Validation of mild cooking processes with target of Listeria monocytogenes inactivation to ensure food safety

Sammanfattning: This thesis investigates the use of Time Temperature Integrators (TTIs) to validate industrial cooking processes aimed to achieve a 6 logarithmic inactivation of Listeria monocytogenes, equal to a heat load of 2 min at 70 °C (P707.5 = 2) . To produce microbiological TTIs, live cells of L. monocytogenes were crossbound in alginate beads. Decimal reduction (D) values were measured in two food matrixes, meat extract and milk. D-values were compared in capillary tubes and in alginate beads. The results showed that the immobilised cells had slightly higher D-values compared with free cells in capillary tubes. Measurements in milk revealed higher D-values compared to measurements in meat extract. Alginate beads in milk showed a D58 of 4.5 min, compared to capillary tubes with a D58 of 3.7 min and alginate beads in meat extract a D58 of 1.5 min and capillary tubes a D58 of 1.0 min. Enzymatic TTIs based on inactivation of α-amylase (BAA70) were used for validation of a commercial fried fish burger production. The TTI was calibrated and had a D70 of 28.3 min and z of 6.5 °C ± 0.30 °C. The burgers were fried on both sides on a Teflon frying belt, before the burgers subsequently were heated in a continuous oven. The temperature profile calculated from a numeric model was combined with known inactivation kinetics and the residual α-amylase activity was calculated and compared to actual values of the TTIs placed in the core of the fish burgers. The results showed that α-amylase BAA70 TTIs can be used as to validate a specific minimum pasteurisation value for fried fish burgers.