THERMAL INACTIVATION OF LACTOBACILLUS PLANTARUM IN A MODEL LIQUID FOOD

Abstract

ABSTRACT Thermal process is one of the safest and most frequently used methods for food preservation. The use of model food in thermal treatment studies has several experimental advantages and enables reproducibility. Correct physical characterization of the model food and determination of thermal resistance of microorganisms are essential requirements in thermal treatments experiments. The present work determined the rheological characteristics of a 0.3% (w/w) carboxymethylcellulose (CMC) suspension, used as model liquid food, and the thermal resistance of Lactobacillus plantarum, a target microorganism in pasteurization processes. The rheological characterization was conducted using a double wall concentric‐cylinder rheometer with controlled stress, at various temperatures ranging from 25 to 80C. The L. plantarum thermal resistance was evaluated using the three‐neck flask method, at 52, 55, 58 and 61C. The rheological behavior of the model food was adjusted to the power law, with pseudoplastic behavior, consistency index (k) of 0.09Pa·sn and behavior index (n) of 0.80 at 25C. The parameters Ak and the activation energy (Eak) of the Arrhenius model were 0.0003Pa·sn and 14,140.7 J/mol/K, respectively. The values of D52C, D55C, D58C and D61C of L. plantarum were 76.3, 36.7, 16.4 and 7.3 s, respectively, with a z of 8.9C. The results showed that the model food system evaluated in this work represents several types of fruit juices. The use of well‐characterized model food systems could greatly improve experimental consistency and reproducibility of thermal process studies, which are characteristics highly desirable but still scarce in the literature.PRACTICAL APPLICATIONSThe use of model food in the study of thermal process is highly desirable, but there is limited information in the literature on the characterization of model food systems associated with inactivation kinetics of microorganisms. The carboxymethylcellulose suspension described in this work can be used as a fruit juice model. The thermal inactivation of Lactobacillus plantarum proposed in this model is suitable for thermal process studies and design. The data on the model liquid food system and thermobacteriology described in this work are potentially useful for future studies on food thermal processes and represent a contribution to the development of efficacious food processing protocols.