Enzyme testing (TTI)
Thermal Validation
Where conventional temperature probes cannot be applied, the enzyme technique TTI (Time and Temperature Integrators) may be used as an alternative thermal validation tool.
Heat sensitive enzymes encapsulated in a small capsule can be manipulated to have very similar thermal death kinetics to a target microorganism in foods. This means that the surviving level of these enzymes, after exposed to a given thermal process, indicates the surviving level of the target microorganisms. After heat treatment, the activity level of the surviving enzyme can be quantified by its ability to hydrolyse a substrate to give a colour compound that can be quantified by a spectrophotometer. By measuring the enzyme activity before and after heat treatment, a pasteurisation value for the target organism can be determined.
Because of their small size, the enzyme capsules can be applied at specific locations in foods, or attached to food contact surfaces, e.g. hot fill processes. TTIs can also be made and applied in large numbers, so that multiple measuring points can be achieved.
There are limitations of the technique, for example, the enzymes are only capable of measuring in the range between 60-95˚C. Results become less reliable outside of this temperature range.