LONG-CHAIN POLYPHOSPHATES INHIBIT GROWTH OF CLOSTRIDIUM-TYROBUTYRICUMIN PROCESSED CHEESE SPREADS

The effect of novel food-grade long-chain polyphosphate formulations ( JOHA HBS sodium polyphosphate glassy, 69 +/- 1% P2O5, and two similar salts (HBS-1 and HBS-9) on the growth of Clostridium tyrobutyricum ATC C 25755 in liquid culture and in pasteurized, processed cheese spreads was evaluated. In broth, 0.1% polyphosphate was sufficient to inhibit vegetative growth of the organism. In addition, a panel of 21 other g ram-positive and 11 gram-negative bacteria were tested for their sensi tivity against the polyphosphates. Whereas 17 of the gram-positives co uld be inhibited by 0.05 to 0.3% polyphosphate, none of the tested gra m-negatives were affected. Two different cheese spread formulations (c heese blend A: 55% moisture, 47.2% fat in dry matter; cheese blend B: 55% moisture, 57% fat in dry matter) were fortified with 0.1% to 1.0% polyphosphates, inoculated with 5 x 10(5) (cheese blend A) or 2.5 x 10 (6) (cheese blend B) C. tyrobutyricum spores per gram, and incubated a t 35 degrees C for up to 7 weeks. Determination of viable cell counts was carried out at days 1, 9, 19, and 49 (cheese blend A) and 8, 16, 2 7, 35, and 50 (cheese blend B). While 0.1% polyphosphate had little ef fect, higher concentrations were increasingly inhibitory to growth fro m a spore inoculum, to cell multiplication, and to gas formation. With 0.5% polyphosphate, onset of growth was delayed for about 3 weeks in cheese blend A, while this concentration was able to inhibit the organ ism in cheese blend B. In view of the experimental parameters selected (high initial contamination level; intrinsic and extrinsic parameters optimized for growth of clostridia), 0.5% polyphosphate may be suffic ient to control C. tyrobutyricum growth under ''normal'' conditions, w here initial spore counts are rather low, and storage temperatures are usually at or below 20 degrees C. Moreover, clostridia were completel y inhibited by 1.0% polyphosphate, which clearly indicated the usefuln ess of these polyphosphates for prevention of butyric blowing in paste urized processed cheese spreads.