Selezione di starter produttori di batteriocine per l'allungamento della shelf-life di prosciutto cotto affettato confezionato in atmosfera modificata

In recent years, consumers have increasly demanded healthy and safe foods, but characterized by minimal processing, with less preservatives and additives, but preserved quality and sensory characteristics. In response to these requets, in the last decade, a new approach to food stabilization has been defined; this approach called bioprotection (or bioconservation), is based on the antagonism exercised by some microorganisms towards others. Because lactic bacteria occur naturally in many food systems and are characterized by a long history of safe use in fermented foods, they have great potential to be used in the bioprotection of certain food products. Cooked ham is a product widely consumed in different countries, that belongs to heat treated meat products; heat treatment plays an important role in the selection of bacteria that can develop in the product. However, heat treatment is not always considered effective, especially with respect to the vegetative forms of thermotolerant bacteria; moreover, it has no effect towards secondary contaminations that can develop during the handling of the products after the heat treatment, and above during slicing and packaging phases. For this reason, preservation and distribution at refrigeration temperatures and packaging in a modified atmosphere, combined with new preservation techniques such as bioprotection, can be used to protect thermally processed products and ensure their shelf-life. The target of this study was to select bacteriocine-producing starter lactic acid bacteria as bioprotective cultures, with the aim of limproving the shelf life of sliced cooked ham packaged in modified atmosphere. After being isolated, purified and preliminary tested to evaluate their non-spoilage activity, the strains of four bacteriocin-producing lactic acid bacteria of Lactococcus lactis, were used in different tests both individually and in combination with some spoilage consortia within the sliced cooked ham packaged in modified atmosphere. After 10 weeks from the inoculum, hams inoculated with starters and consortia individually and in combination by spraying and stored at 7 °C in modified atmosphere packaging, were sampled to determine the microbial charge developed inside. The DNA of all samples was subjected to PCR amplification and sent to Illumina sequencing to evaluate the nature of the microorganisms inside the packages of sliced cooked ham; there were also evaluate interactions and inhibitions between these microorganisms.