Bioprotective extracts from lactic acid bacteria inhibit spoilage Lactobacillus sakei CRL1407 in refrigerated meat discs

Abstract

Meat is recognized as one of the most perishable food. The main cause for meat deterioration is the growth of microbes including spoilage and pathogenic bacteria. Vacuum packaging (VP), modified atmosphere packaging (MAP) and chill temperatures are commonly used for increasing the shelf-life of meat and meat products. Under these conditions, psychrotrophic facultative and strict anaerobic bacteria such as Listeria monocytogenes, Enterobacteriaceae, Brochothrix thermosphacta, Clostridium, and deteriorative lactic acid bacteria (LAB) can grow causing different types of spoilage. In addition, LAB species belonging to the genera Lactobacillus were associated with severe acidification, production of off-odor/taste compounds and slime. However, certain LAB are well known to produce antimicrobial compounds such as organic acids, hydrogen peroxide, antifungal compounds and bacteriocins that may be exploited in the biopreservation of foods. On these bases, this study aims to evaluate the effect of bioprotective extracts (BEs) from Lactobacillus curvatus CRL705 and Lactobacillus acidophilus CRL641 against exopolysaccharide (EPS) producer Lactobacillus sakei CRL1407 in discs meat under VP at 4 °C. Meat discs were aseptically obtained from the center of semimembranosus muscles. BEs produced by L. acidophilus CRL641 (BE-1) and L. curvatus CRL705 (BE-2) were purified (ammonium sulfate precipitation/solid phase chromatography). The disks were inoculated with L. sakei CRL1407 (103 CFU/g) and treated with combined and BEs alone. Then, they were vacuum packed and incubated at 4 °C during 38 days. Microbiological counts, antimicrobial activity, pH, humidity, color, and lipid oxidation were evaluated at regular intervals. L. sakei CRL1407 was able to grow in control samples up to 7.77 log CFU/g after 38 days while BE-1 and BE-2 reduced their growth by 2 and 1.35 logarithmic cycles, respectively. The combined BEs caused the greatest reduction in the spoilage microorganism growth (3.31 log CFU/g) at 38 days of incubation. The antimicrobial activity was detected in treated samples with BE-1 and BE-1+BE-2 until day 16, while with BE-2 only at the initial time. The pH values were kept constant in the discs treated with combined BEs, while a decrease in those treated separately was detected. However, the greatest drop in pH was observed in the control samples. The moisture content did not present significant differences between all the analyzed samples showing values between 68.18% and 65.93%. When the color was determined, only the discs treated with BE-1 and BE-1+BE-2 did not present a perceptible change. Similarly, the most effective treatment to prevent lipid oxidation of discs during storage was combined BEs. Thus, the combination of BEs from LAB as biocontrol agents and the use of conventional preservation barriers to prevent the growth of deteriorating species will contribute to the extension of fresh meat shelf-life without quality loss.