Studies On Frozen Process And Technology Of Four Special Vegetables

This article studied the freezing process of broccoli, pea pods, lentinus edodes and phaseolus vulgaris L. The effects of different blanching temperature and blanching times for the four vegetables' content of peroxidase were investigated with response surface methodology. Compared the changes of chlorophyll, texture and vitamin C with non-optimized process, optimized the current process of pretreatment. For controlling the temperature through thermocouple, studying the changes of idiosyneracy, considering the results under the electron-microscope, experimental results showed that the optimized pretreatment process was obtained. Furthermore, the changes of chlorophyll, texture and vitamin C after frozen were studied when treated with CaCl₂ in the broccoli's pretreatment process.First, the article introduced the source of this task, it was derived from "Study of super-excellence vegetable's key process and freezing equipment" that is the sub-task of "Study of key process and equipment of agriculture produce". That task is the national first ten-five "Tackle key problem". The task was to study the pretreatment process, frozen process, and the changes of cells' configuratiom with different treatments for broccoli, pea pods, lentinus edodes and phaseolus vulgaris L. and get the optimized technics-parameters. The first chapter reviewed the present situations and developing trend of quick frozen vegetables in China. The present developing situations of quick frozen vegetables in China, including export amount, species, producing area equipment and market situation are introduced in this paper; concerned about the fact that the international market has an increasingly high demand of food security and hygiene, the article also analysed the developing trend of quick frozen vegetables, and briefly discussed the bright research prospect in China.The second chapter is the research of broccoli's frozen process. The effects of different blanching temperature and blanching time on Broccoli quality were investgated with response surface methodology. The changes of chlorophyll and texture after forzen were studied when treated with CaCl2, and the optimization of pretreatment process was also researched. Experimental results showed that the optimized pretreatment process was asfollows: blanching time 2min, blanching temperature 96℃ and CaCl₂ 0.8%(m/v). Compared with the non-optimized process, it was found that the intensity of the texture for the bud increased 36.4%, caudex 16.8%; chlorophyll content 26.4%; peroxidase activity decrease to the level required by the process; Vc, protein content and water activity all had no significant change when treated the quick-freezing broccoli under the optimized pretreatment condition. Through the studies of the intensity of the texture for the bud and the caudex, the chlorophyll content, vitamin c in different frozen tempertureS, this experiment claimed that frozen temperature -40, frozen time 6.7 mins are the optimal parameters in broccoli frozen process.The third chapter is discussed about the pea pods's frozen process. The same is as the second chapter. The effect of different blanching temperatures and blanching times on produces quality was investgated with response surface methodology. The changes of chlorophyll and texture after forzen were studied after frozen, and the optimization of pretreatment process was also researched. Experimental results showed that the optimized pretreatment process was as follows: blanching time 48 seconds, blanching temperature 94.5°C. Through the observe of electron-microscope, the differences were not evident when pea pods were frozen in -30°C, -35°C and -40°C. In order to save energy source, this experiment claimed that frozen temperature -30°C, frozen time 4.8 mins are the optimal parameters for quickly-frozen process.The forth chapter is discussed about the lentinus edodes' frozen process. The effect of different blanching temperatures and blanching times for content of peroxidase was studied. The optimized blanching temperature was 93.6°C and blanching time 2.32 mins. Through the observe of electron-microscope, compared the differences after the lentinus edodes were frozen in -25°C, -30°C, -35°C and -40°C, the produce of-40°C frozen temperture were good. In order to keep the quality of produce, this experiment demonstrated that frozen temperature -40°C, frozen time 6.0 mins is better parameters of the lentinus edodes' frozen process.The fifth chapter is discussed about the phaseolus vulgaris L's frozen process. The effect of different blanching temperatures and blanching times for this vegetable content...