Optimization of Haskap Extract and Tannic Acid Combined with Mild Heat Treatment: A Predictive Study on the Inhibition of <i>Cronobacter sakazakii</i>

Cronobacter sakazakii is an opportunistic food-borne pathogen that causes severe infections with high morbidity and mortality rates in neonates, the elderly, and immunocompromised individuals. The plant extracts containing natural antibacterial compounds are currently under consideration as alternatives to synthetic artificial preservatives for the control of C. sakazakii. There has been increasing interest in using plant-derived antimicrobials in combination with mild heat to control pathogens in preservative-free foods. In this study, the individual and combined effects of four independent variables, i.e., polyphenol-rich haskap extract (HE) concentration (2-10%), tannic acid (TA) concentration (0.1-0.5), temperature (35-55 degrees C), and time (1-5 min), on C. sakazakii inactivation were investigated by response surface methodology (RSM) with a five-level four factor central composite design (CCD) and an optimal combination for maximum inhibition was determined. The statistic metrics of R-2, R-adjusted(2), R-predicted(2), coefficient of variation (CV), Predicted Residual Error Sum of Squares (PRESSs), adequate precision, and lack-of-fit were used to reveal the prediction performance. The results revealed that all the independent variables, except time, influenced C. sakazakii inactivation. Among the independent variables, the temperature was the most effective variable (p < 0.0001) as regards inactivation. The synergistic effects of HE with TA and temperature were observed. Many possible optimum conditions of mild heat treatment that maximized the inhibition of C. sakazakii were obtained. The findings indicated that two distinct combinations were identified as the most effective inhibition of C. sakazakii: high concentration at low temperature and high temperature at low concentration. It can be concluded that haskap polyphenol extract, alone or in combination with tannic acid, has the potential to be used as a natural preservative to reduce the risk of C. sakazakii.