Chitosan inhibits growth of spoilage micro-organisms in chilled pork products

The aim of this study was to develop novel preservation systems for chilled, comminuted pork products that are sold raw using the natural compound chitosan (polymeric ß -1,4- N -acetylglucosamine). In vitro testing showed that viable numbers of Saccharomycodes ludwigii were reduced by up to 4 log cfu ml⁻¹ on exposure to 0·05% chitosan in 0·9% saline at pH 6·2. Higher concentrations of chitosan (0·25 and 0·5%) were required to achieve similar levels of inactivation withLactobacillus viridescens, Lac. sake and Listeria innocua. Torulaspora delbrueckii and Salmonella enteritidis PT4 were resistant to chitosan at the concentrations tested in this study (up to 0·5%). Trials in real foods showed that dipping of standard and skinless pork sausages in chitosan solutions (1·0%) reduced the native microflora (total viable counts, yeasts and moulds, and lactic acid bacteria) by approximately 1–3 log cfu g⁻¹ for 18 days at 7°C. Chitosan treatment increased the shelf-life of chilled skinless sausages from 7 to 15 days. Addition of 0·3 and 0·6% chitosan to an unseasoned minced pork mixture reduced total viable counts, yeasts and moulds, and lactic acid bacteria by up to 3 log cfu g⁻¹ for 18 days at 4°C compared with the untreated control. The results indicated that chitosan was an effective inhibitor of microbial growth in chilled comminuted pork products.