Microbial Successions Are Associated with Changes in Chemical Profiles of a Model Refrigerated Fresh Pork Sausage during an 80-Day Shelf Life Study

Abstract

ABSTRACTFresh pork sausage is produced without a microbial kill step and therefore chilled or frozen to control microbial growth. In this report, the microbiota in a chilled fresh pork sausage model produced with or without an antimicrobial combination of sodium lactate and sodium diacetate was studied using a combination of traditional microbiological methods and deep pyrosequencing of 16S rRNA gene amplicons. In the untreated system, microbial populations rose from 102to 106CFU/g within 15 days of storage at 4°C, peaking at nearly 108CFU/g by day 30. Pyrosequencing revealed a complex community at day 0, with taxa belonging to theBacilli,Gammaproteobacteria,Betaproteobacteria,Actinobacteria,Bacteroidetes, andClostridia. During storage at 4°C, the untreated system displayed a complex succession, with species ofWeissellaandLeuconostocthat dominate the product at day 0 being displaced by species ofPseudomonas(P. liniandP. psychrophila) within 15 days. By day 30, a second wave of taxa (Lactobacillus graminis,Carnobacterium divergens,Buttiauxella brennerae,Yersinia mollaretti, and a taxon ofSerratia) dominated the population, and this succession coincided with significant chemical changes in the matrix. Treatment with lactate-diacetate altered the dynamics dramatically, yielding a monophasic growth curve of a single species ofLactobacillus(L. graminis), followed by a uniform selective die-off of the majority of species in the population. Of the six species ofLactobacillusthat were routinely detected,L. graminisbecame the dominant member in all samples, and its origins were traced to the spice blend used in the formulation.