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The Study on Integrated Freshness Preservation of Agrocybe Aegerita

Author: JiangHongBo
Tutor: WangZeJin；LinQiXun
School: Fujian Agriculture and Forestry University
Course: Processing and storage of agricultural products
Keywords: Agrocybe Chashugu Storage temperature Storage quality Irradiation Low Oxygen Active Modified Atmosphere Packaging High Oxygen Atmosphere Packaging Moisture absorber Mechanism of Senescence
CLC: TS219
Type: Master's thesis
Year: 2007
Downloads: 317
Quote: 2
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Abstract


The Agrocybe Chashugu （Agrocybe aegerita） is a crude edible fungi, it have nutrition function, health protection function and particular flavour. Lately year, with the change of people’s consumptive idea, the market demand of fresh Agrocybe Chashugu enhanced gradually. In view of the post-harvest problems didn’t resolve very good in preservation and transit at the ordinary condition, such as browning, cap opening, water loss and cellulose lignification, this thesis discussed the kinetic property of polyphenol oxidase （PPO）, the relationship between storage temperature and cap opening rate, and the effects of radiation, low oxygen active modified atmosphere packaging and high oxygen atmosphere packaging on storage quality of Agrocybe Chashugu. The possible mechanism for the Agrocybe Chashugu preservation technology and theory were also studied by analysis the pileus ultra-structure and physiological-biochemical indexes. The results were as follows:1．The PPO activities were determined at 410nm with pyrocatechol as substrate in different pH, temperature and substrate concentration. The reaction kinetic equation was also established in this study, while the PPO activity of different parts of Agrocybe Chashugu were studied. The results showed that the initial rate of PPO presented a linear rising movement at lower concentration of pyrocatechol, then with the concentration increased it changed very little. The optimum temperature and pH value of Agrocybe Chashugu PPO were 50℃and pH4．0～5．0, respectively. The reaction kinetic of enzymatic browning is accordant with Michaelis equation, the KM andυmax were 2．59 mol/L and 0．127 U/min. In the different parts of Agrocybe Chashugu, the PPO activity was gradually declined from pileus to basal stipe, which showing a position gradient.2．To obtain an economic storage temperature for the Agrocybe Chashugu, the relationship between the temperature and cap opening rate was established. It was found that the cap opening rate related closely to storage temperature. Agrocybe Chashugu stored at 0～3℃had lower cap opening rate than other temperature. When temperature higher than 3℃, the Agrocybe Chashugu start decay after stored for 5 days. Through repeated tests, it revealed that the optimum storage temperature of Agrocybe Chashugu was 1±0．3℃.3．Effects of different doses of 60 Coγ-ray irradiation on cap opening rate, PPO activity, MDA content, fibrosis mass fraction, Vc Mass fraction of Agrocybe Chashugu were investigated. The results showed that 0．8kGyγ-ray irradiation combined with lower storage temperature could inhibit physiological metabolic activity effectively and retard the senescence rate, and keep higher Vitamin C mass fraction.4．Effects of active modified atmosphere packaging of the different concentration of Agrocybe Chashugu and various gas composition on Agrocybe Chashugu storage quality were investigated by L9 （34） the orthogonal experiment. The result indicated that, at storage temperature （1±0．3）℃, the optimal preservation effect of Agrocybe Chashugu was obtained at the following condition: added Agrocybe Chashugu 150g、1%O2and 8%CO2．It embody that hydrolyzed amino acids and fibrosis mass fraction and PPO activity of Agrocybe chashugu keep low level, storage time and shelf life of Agrocybe Chashugu u may effectively lengthen.5．Effects of different high oxygen concentration on quality of Agrocybe Chashugu were researched. Results indicated that 80% oxygen atmosphere packaging could effectively inhibit-physiological metabolize activity and retard the senescence rate of Agrocybe Chashugu. With the stored time prolong, dew on caps and inner surface of the bag were evident. So the kind and quantity of moisture absorber were selected in continue test. The optimum preservation conditions of "HOA + moisture absorber" packaging to Agrocybe Chashugu were studied by L16 （45） the orthogonal experiment, concentrated on it’s impact on hydrolyzed amino acids content and fibrosis mass fraction and PPO activity of. The optimum conditions were: 79% high oxygen, 10% alumina, 8% active carbon, 40cm2 exterior proportion of moisture absorption. Under those optimizing conditions, the Agrocybe Chashugu could maintain acceptable commercial value at 1±0．3℃and 95±2 % RH in cold storage for 28 days.6．The pileus ultra-structure and physiological-biochemical indexes of the Agrocybe Chashugu were studied, which were treated by irradiation, low oxygen active modified atmosphere packaging, "high oxygen atmosphere + moisture absorber" packaging. The result showed that with the increased of O2-·and MDA content, the degradation degree of mitochondria and lysosome etc. organelle enhanced, and the activity of cellulase and PPO also heightened, degradation of cell wall and dissolvable protein accelerated, those suggested that the senescence of Agrocybe Chashugu was closely related to the O2-·content. The application of "HOA + moisture absorber" packaging of Agrocybe Chashugu could delay O2-·content increase, delay mitochondria and lysosomc et c. organelle degradation, inhibit PPO and cellulase activity, and maintain the integrality of cell wall, decrease the waste of nutriment.

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