FIG 4.
Characterization of phage HU1. (a) Thermal stability of HU1. Each residual activity was normalized with that of 25°C, as its value was 1.0. The values of 60, 63, and 70°C were below the detection limit (10−5). The asterisk represents the thermostability of HU1 at 63°C when incubation was conducted for only 30 min, corresponding to the conditions of pasteurization. (b) pH stability of HU1. Each residual activity was normalized with that of pH = 7, as the value was 1.0. The values of pH = 3 and pH = 11 are below the detection limit (10−3). (c) Plaque-forming abilities of HU1 at each temperature, normalized with that at 25°C, as the value was 1.0. The values at 30 and 35°C were below the detection limit (10−5). Data are expressed as average values ± SD (n = 3).