A procedure for extracting staphylococcal enterotoxin from foods at elevated temperatures and low centrifugal forces

Abstract

Various low relative centrifugal forces (RCFs) were tested for their effectiveness in ‘cleaning up’ extracts of staphylococcal enterotoxin from food homogenates. RCFs of at least 10 000 × g were effective if centrifugations were for 30 min periods or longer. Below 8000 × g, and down to about 1000 × g, the cleaning up of extracts was effective only if centrifugation was preceded by filtration of food homogenates. Investigations of the thermal stability of enterotoxin during cleaning up of extract at higher than refrigeration temperatures showed that centrifugation temperatures of up to 40°C had little adverse effect on the serological activity of the toxin. Based on these findings a procedure was devised for extracting enterotoxin from foods using basic bench top centrifuge at ambient temperatures. Separation of enterotoxin from food proteins in the extract was achieved by carboxymethyl cellulose-column chromatography. Levels of enterotoxin A detectable by the microslide gel double diffusion method following extraction by this procedure were 2.5 ng/ml for milk, 2.5 ng/g for yogurt and 5 ng/g for cheese and corned beef.