【作者】 姜红波；

【导师】 王则金； 林启训；

【作者基本信息】 福建农林大学 ， 农产品加工贮藏， 2007， 硕士

【摘要】 茶树菇是一种集营养、保健于一身的纯天然食用菌，味道独具一格。近年来，随着人们消费观念的转变，市场对鲜茶树菇需求量日趋增大。但茶树菇在一般条件下，较难贮藏和运输，主要是由于远距离贮运过程产生的菇色褐变、菌盖开伞、菇体失水和纤维素木质化等问题未得到很好解决。为此，本论文以茶树菇（Agrocybe aegerita）为试验材料，系统研究了茶树菇的PPO动力学特性和最适贮藏保鲜温度。并运用辐照、低O₂AMAP及HOAP等3种物理方法对茶树菇进行贮藏保鲜，通过分析贮藏过程品质效应及细胞超微结构观察，阐明可行性和商业价值，为茶树菇工厂化贮藏保鲜提供理论依据和技术支持。研究内容与结果如下。1、茶树菇PPO动力学特性研究着重探讨了底物浓度、pH值及温度等因素对PPO（多酚氧化酶）活力的影响，建立了相应的酶促褐变反应动力学方程。此外还对茶树菇不同部位的PPO活力进行了研究。结果表明，底物（C₆H₆O₂）浓度较小时反应初速率呈直线上升趋势，浓度较大时，其变化对反应初速率影响较小；茶树菇PPO的最适pH值4.0～5.0，最适温度50℃。引用Michaelis—Menten机理描述得到茶树菇PPO活力的动力学方程，求得反映底物与酶结合的米氏常数K_M=2.59mol／L，最大反应速率νmax=0.127U／min。不同部位的茶树菇PPO活力不同，菌盖的PPO活力最强，菌褶次之，菇柄则自上而下逐渐降低。2、最适贮藏温度研究以茶树菇开伞率为考察指标，分析了贮藏温度与开伞率间的关系。结果表明，茶树菇开伞率与贮藏温度密切相关，在0℃～3℃条件下贮藏的茶树菇开伞率较低；高于3℃下贮藏至5d，菇体开始出现开伞、腐败变质等现象。通过重复实验得出，茶树菇的最适贮藏温度为（1±0.3）℃。3、茶树菇⁶⁰Coγ射线辐照保鲜研究研究了⁶⁰Coγ射线不同辐照剂量对茶树菇贮藏过程的开伞率、PPO活力、MDA含量及体现茶树菇内在品质特征的粗纤维、V_C质量分数和游离氨基酸含量的影响。结果表明，茶树菇采用辐照剂量0.8kGy结合低温（1±0.3）℃贮藏，可有效抑制各种生理代谢活动，延缓衰老进程，并保持较高的V_C质量分数。4、茶树菇低O₂AMAP贮藏保鲜研究采用正交试验方案，探讨了AMAP中的装料量、O₂及CO₂气体浓度对茶树菇贮藏品质的影响。结果表明，在（1±0.3）℃条件下，茶树菇AMAP贮藏保鲜的最佳工艺参数为O₂1％，CO₂8％，装料量150g。具体表现为游离氨基酸含量、粗纤维质量分数和PPO活力的极差分析得出均保持在较低水平，有效延长茶树菇的贮藏保鲜期和货架寿命。5、茶树菇HOAP贮藏保鲜研究考察了不同高O₂浓度对茶树菇品质的影响。试验表明，HOAP中的O₂浓度80％的贮藏效果最好，在低温条件下可有效抑制各种生理代谢活动，延缓其衰老进程。但随贮藏时间的延长，茶树菇表面出现结露水珠现象，后续以游离氨基酸含量、粗纤维质量分数及PPO活力为考察对象，采用4因素4水平的正交试验方案对“HOA+吸湿剂”包装处理进行优化与分析，得出游离氨基酸含量、粗纤维质量分数变化较小及PPO活力较低的较优水平组合为O₂79％，氧化铝用量10％，活性炭用量8％，吸湿表面积40cm²。以此优化因素水平包装茶树菇，在温度（1±0.3）℃、相对湿度（95±2）％条件下贮藏保鲜28d，仍具有可接受的商品价值。6、采后处理对茶树菇子实体衰老的影响机理初析通过对“HOA+吸湿剂”包装、低O₂AMAP和辐照处理的茶树菇贮藏期间细胞超微结构观察和品质变化的分析得出，茶树菇贮藏过程中的O₂^?、MDA含量越高，线粒体及溶酶体等降解程度越严重，纤维素酶、PPO等活性随之升高，细胞壁及可溶性蛋白降解加快，说明O₂^?与茶树菇衰老密切相关。其中“HOA+吸湿剂"包装处理能有效减缓茶树菇O₂^?增加，延缓线粒体及溶酶体等的降解，抑制贮藏过程茶树菇PPO及纤维素酶活力，较好的保持了细胞壁的完整性，减少其营养物质的损耗。更多还原

【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 K_M andυ_max 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.更多还原