Potassium Sorbate and Recovery of Pectinolytic Psychrotrophs from Vacuum-Packaged Pork

Abstract

Pork loins were divided into small roasts. Thirty roasts were uninoculated and 30 were inoculated by dipping in 1 % peptone water containing 100 Colony-forming units (CFU)/ml of pectinolytic Yersinia enterocolitica. Twenty-four each of the uninoculated and inoculated roasts were sprayed with or dipped in 5 or 10% solutions of potassium sorbate. All roasts were then vacuum-packaged and stored at 5°C. After storage for 1 or 21 d, three roasts from each group were examined for psychrotrophic plate count (PPC) and the 3-tube most probable number of pectionolytic bacteria. Counts of psychrotrophs on lean surfaces of untreated controls increased by nearly 3.4 log10. Numbers on sorbate-treated lean surfaces increased about 2.0 log10. Growth and differences in counts on fatty surfaces were less. Numbers of pectinolytic bacteria on lean surfaces of controls increased by nearly 2.0 log10, but numbers of pectinase producers did not change significantly during storage of sorbate-treated samples. Of 30 pectinolytic isolates identified from roasts stored 21 d at 5°C, 87% were Yersinia spp. and 13% were Klebsiella oxytoca. Since most of the pectinolytic isolates were psychrotrophs of public health significance, inhibition of their growth by sorbate is of particular importance.