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

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.