The mechanisms controlling heat and mass transfer on frying of beefburgers. Part 2: The influence of the pan temperature and patty diameter

The effects of varying pan temperature and meat patty diameter on heat (temperature at the centre (5 mm) and 2 mm below the surface) and mass transfer (total, water and fat loss) of beefburgers prepared by double-sided frying were studied. The porosity of the fried beefburgers was determined based on the volume shrinkage and density measurements. The thawing time measured at the centre of the beefburger, total frying time and the final temperature 2 mm below the surface were significantly influenced by pan temperature, whereas the choice of meat raw material was of less importance than the pan temperature for the heat transfer. The characteristics of heat transfer, i.e. thawing and total frying time, were significantly influenced by the original patty diameter, with faster temperature increase in the smaller beefburgers. The most determinant factor for the water flux is the temperature gradient, and for the fat flux, the fat content. The water loss based on the initial water content in the form of drip was about 80% of the water loss even at a pan temperature of 175 °C. This means that the pressure-driven water loss is the main mechanism governing the water loss in the frying of beefburgers. The higher the heat penetration by using beefburgers of the smaller diameter and the higher the cooking temperature that induces higher water losses, the faster is the crust formation, which in turn results in less shrinkage and higher porosity of the heat-processed meat. When beefburgers of different diameters were studied the porosity was dependent both on the rate of heat transfer and on the amount of water and fat flux and was higher with increasing water and fat flux.