Studies On The Technology And Mechanism Of Extending The Shelf-life Of Agrocybe Chaxingu By Using MAP With Silicon Gum Film Window

Agrocybe chaxingu is a newly developed valuable edible mushroom. It is rotten easily at ambient temperature, and difficult to store. So far the study on the mushroom is mainly focus on the cultivate technology and its functional factors. Not much research on the preservation of Agrocybe chaxingu has been reported. In this study,MAP with silicon gum film window(MAPW)was used to store Agrocybe chaxingu, and the effects were obviously, which prolonged the shelf life of Agrocybe chaxingu to more than 20 days.The changes of physiological characteristics during storage were discussed, and the effect of these changes to the storage quality of Agrocybe chaxingu was analyzed in this paper, which provides a theoretical basis for the selection of storage method and determination of storage conditions. It was found from the experiments that the the lowest limit of O₂ concentration for storing Agrocybe chaxingu was 1.1%, and the anaerobic respiration would occur if the O₂ concentration was lower than the minimum value. Among these storage methods, the quality of Agrocybe chaxingu stored by MAPW was the best, with longest storage period and no chemical pollution. It is a good method for Agrocybe chaxingu storage.In order to improve the storage effect of MAPW, 3 factors (initial gas composition, silicon gum film window area of packaging and storage temperature) which strongly affect the physiological characteristics during storage were selected as the study objects. The effects of these factors on the gas environment of the packages, loss rate of Ascorbic acid, titratable acidity, changing of soluble solids, increasing rate of cell membrane permeability and decreasing of sensory quality during Agrocybe chaxingu storage period were explored. On the basis of these study, Ascorbic acid retention and sensory evaluation scores were set as response value, 3-factor and 3-level of response surface analysis was designed. The best parameters of MAPW for Agrocybe chaxingu storing were acquired: initial gas compositions were 5%O₂ and 10%CO₂, silicon window area of packing was 0.9cm2 and the storage temperature was 3℃.Taking conventional MAP as control, the effect of MAPW storage on the quality of Agrocybe chaxingu was studied. The Agrocybe chaxingu stored by MAPW had low respiration rate, low respiratory substrate consumption, so the total sugar content kept a relatively high level; cellulose enzyme of Agrocybe chaxingu stored by MAPW had higher activity, the increase of coarse fiber content was relatively slow. The coarse fiber increases was 62.8% that of control after 20d storage. During the whole storage period, the protein content and total amino acids content only decline a little, and free amino acids content increased a small amount either. These indicated that the protein metabolism was basically in a equilibrium state; It was found by light microscope and electronic microscope analysis that the microstructure and ultrastructure of Agrocybe chaxingu stored by MAPW changed slower than that of the control. The network structure could keep a relatively long time; Most of the hollow structure of the thread-like cell of fugai could be maintained, the uniform distribution and orderly arrangement were basically not destroyed.Compared with conventional MAP storage, high permeability of the silicon gum film window ensured the exchange of gas in the packing with surrounding atmosphere. Ethylene gas generated during the Agrocybe chaxingu storage could be exhausted in time, avoiding the hydrolysis of protein in high concentration Ethylene gas environment, cell membrane could be protected, thus the membrane system was more integrity. The activity of free radical scavenging enzymes of MAPW stored Agrocybe chaxingu was apparently higher than that of control. It could scavenge the free radical more effectively, so the generation and extinction mechanism of free radical could keep balance for a longer period, decreasing the hurt from free radical, the storage period of Agrocybe chaxingu could be extended. By analyzing and comparing the change rules of O₂ and CO₂ concentration in the MAP packing, enzymes Kinetic Model was selected to descript the characteristics of respiration rate during Agrocybe chaxingu storage. The model parameters are calculated. The respiration models at 3 and 7℃for MAPW stored Agrocybe chaxingu were acquired; Comparison of the experiment value and calculated value showed that the models have good application effect.