Study On Effects And Mechanism Of Softening In Shiitake Mushroom Affected By Postharvest Environment

Shiitake mushrooms(Lentinula edodes(Berk.)sing)are widely cultivated and consumed edible mushrooms in China.Due to its delicious taste and rich nutrition,the production of shiitake mushrooms leap into the first rank in China.Used as an ingredient,Shiitake mushrooms have been welcomed by more and more consumers.Since the metabolic rate of Shiitake mushrooms is high,it will soon be dehydrated,softened and rotted after harvesting.Therefore,it has a short shelf life and its quality suffers with the extension of time.This study uses physical,chemical and biological methods to treat shiitake mushrooms in order to build a softening model.Within the softening model,the softening mechanism of shiitake mushroom is elucidated,which provides a theoretical basis for further researches on mushroom preservation.Besides,the methods used in this study can be applied to prolong the storage time of shiitake mushrooms.The major findings are listed as follows.1.After screening different packages,ultrasonic treatment,UV-C treatment and chemical treatment,a softening model using composition package with high barrier property was established.The results show that the shiitake mushrooms in softening model is significantly softer than the shiitake mushrooms in the control group which is treated by PE packages.2.Compared with the control group,the physiological and biochemical indexes of the softening model reveal the main mechanism of shiitake mushroom softening,that the high metabolic rate lead the higher activity of cell wall degradation enzymes.As a result,cell wall polysaccharides(CWPS)and chitin degrade.3.Compared with the control group,the transcriptome of softening model shows that the genes are up-regular in energy metabolism and polysaccharide or glycosaminoglycan metabolism pathway,such as cellulose,chitin,glucan,xylan and pectin,which indicates that the softening of shiitake mushroom is transcriptionally regulated to a great extent.4.40KHz,80 W/L,20min ultrasonic treatment can efficiently maintain the firmness of shiitake mushroom during storage.The main mechanism is to reduce the metabolism rate,maintain the cell wall chemical composition,and activate the antioxidant enzymes.In conclusion,the softening mechanism of shiitake mushroom is explained from physiological,biochemical and molecular perspectives,which builds a foundation for further research on texture regulation in shiitake mushroom preservation.In addition,ultrasonic treatment is proven to be effective in inhibiting the quality loss of shiitake mushroom.