Effects Of Vibration Stress On Storage Quality And Postharvest Physiology Of Agaricus Bisporus

The storage quality of fruits and vegetables is reduced due to mechanical vibration during transportation,leading to extremely high loss rates.Agaricus bisporus is welcomed by consumers around the world,because of white color and tender,delicious in taste and rich in nutriton.However,Agaricus bisporus has no natural protective layer structure on the surface,it has a strong respiration,high sensitivity,and is easily infected by microorganisms and easily damaged.Therefore,it is easy to loss water,browning,nutrients are consumed quickly after harvest,and it is not resistant to storage.In this paper,Agaricus bisporus was used as the test material,the simulated transport vibration table was set as 180 r/min（3Hz）,and the mushrooms were vibrated for 0 h（control）,1h and 2h respectively,and then the storage at3℃.By studying the changes of appearance quality,texture properties,flavor substances,active oxygen metabolism and antioxidant activity,the effects of vibration stress on the storage quality and physiological changes of Agaricus bisporus after harvest were investigated.The main research results are as follows:1.The longer the vibration time is,the higher the weight loss rate and respiration rate will be during the storage period of mushroom,on the last day of storage,the weight loss rate of mushrooms in 2h vibration treatment group is the highest（up to 0.88%）.Moreover,the vibration stress accelerated the decline of firmness and springness,and the 2h vibration treatment group had the lowest whiteness（L value of mushrooms on the last day of storage was close to 80）,which accelerated the browning and aging degree of mushrooms,and decreased the commodity value.2.A total of 17 amino acids were detected in mushrooms.After the vibration treatment,the total amount of umami amino acids of mushrooms decreased,and the total amount of sweet amino acids also decreased but was higher than that of umami amino acids,while the total amount of tasteless amino acids did not change significantly.Moreover,the total amount of umami,sweet,bitter,tasteless amino acids and amino acids of mushrooms in the vibration treatment group were significantly lower than those in the control group at the end of storage.From the perspective of taste value,the umami taste value of mushrooms increased,while the taste value of sweet and bitter decreased,and the taste value of sweet and bitter of mushrooms that treated by vibration was generally higher than that of the control group.The contents of 5’-nucleotide increased first and then decreased,and the 5’-nucleotide of vibration treatment was higher than that of control group at the end of storage.On the last day of storage,EUC value and energy charge value of mushrooms in vibration treatment group were significantly lower than those in control group.3.Vibration stress stimulates the activity of SOD and CAT increased,and the scavenging ability of reactive oxygen species O₂^-and H₂O₂was stimulated,so as to maintain the balance of mushrooms body quickly.Although vibration stress promoted enzyme activity,this stress defense ability was always limited.Thus,the accumulation of reactive oxygen species of mushroom was accelerated,resulting in serious cell membrane damage,and increased the relative electrical conductivity and MDA content.4.The relative content of total phenols and flavonoids of Agaricus bisporus increased first and then decreased.Due to the stress response caused by vibration,it was significantly higher than the control group at the early stage of storage,and the peak content appeared in advance.The content of ascorbic acid decreased,the longer the vibration time,the faster the decomposition of ascorbic acid.Vibration stress induced the increase of APX and PPO enzyme activities of Agaricus bisporus,and accelerated the browning of mushrooms.The POD enzyme activity of mushrooms in the control group was generally higher than that of the vibration treatment group,so it was speculated that the POD activity in the experiment might be as a peroxide scavenger rather than a browning accelerator.Comprehensive the above results and sensory evaluation,the length of vibration time directly affects the quality of Agaricus bisporus.Vibration stress accelerates the respiration rate of mushroom,accumulates a large amount of reactive oxide species,and induces SOD enzyme and CAT enzyme activity to increase.The catabolism of antioxidant substances is accelerated,which induces APX and PPO enzyme activities to increase,and POD enzyme activity decreases,and the longer the vibration time,the more times the mushrooms rub and collide with each other,which accelerates the browning and softening of the mushrooms.The final result showed that under the condition of vibration frequency of 3Hz,the tolerable simulated transportation time of mushroom was only 1h,and the sensory scores of mushrooms in the vibration treatment group on the 6th day were lower than those of the control group on the 10th day,indicating that the shelf life of mushrooms in the vibration treatment group was shortened.So the transportation time of Agaricus bisporus should be as short as possible after harvest,and the loss of mushrooms should be reduced through suitable anti-vibration packaging.