【作者】 吴靖娜；

【导师】 王则金； 林启训；

【作者基本信息】 福建农林大学 ， 食品科学， 2008， 硕士

【摘要】 鸡腿菇是一种天然绿色食品,味道独特,营养丰富。目前,主要采用罐藏、腌制和干制来延长供应期,鲜销较少,主要原因是远距离贮运过程中易出现开伞、褐变、自溶和纤维木质化等问题未得到有效解决。本论文在探讨了鸡腿菇的自溶现象的基础上,系统研究了鸡腿菇的PPO动力学特性和最适贮藏保鲜温度,并采用涂膜和MAP 2种保鲜方法对鸡腿菇进行贮藏保鲜以解决贮运过程出现的开伞、褐变及自溶等问题。研究内容及结果如下:1、贮藏过程中鸡腿菇自溶现象试验表明,贮藏过程中的鸡腿菇菌柄显著伸长,顶破外菌幕而开伞,并出现褐色斑块,表面黏滑;随着贮藏时间的延长,斑块面积逐渐增大,颜色加深,并有黑色汁液外溢。接种试验提示,微生物并非是引起菇体自溶的直接起因,而是自溶破坏了菇体的组织结构,汁液外溢引起微生物滋生,加速了菇体腐败。2、鸡腿菇自身衰老对鸡腿菇自溶现象的影响对鸡腿菇在自然衰老过程中的自溶指数及若干生理生化指标进行了测定。结果表明,随着菇体衰老,自溶加剧,表现为自溶指数、细胞质膜透性、MDA、O₂^?含量、C_x活性大幅升高,CP含量呈下降趋势;POD、SOD活性呈现先扬后降的趋势,CAT活性前期保持稳定,后期下降。通过相关性分析表明,菇体自溶与菇体自身衰老密切相关。3、鸡腿菇PPO特性研究采用分光光度法对鸡腿菇PPO的催化特性、最适温度、pH及热稳定性等进行了研究,分析了4种不同抑制剂对PPO活力的影响及不同部位PPO活力的差异。结果表明,PPO最适pH为5.0;最适温度20℃,在沸水浴30s后酶活被钝化;鸡腿菇褐变反应动力学符合米氏方程,米氏常数K_m=0.64mol·L^-1,最大反应速度v_max=0.08U·min^-1。柠檬酸、EDTA-2Na、Vc和NaHSO₃ 4种褐变抑制剂对PPO活力表现出不同的抑制效果,以Vc的抑制作用最强;测定鸡腿菇不同部位的PPO活力表明菌盖PPO活力最强,菇柄部位自上而下酶活性逐渐降低。4、最适贮藏温度研究以鸡腿菇开伞率为指标,探讨贮藏温度与开伞率的关系。结果表明,鸡腿菇开伞率与贮藏温度密切相关,在1～3℃温度条件下贮藏的鸡腿菇开伞率较低;高于3℃下贮藏至7d,菇体开始出现开伞、腐败变质等现象。考虑生产过程可能受到外界因素及贮温波动的影响,以（1±0.3）℃作为鸡腿菇的贮藏温度为宜。5、涂膜对鸡腿菇贮藏品质影响研究采用魔芋葡苷聚糖、琼脂、海藻酸钠和淀粉对鸡腿菇进行涂膜。结果表明,采用涂膜剂涂膜鸡腿菇,有助于抑制PPO活力、纤维木质化进程及防止水分的损失。在涂膜剂黏度相同的条件下,海藻酸钠涂膜的保鲜效果最好,表现为纤维木质化质量分数和PPO活力最低,白度（L值）最高,含水率保持在稳定的水平。但到贮藏后期,鸡腿菇表面水分富集,褐变加剧,影响贮藏效果。6、复合涂膜剂的研究采用正交试验方案,探讨了以海藻酸钠、柠檬酸及甘油复合的涂膜剂对鸡腿菇贮藏品质的影响。结果表明,在（1±0.3）℃、相对湿度（9±2）%条件下,海藻酸钠复合膜涂膜剂的最佳工艺参数为1.0%海藻酸钠,1.0%柠檬酸,1.0%甘油;贮藏12 d后,鸡腿菇仍具有较好的内在品质和外观质量,具有可接受的商品价值。7、鸡腿菇MAP保鲜技术研究采用正交试验方案,探讨了MAP中的O₂、CO₂气体浓度及装料量对鸡腿菇贮藏品质的影响。结果表明:在（1±0.3）℃条件下,MAP贮藏保鲜鸡腿菇的最佳工艺参数为5%O₂,8%CO₂,装料量120 g。具体表现为感官质量评分高、粗纤维含量和PPO活性均保持在较低水平,可有效延长鸡腿菇的贮藏保鲜期和货架寿命。更多还原

【Abstract】 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.更多还原