Study on the mechanism of preservation and alteration of green color in vegetables

1)西兰花(Brassica oleracea L.var.)意大利)采收后迅速衰老，小花在室温下变黄。因此，这种蔬菜的保质期很短。采用一种简单、经济的乙醇蒸气处理粉末状酒精来抑制青花菜的衰老，并阐明了青花菜保鲜的机理。将西兰花的一些枝条与0、3、6或12g粉末酒精一起储存在一个穿孔的聚乙烯袋中，在20℃的黑暗中保存。结果表明，添加3g粉状酒精的乙醇蒸气处理对延缓青花菜的黄化效果显著。但高浓度的乙醇蒸气与12g的酒精混合，产生异味，使小花变软，颜色变深。结果还表明，贮藏2-3天后，乙烯生成量迅速增加，同时，ACC氧化酶活性增加了…未处理的西兰花中的d较多，但在贮藏过程中用粉末酒精处理的西兰花中没有更多的d。这些结果表明，粉末酒精处理是一种简单而经济的延长青花菜货架期的方法，因为它通过抑制ACC氧化酶活性来抑制乙烯的产生。2)进一步利用透射电子显微镜(TEM)来阐明在较高浓度乙醇蒸气下这些异常现象发生的机理。研究了青花菜花瓣组织在贮藏过程中细胞和叶绿体结构的变化。我们发现，从3g粉末酒精中挥发出的适当浓度的乙醇蒸气处理不会引起青花菜宿存细胞的结构变化，但会延缓叶绿体向有色体的转化。相反，较高浓度的乙醇蒸气会导致‘假’质膜分解、质膜断裂和质体修饰，导致小花产生异味并出现暗绿色。3)红色甜椒是一种成熟的水果，最近在市场上销售。本研究旨在提高青熟期采收的辣椒果实在常温下贮藏的品质。本试验利用扫描电子显微镜和透射电子显微镜对甜椒成熟过程中叶绿体向有色体转化的超微结构变化进行了研究。根据扫描电子显微镜观察，随着成熟进程，基粒和基质类囊体出现解体现象。在成熟发育阶段，大量带有结节的小管占据在叶绿体中，可能来源于类囊体膜。根据同一时期的透射电子显微镜观察，叶绿体的大部分被聚集的小管填充。在完全成熟期，观察到纤毛结构的出现。形态计量学分析表明，随着成熟度的增加，基粒类囊体和基质类囊体与叶绿体的比例降低，单类囊体、小泡、油滴、管状结构和纤维结构的比例增加。形态计量学分析结果证实了成熟过程中亚细胞器的数量变化。较少

1) Broccoli (Brassica oleracea L.var. Italicd) senesces rapidly and the florets turn yellow at room temperature after harvest. As a result, this vegetable has a short shelf life. A simple and cost-effective ethanol vapor treatment with powdery alcohol was conducted to inhibit the senescence in harvested broccoli and to clarify the mechanism involved in the preservation of the green color in stored broccoli florets. Some branchlets of the broccoli were stored in a perforated polyethylene bag together with 0, 3, 6, or 12 g powdery alcohol at 20℃ in the dark. Results showed that ethanol vapor treatment with 3 g powdery alcohol was very effective in delaying the yellowing of broccoli florets. However, higher concentration of ethanol vapor with 12 g powdery alcohol produced off-odor and softened the florets, and darkened the green color of florets. Results also indicated that ethylene production increased rapidly after 2 to 3 days in storage and simultaneously, ACC oxidase activity increase … More d in untreated broccoli florets but not in broccoli samples treated with powdery alcohol during storage. These results revealed that powdery alcohol treatment was simple and cost-effective method for prolonging the shelf life of broccoli since it suppresses ethylene production by inhibiting ACC oxidase activity.2) Further study was conducted using transmission electron microscope (TEM) to elucidate the mechanism involved in the occurrence of these anomalous phenomena with higher concentration of ethanol vapor. The structural changes in the cells and chloroplasts in the sepal tissues of broccoli florets during storage were examined. We found that the treatment with adequate concentration of ethanol vapor evaporated from 3 g powdery alcohol did not induce the structural changes of broccoli sepal cells but retarded the conversion of chloroplasts to chromoplasts. On the contrary, higher concentration of ethanol vapor induced 'false' plasmolysis, plasma membrane breaks and modified plastids, resulting in production of off-odor and the appearance of darkened green color in the florets.3) Red-colored sweet peppers are well-ripened fruit, which have been recently sold in the market. This study was investigated to improve the quality of pepper fruit harvested at mature green stage during storage at room temperature. In this experiment, the ultrastructural changes of plastids were examined to elucidate the transfomation mechanism of chloroplasts to chromoplasts during ripening in sweet peppers by using scanning electron microscope (SEM) and TEM. Based on SEM observation, disorganization of grana and stroma thylakoids appeared as the ripening progresses. At the developed stage of ripening, a large number of tubules with nods occupied in the plastids, which were probably derived from the thylakoid membranes. Based on TEM observation at the same stage, the greater parts of the plastids were filled with aggregated tubules. At fully-ripened stage, the appearances of fibril structures were observed. The morphometrical analysis showed that the ratios of grana thylakoids and stroma thylakoids to plastids decreased with ripening whereas the ratios of single thylakoids, vesicles, oil droplets, tubular structures, and fibril structures increased. The results of morphometrical analysis confirmed the quantitative changes of sub-organelles during ripening. Less