EFFECT OF WATER ACTIVITY ON HIGH HYDROSTATIC-PRESSURE INHIBITION OF ZYGOSACCHAROMYCES-BAILII

Zygosaccharomyces bailii inhibition was evaluated in model systems wit h initial water activity (a(w)) ranging from 0.998 to 0.900 and expose d to a high hydrostatic pressure (HHP) treatment of 345 MPa at 21 degr ees C for 5 min. The yeast was completely inhibited (<10 cfu ml(-1)) a fter the HHP treatment when the a(w) was higher than 0.98. As the a(w) of the model system decreased, the number of surviving Z. bailii incr eased. For a(w) 0.92, 0.91 and 0.90, the HHP treatment reduced the ini tial inocula less than 1 log-cycle. The baroprotective effect of reduc ed a(w) on microbial inhibition by HHP was described by a linear relat ionship between the water activity depression factor (1 - a(w)) and th e log of the survival fraction.