Buzrul Sencer
Auditing Department, Tütün ve Alkol Piyasası Düzenleme Kurumu (TAPDK), 06520 Ankara, Turkey.
Foods. 2017 Sep 7;6(9):79. doi: 10.3390/foods6090079.
Modeling of microbial inactivation by high hydrostatic pressure (HHP) requires a plot of the log microbial count or survival ratio versus time data under a constant pressure and temperature. However, at low pressure and temperature values, very long holding times are needed to obtain measurable inactivation. Since the time has a significant effect on the cost of HHP processing it may be reasonable to fix the time at an appropriate value and quantify the inactivation with respect to pressure. Such a plot is called dose-response curve and it may be more beneficial than the traditional inactivation modeling since short holding times with different pressure values can be selected and used for the modeling of HHP inactivation. For this purpose, 49 dose-response curves (with at least 4 log reduction and ≥5 data points including the atmospheric pressure value ( = 0.1 MPa), and with holding time ≤10 min) for HHP inactivation of microorganisms obtained from published studies were fitted with four different models, namely the Discrete model, Shoulder model, Fermi equation, and Weibull model, and the pressure value needed for 5 log (₅) inactivation was calculated for all the models above. The Shoulder model and Fermi equation produced exactly the same parameter and ₅ values, while the Discrete model produced similar or sometimes the exact same parameter values as the Fermi equation. The Weibull model produced the worst fit (had the lowest adjusted determination coefficient (R²) and highest mean square error (MSE) values), while the Fermi equation had the best fit (the highest R² and lowest MSE values). Parameters of the models and also ₅ values of each model can be useful for the further experimental design of HHP processing and also for the comparison of the pressure resistance of different microorganisms. Further experiments can be done to verify the ₅ values at given conditions. The procedure given in this study can also be extended for enzyme inactivation by HHP.
通过高静水压（HHP）对微生物进行灭活建模需要在恒定压力和温度下绘制微生物计数对数或存活率与时间数据的曲线。然而，在低压和低温值下，需要很长的保持时间才能获得可测量的灭活效果。由于时间对HHP处理成本有显著影响，因此将时间固定在适当的值并根据压力量化灭活效果可能是合理的。这样的曲线称为剂量反应曲线，它可能比传统的灭活建模更有益，因为可以选择不同压力值下的短保持时间并用于HHP灭活建模。为此，对从已发表研究中获得的微生物HHP灭活的49条剂量反应曲线（至少有4个对数减少且≥5个数据点，包括大气压值（=0.1MPa），且保持时间≤10分钟）进行了四种不同模型的拟合，即离散模型、肩部模型、费米方程和威布尔模型，并计算了上述所有模型5对数（₅）灭活所需的压力值。肩部模型和费米方程产生了完全相同的参数和₅值，而离散模型产生了与费米方程相似或有时完全相同的参数值。威布尔模型的拟合效果最差（调整决定系数（R²）最低，均方误差（MSE）值最高），而费米方程的拟合效果最好（R²最高，MSE值最低）。模型参数以及每个模型的₅值可用于HHP处理的进一步实验设计，也可用于比较不同微生物的耐压性。可以进行进一步的实验来验证给定条件下的₅值。本研究中给出的程序也可扩展用于HHP对酶的灭活。
