Industrially Relevant Canning Trials with a Sterilisation Time-Temperature Integrator

Food sterilisation, i.e. heating to above 120 °C for several min, still remains a primary method of food preservation. Current time-temperature integrators (TTIs), used to assess the thermal impact, only work at pasteurisation temperatures (below 100 °C). The aim of this work was to develop and validate a sterilisation TTI using an α-amylase from the hyperthermophile Pyrococcus furiosus. Previous experiments have found that this α-amylase has a z value similar to that of Clostridium botulinum spores and the enzyme is sufficiently heat resistant to show a measurable residual activity after 30 min at 121 °C. Analysis found a D value of 24 min and a slightly variable z value of around 11 °C. The decrease in enzymatic activity from thermal processing was found after a F_121°C process of 5 min to be 67 %, and for a F_121°C of 30 min it was 12 %, thus making P. furiosus α-amylase a strong and relevant candidate for a sterilisation TTI. Trials with canned water and mango chutney as test materials have confirmed the potential application of the enzyme within an industrially relevant setting of a model reel and spiral retort. The thermal data showed that at low or marginal F_121°C values, of less than 15 min, the correlation between the TTI and thermocouple data was closely comparable (R ² = 0.96). The applicability of these TTIs over the range of industrial processes is also shown.