BACTERICIDAL AND BACTERIOLYTIC EFFECTS OF SELECTED FOOD-GRADE PHOSPHATES, USING STAPHYLOCOCCUS-AUREUS AS A MODEL SYSTEM

Phosphates have been approved for use in meat products primarily to pr otect flavor and increase yields. It also is known that phosphates hav e antimicrobial properties. The objective of this study was to compare the effects of different phosphates in a model system. Minimum inhibi tory concentrations (MICs) of selected food-grade phosphates added to early-exponential-phase cells of Staphylococcus aureus ISP40 8325 in a synthetic medium were determined to be 0.1% for sodium ultraphosphate and sodium polyphosphate glassy and 0.5% for sodium acid pyrophosphat e, sodium tripolyphosphate and tetrasodium pyrophosphate. Thus, the MI C values for the very long chain-length phosphates were lower than the MIC values for shorter chain-length phosphates. Leakage of intracellu lar nucleotides was observed both spectrophotometrically (release of A 260-absorbing material) and microscopically (appearance of gelatinous cellular aggregates). Treatment of the gelatinous cellular aggregates with DNase, RNase and proteinase indicated that the aggregates contain ed DNA, RNA and protein, thus indicating cellular lysis in the presenc e of phosphates.