Facing the D-Ilemma of Heat Resistance Parameters: From Pathogen Risk Assessment to Surrogate Selection Challenges in the Fruit Juice and Nectar Production.

Over the years, numerous D- and z-values have been published in the scientific literature. While these values initially appear to be valid criteria for assessing and comparing the heat resistance of different microorganisms under the same conditions or the same microorganism under different conditions, this is not always the case. This review presents a comprehensive overview of food safety in fruit processing, considering contamination routes and focusing on the selection of surrogates for key pathogens such as Salmonella spp. and Escherichia coli. Factors influencing heat resistance parameters, such as the experimental method, food matrix, mathematical model, and challenges of industrial upscaling, are explored. We critically assess the diversity and lack of methodological standardization in determining D- and z-values, showing the consequences for risk assessment and surrogate selection. Along with a review of methods used by scientists, the problem of different methods for calculating the decimal reduction time is highlighted, as well as the lack of specifications for the use of z-values. Additionally, this review proposes the use of the glass capillary method for testing bacterial thermal resistance in liquid foods, such as fruit juices and nectars, in order to standardize the methodology and facilitate comparisons across the literature.