Adequacy of Petrifilm™ Aerobic Count plates supplemented with de Man, Rogosa & Sharpe broth and chlorophenol red for enumeration of lactic acid bacteria in salami

Abstract

The present study aimed to assess the performance of alternative protocols to enumerate lactic acid bacteria (LAB) in salami. Fourteen cultures and two mixed starter cultures were plated using six protocols: 1) Petrifilm™ Aerobic Count (AC) with MRS broth and chlorophenol red (CR), incubated under aerobiosis or 2) under anaerobiosis, 3) MRS agar with CR, 4) MRS agar with bromocresol purple, 5) MRS agar at pH 5.7, and 6) All Purpose Tween agar. Samples of salami were obtained and the LAB microbiota was enumerated by plating according protocols 1, 2, 3 and 5. Regression analysis showed a significant correlation between the tested protocols, based on culture counts (p < 0.05). Similar results were observed for salami, and no significant differences of mean LAB counts between selected protocols (ANOVA, p > 0.05). Colonies were confirmed as LAB, indicating proper selectivity of the protocols. The results showed the adequacy of Petrifilm™ AC supplemented with CR for the enumeration of LAB in salami.