Optimizing Escherichia coli O157:H7 inactivation in goat's milk by thermosonication

Abstract

Escherichia coli O157:H7 (STEC) is one of the hazardous foodborne pathogens in milk. Although traditional preservation methods reduce contamination, they are time‐consuming or cause physicochemical changes. Therefore, we optimize STEC inactivation in goat's milk by thermosonication, an alternative to traditional treatments. Different times (1–35 min) and temperatures (45.9–74.1°C) were applied, using a Central Composite Rotatable Design (CCRD). Lipid oxidation was adopted as an optimization limiting factor. Mathematical models described STEC inactivation and lipid oxidation with high performance, considering the high R ² _adj (0.942 and 0.731), and low mean square error (0.065 and <0.0001) and lack‐of‐fit (0.133 and 0.183). Validation was verified by the accuracy (1.141 and 1.017) and bias (0.992 and 1.006) factors, and the relative error of prediction (0.910 and 1.000). Both variables affected STEC inactivation linearly, enhancing decontamination. Lipid oxidation was affected by time, increasing oxidation products formation. Optimization was achieved around 1–20 min/62–74°C, improving STEC inactivation (6.6 log CFU/ml) with minimal lipid oxidation (0.06 mg MDA/L). Therefore, thermosonication represents a promising technology facing to traditional methods, ensuring bacteriological safety and minimal alterations.

Practical Applications

Despite traditional methods for milk decontamination still being considered effective, there are some reports on pasteurized milk and dairy products‐related outbreaks. High‐intensity ultrasound is an emerging non‐thermal technology recently explored as a pathogen reduction method, used individually or combined. However, due to cavitation mechanism and free radicals realizing, some oxidative alterations could occur during processing. The present research paper contributes to provide a better understanding on the combined application of ultrasound and heat (thermosonication) to inactivate Escherichia coli in caprine milk. The findings herein are promising to the industrial utilization of thermosonication to obtaining safety products with minimal oxidative changes.