Effects Of Different Preservative On Quality Of Agaricus Bisporus In Logistics Transportation

Agaricus bisporus was the largest cultivated edible fungus in the world,accounting for 70%of total edible fungus production due to its unique flavor,high nutrition,and low calories.With the acceleration of domestic circulation and the continuous increase of international import and export quantity,the demand for long-distance trade and long-distance transportation of mushrooms is growing.However,mushrooms have no protective tissue on its surface,which is easily susceptible to mechanical damage during transportation,thus leading to microbial contamination and browning,which affects its quality and sales value.So,it’s a problem to prevent the quality loss and quality deterioration during the logistics transportation of mushrooms.In this study,according to the effect of vibration on the quality of mushrooms,the conditions of vibration damage were determined.And the mechanism of mechanical damage alleviation by exogenous spraying of CaCl₂ and polyethylene glycol on mushrooms was clarified through the changes of cell wall metabolism of phenylpropanes,antioxidant metabolism and product content.The main results are as follows:（1）Mushrooms were stored at 10±1℃ after being vibrated at 2,3 and 4 Hz for 2,4and 8 h,respectively,with non-vibration treatment as the control.The changes in appearance,the total color difference（ΔE）,hardness,weight loss rate,malondialdehyde（MDA）,relative electrical conductivity,total phenol,polyphenol oxidase（PPO）activities and vitamin C（V_C）of mushrooms during storage were measured.The results showed that when the vibration frequency was 2 Hz,the quality of mushrooms was not significantly damaged even 8 h treatment.When the vibration frequency was 3 Hz,the quality of mushrooms decreased gradually with the extension of vibration time during storage,especially the shelf life of mushrooms was greatly shortened by 3 Hz 8 h treatment.When the vibration frequency was 4 Hz,the quality of mushrooms was seriously damaged even if treated for a short time（2 h）,mainly manifested as brown spots on the lid accompanied by an increase inΔE value,fruit body softening and decreasing in hardness,MDA content and relative electrical conductivity constantly increasing,PPO activities increasing but V_Ccontent significantly decreasing.This study provides a theoretical basis for the definition of damage threshold on mushrooms in logistics transportation and further research on transportation damage control measures.The initial threshold of damage to mushrooms was determined to be 3 Hz vibration treatment for 8 h.（2）The effects of exogenous CaCl₂ on the organoleptic appearance,nutrient composition,reactive oxygen species（ROS）,cell wall components,and degradative enzyme activity of mushrooms during storage after simulated vibration.The results showed that exogenous CaCl₂ treatment could delay mushroom browning and softening during storage after vibration and reduce the contents of superoxide anion（O₂.^-）and hydrogen peroxide（H₂O₂）by 26.23%and 28.57%,respectively,by regulating the activity of antioxidant enzymes,thereby alleviating membrane lipid peroxidation.Theβ-galactosidase（β-Gal）activity was decreased by 63%and cellulase activity was inhabited by CaCl₂ treatment,thus delaying the degradation of cell wall components.CaCl₂treatment enhanced cinnamate 4-hydroxylase（C4H）and 4-coumaric acid:Co A ligase（4CL）activities,increased the contents of secondary metabolites such as total phenols and flavonoids by 7.82%and 46.25%,respectively,which was helpful to recover the mechanical damage caused by vibration during storage.（3）The effects of exogenous application of polyethylene glycol（PEG）on the organoleptic appearance,phenylpropane metabolic pathways,cellus formation,antioxidant enzymes activities,the components of cell wall and the activities of degrading enzymes of mushrooms during storage were studied.The results showed that 0.3%PEG treatment could activate the metabolic pathway of phenylpropane in advance,and the activities of phenylalnine ammonialyase（PAL）and 4CL were up-regulated by 93%and 52%,respectively,while the activity of C4H was increased by 21 times.By regulating the activity of antioxidant enzymes in cells,coordinating the metabolic pathways of active oxygen and phenylpropane,and generating secondary metabolites with antioxidant activity.Where,the lignin content was increased by 156%,which accelerated the lignification of damage cells and helped alleviate mechanical damage caused by vibration during storage.