EFFECT OF POLYPHOSPHATES AND NaCl ON AEROMONAS HYDROPHILA K144

Polyphosphates are multifunctional ingredients added to many foods, particularly meat products. In addition to their moisture-binding properties, polyphosphates have been reported to inhibit various bacteria. In the current study, four food-grade polyphosphates were evaluated for their effects on the growth of Aeromonas hydrophila K144 in both a model system and a food system. Since polyphosphates can interact with other 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 tripolyphosphate, Hexaphos, or Sodaphos) and NaCl; incubation was aerobic at 5 or 28C. The food system was ground pork with NaCl and polyphosphate added and inoculated with A. hydrophila. Individually, the polyphosphates were relatively noninhibitory in both BHI broth and ground pork, but NaCl and temperature interacted with the polyphosphates in the model system to increase generation and lag times of A. hydrophila. In BHI 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 polyphosphate-NaCl combination was shown to injure the bacterium. In the ground pork, the polyphosphate-NaCl combination limited growth of the bacterium during refrigerated storage. These results suggest that polyphosphates could be useful to control the presence of A. hydrophila in certain foods .