Experimental And Theoretical Study Of Ultrasound's Influence On Food Freezing And Thawing Process

Freezing is an efficient preservation process because it can both preserve the best value of foodstuff and prevent the foodstuff from being contaminated. This method of preservation has been widely used in the world. But, it always is the major task that attracts widely attentions to study how to freeze and thaw the foodstuff efficiently and how to keep the foodstuffs quality well after food freezing and thawing process.We reviewed the historical development of the technology of food freezing and thawing, and its current study at home and abroad and analysed the factors that influence the foodstuffs quality in freezing and thawing process. Then ultrasound is put forward to be applied in food freezing and thawing process. In order to investigate the effects of ultrasound on food quality during the process, we finished some works as following:1 > At first, an experimental ultrasound freezing system was set up which can be used for studying food freezing and thawing process.2, The impact of ultrasound on supercooling degree of water was studied, and these results were compared to the supercooling degree of water under the same cooling condition without ultrasound's influence.3 N The food freezing process under the influence of ultrasound was studied, and the results were compared to the process under the same freezing condition without ultrasound's influence.4x We experimented the effects of ultrasound on thawing process, and discussed the difference between those and the other thawing process without ultrasound" influence.5 ^ After analyzing the ultrasonic thawing process based on heat transfer theory , we set up a theoretical model of the process. Program was carried out to simulate the ultrasonic thawing under different conditions. The impacts of frequency, intensity of the ultrasound and muscle fabric direction on thawing process were discussed. At last, some experiments were done to verify the theoretical model.This dissertation was supported by National sustentation fund of science (Authorized number: 50076039).