Welcome to UW Madison Meat Science & Animal Biologics’ Hydrated Surface Lethality (HSL) Calculator.

The Hydrated Surface Lethality (HSL) Calculator is designed to enable processors, food safety professionals, and regulators to input time–temperature data collected from a thermal process, apply validated D- and z-values to estimate process lethality at the surface and the core of a product, and generate an integrated lethality report to confirm a process has achieved the required log reduction for the microorganism of concern. Internal/core lethality determination is based on the highly regarded and longtime used Meat Institute Foundation’s Process Lethality Spreadsheet found here.

Surface lethality is calculated with a similar approach following the premise that pathogenic bacteria are destroyed when the surface is wet (aka hydrated) and when lethal temperatures exist. The HSL tool supports several critical industry needs including providing a transparent, science-based method for evaluating whether a given process delivers sufficient lethality and an alternative approach to the humidity options listed in USDA, FSIS Appendix A. It can also be used to help identify gaps in marginal processes before they become regulatory or food safety concerns. We hope you find this tool useful for ensuring the thermal processing safety of your RTE meat products.

Access the HSL Calculator: https://hsl.meatsciences.cals.wisc.edu/