Isolation of Lactobacillus Strains from Siahmazgi Cheese to Study their Protective Behavior after Inoculation in Fermented-Sausage Model Medium

Introduction: Lactic acid bacteria (LAB), economically an important group of bacteria for food production, has been used as starter culture in the production of fermented sausages. Isolation and screening of microorganisms from naturally occurring processes have been the most common means for obtaining beneficial cultures for scientific and commercial purposes. Fermented sausages have traditionally been produced by spontaneous ripening with LAB, since the indigenous LAB originating from fermented meats are well adapted to the conditions of meat fermentation.

Purpose: The aim of this study was to evaluate the LAB strains isolated from Siahmazgi cheese to determine their suitability for use as starter cultures in fermented-sausage production.

Methods: Seventy-one LAB were isolated from a sample of Siahmazgi, an Iranian traditional cheese. Lactobacilli were then screened for some technological properties such as rapid production of lactic acid, growth in different salt concentrations, gas production from carbohydrates, catalase activity and antimicrobial activity. Finally, the selected lactobacilli were tested for their growth profile in fluid model-medium modified according to the special conditions of fermented sausages.

Results: It was determined that these strains have particularly marked technological properties, being rapid acid producers and salt tolerant, and having antimicrobial activities against some Gram-positive and Gram-negative bacteria. Likewise they had capacity to grow, and to decrease pH values, under simulated conditions of fermented sausages. The lactobacilli were able to grow at a high salt concentration of 10%. They also showed antimicrobial activities against Listeria monocytogenes, Staphylococcus aureus and Escherichia coli. Acceptable souring properties and good growth properties in simulated fermented sausage medium were found for these isolates with maximum number 7.99 log CFU/ml.

Significance: We concluded that the isolates exhibited the best technological properties to act as starter cultures for manufacturing fermented meat products. This research confirmed the protective effect of Lactobacillus plantarum in a model sausage environment.