| Pleurotus eryngii have a high nutritional and economic value for its pleasant almond aroma and crisp texture. But postharvest Pleurotus eryngii, seperated from the culture medium, will consume a large amount of nutrients itself by vigorous respiration. This will result in a decline in sensory quality and the degradation of cell wall and flavor substances, causing the negative effect on flavor and chewiness. In addition, mushroom in sales produced a lot of reactive oxygen species, attacking biological macromolecules and leading to rapid aging, serious decay, short shelf life. In this paper, based on previous experiments, we choosed Pleurotus eryngii as target material and explored the effects of controlled atmosphere (CA,30% CO2+2% O2) on Pleurotus eryngii quality at 20-25℃ and 90%-95%RH (CK,0.03%CO2+21%O2). First, the multivariate analysis method was applied to discuss the correlation between the different factors and the ageing process of postharvest Pleurotus eryngii. And then, further experiments were designed to study the effects of 30% CO2+2% O2 on cell wall metabolism, active oxygen metabolism, glutamic acid metabolism of Pleurotus eryngii during shelf life.l.In preliminary experiments, based on sensory evaluation and malondialdehyde (MDA) content determination,30%CO2+2%O2 was selected as the better one for mushroom fresh-keeping than 3 other treatments (2%O2,10%CO2+2%O2,50%CO2+2%O2). And therefore we did further studies on Pleurotus eryngii treated with CA(30%CO2+2%O2) and air as control (CK,0.03% CO2+21%O2). In this chapter, The controlled atmosphere (CA,30%CO2+2%O2) effects on Pleurotus eryngii quality during shelf life at 20-25℃ and 90%-95%RH were analyzed by one-way analysis of variance, principal component analysis, correlation analysis, partial least squares regression, and path analysis (0.03% CO2 +21% O2 was used as check (CK)). The results showed that CA alleviated weight loss, inhibited the decrease of hardness, protein, total sugar content, and maintained the lower electrical conductivity and pH, contributed to higher light and sensory score of Pleurotus eryngii. PCA indicated that CA exhibited a significant influence on Pleurotus eryngii color, total sugar, hardness, protein, electrical conductivity, pH changed dramatically during storage, especially on color. Partial least squares regression and correlation analysis showed that the hardness, protein, total sugar, L*, h and quality were positive correlated significantly and the weight loss, a*, b*, electrical conductivity and quality were negative correlated significantly. Path analysis suggested that L* is the main affecting factor on quality of Pleurotus eryngii by exerting the direct (L*) and indirect (a*, b*, weight loss) influence. In conclusion, CA had effects on several physicochemical indexes of Pleurotus eryngii and mainly exerted an influence on color index(L*, a*,1b*).2. Under the condition of(20-25℃,90%-95%RH), CA exerted an influence on cell wall composition(proteins, polysaccharides, chitin), chewiness and ultrastructure of Pleurotus eryngii. Results showed that the CA delayed the degradation of cell wall proteins, polysaccharide, promoted the accumulation of chitin, maintained a better chewiness and the integrity and stability of Pleurotus eryngii cell wall. In conclusion. CA keep a good edible quality of Pleurotus eryngii through affecting mushroom cell wall composition.3.Under the condition(20-25℃,90%-95%RH), CA significantly induced an increase of the reactive oxygen species scavenging ability, inhibited respiration, delayed the membrane lipid oxidation. CA was better suited to maintaining mushroom sensory characteristics and delaying the O2.production rate during shelf life. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and in CA were significantly higher than those of the control. However, the cytochrome c oxidase (CCO) activity was not influenced by CA. The results suggested that CA could surpress lipid peroxidation and strength the antioxidant enzyme activities, but it exerted little influence on the CCO activity of Pleurotus eryngii.4. Under the condition(20-25℃,90%-95%RH), CA maintained the total free amino acids conternt(especially glutamic acid) and inhibited the activities of protease, glutamate synthase (GOGAT), proline dehydrogenase (PRODH), glutamate dehydrogenase (GDH).The result indicated that CA exerted an influence on glutamic acid metabolism-related enzymes to retain the glutamic acid content, which was helpful to keep a high level of umami taste and improve the commercial value of Pleurotus eryngii. |
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