EFFECT OF POLYPHOSPHATES AND NACL ON AEROMONAS-HYDROPHILA K144

Polyphosphates are multifunctional ingredients added to many foods, pa rticularly meat products. In addition to their moisture-binding proper ties, polyphosphates have been reported to inhibit various bacteria. I n the current study, four food-grade polyphosphates were evaluated for their effects on the growth of Aeromonas hydrophila K144 in both a mo del system and a food system. Since polyphosphates can interact with o ther food factors, effect of these compounds were studied at different NaCl levels and temperatures. The model system was BHI Broth modified by the addition of polyphosphates (sodium pyrophosphate, sodium tripo lyphosphate, Hexaphos, or Sodaphos) and NaCl; incubation was aerobic a t 5 or 28C. The food system was ground pork with NaCl and polyphosphat e added and inoculated with A. hydrophila. Individually, the polyphosp hates were relatively noninhibitory in both BHI broth and ground pork, but NaCl and temperature interacted with the polyphosphates in the mo del system to increase generation and lag times of A. hydrophila. In B HI broth, a combination of 2% of any of the polyphosphates tested and 3.5% NaCl inactivated the bacterium; this inactivation was temperature -dependent. By both a plating system and electron microscopy, the poly phosphate-NaCl combination was shown to injure the bacterium. In the g round pork, the polyphosphate-NaCl combination limited growth of the b acterium during refrigerated storage. These results suggest that polyp hosphates could be useful to control the presence of A. hydrophila in certain foods.