Study On The Influence Of Low-temperature-heating Methods By Microwave And Water-bath On Beef Properties

As the improvement of living standards, the need for nutrition and safety has been greatly increased. Sous vide is a kind of cooking techniques, which means cooking food at low temperature(50-80 ℃), to minimize the loss of water and nutrition and maintain color. Microwave heating technology has many advantages such as rapid, energy saving, nutrition and safety making people pursuing.In this study, by monitoring the center temperature of beef as experimental materials, the relationship between temperature and the time required is determined under low temperature condition. Taste, color, nutrition and safety of beef is compared under two low-temperature cooking. The main conclusions obtained are introduced as follows.(1) Using the fluorescence fiber thermometer and the thermocouple to monitor the center temperature of beef, the relation between center temperature and heating time was established. This provided data support for cooking menu of low-temperature microwave. Through monitoring center temperature of beef and recording power consumption, the study found: heating time was short for inverter microwave. When beef core temperature reached to 75 ℃, the heating time gap was 28.21 min. With reducing every 5 ℃, it could save 10 %-15 % electricity by inverter microwave. And it could save about 13 % electricity by water bath. The result of relation between center temperature and heating time provided guidance for the following experiments.(2) Using two different low-temperature heating methods, water retention rate, protein content, fat content, the free amino acid, the cooking loss and protein digestibility were studied. From the aspects and the relation between all aspects, it could be find that low-temperature heating method could retain the original ingredients effectively. Considering these aspects comprehensively, the heating methods of inverter microwave was better than the water bath.(3) Using two different low-temperature heating methods, Warner-Bratzler shear force, color and hardness level of sensory evaluation were studied. When beef was inverter microwave-heated at 65 ℃ for 4-6 min, the taste of beef was the best. When beef was inverter microwave-heated at 70 ℃ for 6-8 min, the color of beef was the best. It showed that beef organoleptic characteristic by inverter microwave heating was superior to by water bath.(4) Using two different low-temperature heating methods, the total number of colonies and Listeria sterilization of beef samples were studied. When beef was heated at 70 ℃, sterilization effect was good by two low-temperature heating methods. When beef was heated at 70 ℃, food safety could be ensured. Considering these aspects comprehensively, the heating methods of inverter microwave was better than the water bath. The heating temperature of 70 ℃ achieved safety standard of beef.(5) Using fitting the result of research, the optimum conditions of low temperature cooking methods was heating at 70 ℃ for 2-4 min for the beef by inverter microwave, which provided the basis for subsequent research.