Effects of different microwave power levels on chemical, physical and histological characteristics of beef roasts

Abstract

The objectives of this study were to determine (1) the effects of different meat masses on microwave oven efficiency, chemical and physical characteristics of semimembranous beef (SM) muscle roasts cooked by microwave heating, and (2) the effects of microwave power levels and final internal endpoint temperature on chemical, physical and histological characteristics of SM beef muscle roasts.

The results of power output and efficiency of microwave oven and load factor tests for water and meat were presented. The load affected the measured power output and oven efficiency. Different size meat masses cooked at different rates, as indicated by differences in cooking time per kg. When water mass was increased, the efficiency of the oven also increased. However, the efficiency of the oven was decreased as meat mass was increased at all microwave power levels. Therefore, actual power output would vary for different food items because of differences in specific heat.

Beef roasts (1.5 kg) were cooked to three internal endpoint temperatures (60, 70, 80$\sp\circ$C) using three different microwave power levels. Cooking time, standing time, post processing temperature rise, moisture, fat, protein, thiamin, water holding capacity, Instron measurement, and collagen solubility were determined. Myofibrillar tissue and collagen tissue were examined with both the light microscope and transmission electron microscope.

The use of variable power for microwave cooking of beef roasts does not result in measurably different chemical or physical characteristics. Histological examination of the ultrastructure of muscle and collagen revealed changes in sarcomere appearance and size that were related to internal endpoint temperature. Recommendations for microwave cooking of meat should take into account meat mass, desired endpoint temperature and post-cooking temperature rise.