Investigation of the effects of food constituents on Bacillus subtilis reduction during high pressure and moderate temperature

Our published results and our studies for optimization of process conditions to inactivate Bacillus subtilis by high hydrostatic pressure and mild heat using response surface methodology indicated that the optimum process parameters for a six-log-cycle reduction of B. subtilis were obtained as temperature, 46 °C; pressure, 479 MPa; and pressure holding time, 14 min. Based on the results, response surface methodology (RSM) was employed in the present investigation, the effects of food constituents like soybean protein, soybean oil, sucrose, and pH of food matrix on the B. subtilis reduction during high pressure and moderate heat was studied, and a quadratic polynomial predictive model for the effects of food constituents and pH of food matrix on B. subtilis reduction during high pressure and moderate heat was built with RSM accurately. The experimental results showed that the efficiencies of B. subtilis reduction in milk buffer and food matrix designed in the present work, under the condition of high pressure treatment process parameters described above, had some differences. The soybean protein (P < 0.0001), sucrose (P < 0.0001), and pH (P = 00006) significantly affected reduction of B. subtilis. The effect of soybean oil on reduction of B. subtilis was not significant (P = 0.8363). The adequacy of the predictive model equation for predicting B. subtilis reduction in food matrix by high pressure and moderate heat was verified effectively using experimental test date that was not used in the development of the model.