Efeito da alta pressão hidrostática sobre o crescimento de bactérias ácido lácticas e inativação de Salmonella enteritidis em presunto de peru

Abstract

In this study high hydrostatic pressure (HHP) at 400 MPa for 15 minutes at room temperature was applied to turkey ham followed by storage at 4, 8, 12°C. Lactic acid bacteria (LAB) growth data were adjusted to Modified Gompertz and Baranyi models at different storage temperatures. The same HHP operational conditions were applied followed by normal refrigerated (7°C) and abusive (13°C) storage conditions aiming at isolating, identifying and evaluating bacteriocin productions by LAB against Salmonella Enteritidis ATCC 13706, using MRS (Man, Rogossa and Sharp) agar and M-17 agar. Also the inactivation of such pathogen was evaluating by using either 300 or 400MPa in a continuous processing of 15 minutes or multiple cycles (2 cycles of 7.5 minutes; 3 cycles of 5 minutes; 5 cycles of 3 minutes) at room temperature. Following the HHP treatments the samples were stored at 4°C and carried out further evaluation of the pathogen recuperation. It was verified that the Gompertz Modified model better fitted LAB growth data at 4 and 12°C, while Baranyi model presented better adjustment at 8°C. It was also observed that pressurized samples showed higher commercial validity when compared to control samples. High pressure treatment even at abusive storage temperature allowed commercial validity of 42 days, while non pressurized control samples presented validity of 35 days. The Enterococcus sp and Streptococcus sp genera were identified as contaminant microbiote. The strains were able to produce inhibition halos against the pathogenic target, in the proportion of 91.6% of Enterococcus sp and 25% Streptococcus sp for control samples isolates, and 70.8% of Enterococcus sp and 8.3% of Streptococcus sp for pressurized samples isolated. By evaluation the HHP inactivation of 6.8 log10 CFU/mL, a decimal reduction of 1.5 log10 CFU/g was verified within 24 hours of refrigerated storage previously to the processing. The HHP continuous treatment at 300 MPa for 15 minutes lead to a reduction of 2.8 log CFU/g, while the treatments with 2 cycles of 7.5 minutes; 3 cycles of 5 minutes, and 5 cycles of 3 minutes, resulted in population decrease of 2.9 log, 2.9 log10 and 3.2 log CFU/g, respectively. On the other hand, treatments at 400 MPa both continuously or in cycles resulted in complete inactivation of the pathogen. Finally, by evaluating the recuperation of injured cells by HHP it was possible to observed that a higher recuperation was obtained through TAL (thin agar layer) methodology in comparison to XLD (xylose lysine deosxycholate agar) and TSA agar (trypticase soy agar), in samples stored at 10°C for 10 days. In overall, it was concluded that HHP was shown to be an efficient method for inactivating the target pathogen and spoilage microorganism, allowing a greater significant increase in the commercial validity.