Bacteriological Evaluation of Alkali-Extracted Protein from Poultry Residues

Abstract

The effect of alkaline conditions (pH 10.5 for 30–60 min at 23°C) on the extraction of protein from mechanically deboned poultry residues (MDPR) was examined with respect to the general bacterial flora, coliforms and salmonellae. Standard plate counts decreased from 1.5 × 103 CFU/g in the MDPR to 2.0 × 102 CFU/g in the freshly extracted protein curd; coliform counts decreased from 4.9 × 101 MPN/g to 0. Coliforms survived only when the MDPR was mishandled for 5 h at 23°C before alkaline extraction whereas salmonellae appeared to be eliminated entirely, irrespective of preincubation abuse of the MDPR or introduction of increased levels of Salmonella infantis. Spoilage of the protein curds occurred in 14 days at 3°C but there was no increase in coliform numbers. Reappearance of salmonellae following storage was seen only in the protein extracted from MDPR inoculated with S. infantis. The destruction of salmonellae by pH 10 was confirmed in a tryptic soy broth model system, but only under ambient temperature exposure; neither growth nor destruction occurred at 3 or 10°C. It was concluded that alkaline extraction of protein from MDPR using the suggested operating conditions does not exaggerate any public health hazard involving salmonellae.