Preservation of red meat with natural antimicrobial peptides produced by lactic acid bacteria

[摘要] ENGLISH ABSTRACT: Red meat has a limited shelf-life at refrigerated temperatures, where spoilage is mainlydue to the proliferation of bacteria, yeast and moulds, acquired during the dressingprocess. In addition, almost a fifth of food-borne disease outbreaks, caused by microorganismssuch as Escherichia coli 0157:H7, Listeria monocytogenes andStaphylococcus aureus are associated with red meat. To improve the microbiologicalquality of red meat, systems such as HACCP, GHP and GMP are currently practiced;however, these practices are not able to extend the shelf-life of these products. Atpresent suitable food-grade preservatives are recommended, but the use of some ofthese preservatives is increasingly being questioned with regard to their impact onhuman health. Additionally, food service customers demand high quality products thathave a relatively long shelf-life, but still prefer the appearance of minimally processedfood. All these factors challenge the food manufacturing industry to consider morenatural means of preservation.Antimicrobial metabolites of food grade bacteria, especially lactic acid bacteria,are attracting increasing attention as food preservatives. Bacteriocins are antimicrobialpeptides (3 to 10 kDa) with variable activity spectra, mode of action, molecular weight,genetic origin and biochemical properties that are bacteriostatic or bactericidal tobacteria closely related and bacteria confined within the same ecological niche.Micro-organisms were isolated from beef, lamb and pork, obtained from fourcommercial retailers. The number of viable cells three days after the sell-by date at 4ºCranged from 80 cfu.g-1 to 1.4 × 108 cfu.g-1. Fifty-three percent were Gram-negativebacteria, 35% Gram-positive and 12% yeast. The microbial population of the meat wasgreatly influenced by the origin, i.e. the retailer. Bacteriocins produced by Enterococcusfaecalis BFE 1071, Lactobacillus curvatus DF 38, Lb. plantarum 423, Lb. casei LHS, Lb.salivarius 241 and Pediococcus pentosaceus ATCC 43201 were screened for activityagainst bacteria isolated from the different meat samples. Sixteen to 21% of theisolates, identified as members of Klebsiella, Shigella, Staphylococcus, Lactobacillus,Lactococcus, Leuconostoc, Enterococcus, Pediococcus, Streptococcus and Bacilluswere sensitive to the bacteriocins.Curvacin DF 38, plantaricin 423 and caseicin LHS (2.35 to 3.4 kDa) had thebroadest activity range and inhibited species of Lactobacillus, Pediococcus,Enterococcus, Listeria, Bacillus, Clostridium and Propionibacterium. The bacteriocinsremained stable at 121ºC for 20 min, in buffers with a pH ranging from 2 to 10 and inNaCl concentrations of between 0.1 and 10% (m/v). Like most peptides, they were sensitive to proteolytic enzymes. Curvacin DF 38 is sensitive to amylase, suggestingthat the bacteriocin might be glycosylated.To assess the efficiency of curvacin DF 38, plantaricin 423 and caseicin LHS asmeat preservatives, they were partially purified by ammonium sulphate precipitation andseparation in a Sep Pak C18 cartridge. The shelf-life of pork may be extended by up totwo days. Meat samples treated with bacteriocins were darker than the control(untreated) sample. Descriptive sensory evaluation by a seven-member panel indicatedthat there were significant differences (P ≤ 0.05) regarding the aroma, sustainedjuiciness, first bite and metallic taste attributes of the control and the 4 day-treatedsamples. The control and 2 day-treated samples and the 2 day- and 4 day treatedsamples did not differ significantly regarding these attributes. There were no significantdifferences regarding the initial juiciness, residue and pork flavour attributes.Concluded from the results obtained in this study, bacteriocins produced by Lb.curvatus DF 38, Lb. plantarum 423 and Lb. casei LHS effectively extended the shelf-lifeof pork loins by up to 2 d at refrigerated temperatures with no drastic changes onsensory characteristics. In edition, the stability of these bacteriocins broadens theirapplication as preservatives in many foods.

[发布机构] Stellenbosch University