Study On The Preservation Mechanism And Technology Of Coprinus Comatus

The Coprinus comatus is a kind of green edible food,it have particular flavour and rich nutrition.Lately year,the main processes for extending supply periods are canning,curing and drying.There is little fresh Coprinus comatus due to post-harvest problems,such as cap opening,browning,autolysis and cellulose lignification.Based on analysis the autolysis phenomena of Coprinus comatus,the dissertation systematic discussed the kinetic property of polyphenol oxidase(PPO)and the optimum storage temperature.And the coating and modified atmosphere packaging(MAP)preservation methods were used in the Coprinus comatus storage.The results were as follows:1,During the storing periods,the stipe significantly elongated,cap opening occurred after the stipe bursting the external veil,and brown patch and slide happened on the surface.With the increasing of the storage time,the brown patch area increased,the color turned into darker,and black juice overflowed gradually.The inoculation tests indicated that the microorganism was not the direct cause of the Coprinus comatus autolysis.The organization structure of Coprinus comatus was damaged due to the autolysis.And the breeding of the microorganism with the juice overflowing accelerated the decay of the Coprinus comatus.2,The autolytic index and several important physiological and biochemical factors during the natural senescence process of Coprinus comatus were studied.Results showed that the autolytic index,cell membrane permeability,the content of MDA and O₂,the Cx activity increased,protein content decresed with the evolution of senescence progress.And the POD, SOD activity increased in early stage then decreased later.The CAT activity kept stabile in early and decresed later.The autolysis of the Coprinus comatus was closely related to senescence through the analysis to data pertinence.3,The characteristics of polyphenol oxidase(PPO)activities of Coprinus comatus were discussed by spectrophotometer,including catalytic characteristics,the optimum temperature, the optimum pH,the thermostability and so on.It were also studied the effects of four kinds of inhibitors and the difference of PPO activity in different part.The results showed that the optimum pH and temperature of Coprinus comatus PPO were 5.0 and 20℃respectively,the PPO was inactivated at 100℃for 30 s.The reaction kinetic of enzymatic browning was accordant with Michaelis-Menten,the K_m and V_maxwere 0.64 mol·L^-1and 0.08 U·min^-1, respectively.The inhibitory effects on PPO activity were different among four inhibitors(i.e., citric acid,EDTA-2Na,vitamin C and NaHSO₃).Among them,Vc showed the strongest inhibitory effect.The PPO activity was gradually declined from pileus to basal stipe and the pileus has the highest activity.4,To obtain an optimum storage temperature for the Coprinus comatus,the relationship between the temperature and cap opening rate was established.The resuRs indicated that,the cap opening rate was related closely to storage temperature.Coprinus comatus stored at 1-3℃had lower cap opening rate.When temperature higher than 3℃,the cap opening and decay appeared after stored for 7d.Considering the effects of external factors and temperature fluctuation,the(1±0.3)℃was suggested as the optimum temperature.5,Coatings with food gums were used to extend the shelflife and keep the storage quality of the Coprinus comatus.Four food gums(i.e.,glucomannan,agar,sodium alginate and starch) were studied.Results indicated that the coatings not only inhibit the PPO activity and the lignification changes,but also effectively prevent the loss of water.When the apparent viscosity of the food gums solutions were the same,sodium alginate produced the best result. The lowest fibrosis mass fraction and PPO activity,the higest L value were revealed,and the moisture content was kept a stabile level.However,moisture condensation on the surface of Coprinus comatus was evident,the browning was aggravated and the storage quality was affected during the anaphase storage.6,Effects of the concentration of sodium alginate,citric acid and glycerin of the composite film on storage quality were investigated by the orthogonal experiment.The results showed that,at(1±0.3)℃,RH(95±2)%,the optimum conditions were as follows:the concentration of sodium alginate was 1.0%,citric acid was 1.0%,glycerin was 1.0%.Under those optimizing conditions,the Coprinus comatus could show positive sensory qualities and have acceptable commodity value after stored for 12 days.7,Effects of modified atmosphere packaging of various gas comoposition and different concentration of Coprinus comatus on storage quality were studied by the orthogonal experiment.The results indicated that,at(1±0.3)℃,the optimal preservation technological parameters were:5%O₂,8%CO₂ and added Coprinus comatus 120 g.It revealed that sensous quality evaluation was high,the fibrosis mass and PPO activity of Coprinus comatus kept low levels,storage time and shelf life of Coprinus comatus were effectively lengthen.