimola Mill.)

Cherimoya is a subtropical fruit characterized by a delicious, sweet flavor and beneficial health properties, which found suitable growing conditions in the South of Italy. However, the marketing of this product is halted by its high perishability, which limits the shelf-life of the fresh fruit to few days after harvest and does not allow for commercialization beyond local markets. Studies have shown that storage of this fruit in controlled atmosphere, using Modified Atmosphere Packaging technologies, extended the post-harvest life of Cherimoya, but little is still known about the evolution of its sensory, nutraceutical and microbiological characteristics during such storage period. In this paper, we studied the effect of a 4-days long active-MAP (30% CO2 – 10% O2 – 60% N2) storage period, associated with cold temperatures, on the physico-chemical, sensory, nutraceutical and microbiological quality traits of Italian-grown cherimoya fruits, compared with passive-MAP (Air composition, 21% O2 + 1% CO2 + 78% N2) and simple cold storage. Active-MAP proved effective in delaying the reaching of the optimal consumption point until 10 days from harvest, besides showing absence of microbial growth until after 7 days from harvest. Both active- and passive-MAP treatments maintained better nutraceutical values than control until the end of the trial period, and sensory analysis confirmed that active-MAP treated fruits were at the optimal commercial stage after 10 days from harvest

Microbial Safety of Black Summer Truffle Collected from Sicily and Umbria Regions, Italy

Background: Tuber aestivum Vittad., known as black summer truffle, represents high-value food especially used as garnishment in nouvelle cuisine. The aim of this study was to investigate on the viable microbial populations associated with T. aestivum ascomata collected in different sites of Sicily and one locality of Umbria (Italy). Methods: The ripe ascomata of black summer truffles were collected from Central Italy. Cell densities of spoilage bacteria, fecal indicators, potential pathogens, yeasts, and molds were analyzed. Statistical analysis was conducted with XLSTAT software. Results: The microbiological counts of truffles ranged between 6.00 and 9.63 log Colony Forming Unit (CFU)/g for total mesophilic count and between 6.18 and 8.55 log CFU/g for total psychrotrophic count; pseudomonads were in the range 6.98-9.28 log CFU/g. Listeria spp. and coagulase-positive streptococci detected in no samples. Coagulasenegative streptococci were found in some samples with 2.11-4.76 log CFU/g levels. Yeasts and filamentous fungi were detected at consistent levels of 3.60-7.81 log CFU/g. Significant differences (p<0.01) were found between samples and also for all microbial groups. Conclusion: This study evidenced that the common brushing procedure applied for preparation of truffles is not sufficient to eliminate microbial risks for consumers. The application of an efficient decontamination treatment is strongly suggested before consumption of fresh truffles