Kinetics of Physico-Chemical and Microbiological Changes During Storage of Commercial Frankfurters

Numerous changes occur in frankfurters during processing and storage. Reaction kinetics depends on various factors such as composition, temperature and packaging. Physico-chemical, microbiological and textural changes were analysed in two commercial formulations of frankfurters during their storage at 5, 10 and 15 C. This information allowed to calculate kinetics parameters and to predict shelf life at the usual storage temperature range. The formulation with higher content of meat protein was more resistant and elastic and had lower purge loss. The variability within each lot was higher than the effect of storage time and temperature on texture parameters, so these parameters would not be sensitive enough to detect changes and predict frankfurters shelf life. At 5 C, pH, acidity and purge loss remained constant with storage time while at 10 and 15 C good linear correlations (r> 0.958) were found. Microbiological growth fitted a logarithmic equation (r> 0.978). Physico-chemical changes followed a zero-order reaction while microbiological growth followed a first-order one. All reaction rate constants increased with temperature. Changes in pH, acidity and purge loss were higher for the formulation with higher starch and lower meat protein content. Shelf life at the normal storage temperatures could be predicted only from microbiological kinetic changes. Two brands of Frankfurter with different contents of protein (13.33 and 11.89 respectively) were used.