Crude Phenolic Extract effects in vitro and their impact in a raw sausages storage test. Preliminary findings

The vegetation waters (VW) could be considered as additional resources for the virgin olive oil (VOO) industry. In fact several phenolic compounds occurring in VW, having the same chemical characteristics of VOO phenols, possess many biological properties that include antioxidant and antimicrobial activity and, for this reason, may be used in food industry as natural preservative. The aim of the study was to assess:a) the in vitro effect of the Crude Phenolic Extract (CPE) obtained by ultrafiltration methods from VW on the growth of several food-borne strains and starter cultures; b) the overall impact of their inclusion in the raw sausages during a storage test. Antibacterial activity (0.375÷12 mg/ml CPE final concentrations) was based on the agar diffusion assay in comparison with the MBC (Minimum Bactericidal Concentration; microtitre assay) The microbial genera tested were: Staphylococcus (n.5), Listeria (n.4), Escherichia (n.2), Salmonella (n.1), Pseudomonas (n.3), Lactobacillus (n.2) and Pediococcus (n.1). Fresh pork raw sausages(shoulder and belly cuts, 1.5% NaCl, without) were manufactured, according to local recipe to obtain 3 experimental batch: C control, LL0.75 g/kg and HL 1.5g/kg of CPE. The two levels of polyphenol inclusion were based on the results provided by the antibacterial activity linked with the sensory analysis (e.g., lowest level of perceived flavours with antibacterial activity).The sausages were submitted to microbiological analysis in order to evaluate the total aerobic mesophilic and psycrotrophic flora, lactic acid bacteria (LAB), the Micrococcaceae, Staphylococcus spp., Pseudomonas spp., yeast and mould. The change of micro flora composition during a storage period of 15 days (4.0±0.5 °C) was evaluated, furthermore pH, water activity (Aw) and NaCl content were measured. The main in vitro results indicated that S. aureus and L. monocytogens showed the lowest level of resistance to CPE (1.5 – 3mg/ml) for both MBC and agar diffusion assay. In contrast the Gram negative strains were unaffected by the tested doses on agar assay whereas the MBCs ranged between 6 to 12 mg/ml.Starter cultures were dramatically reduced on growth (e.g. S. xylosus; MBC 0.75-1.5 mg/ml).The effect of polyphenol in fresh sausages was also evaluated demonstrating a relevant impact in the resident microflora.CPE inclusion influenced the development of microbial numbers, especially the Micrococcaceaeand Staphylococcus spp. counts, during 15 days at 4°C. LAB counts and psycrotrophic flora were affected only in the HL sausages. During the shelf life NaCl varied from 1.5 to 2.2%, meanwhile Aw decreased from 0.970 to 0.945 for C and LL and to 0.938 in HL; pH ranged from 5.9 to 5.7 for C meanwhile for LL and HL the acidification was not appreciable. CPE delayed microbial growth without influenced on sensorial characteristic. Preventing lipid oxidation in raw and cooked sausages should be evaluated.