【作者】 程顺昌；

【导师】 纪淑娟；

【作者基本信息】 沈阳农业大学 ， 食品科学， 2013， 博士

【摘要】 南果梨为辽宁省特产水果,成熟时,颜色红艳,皮薄肉细,石细胞少,香气浓郁,在农业部重点区域发展规划(2009-2015年)中,南果梨被列为重点发展的特色梨品种之一。南果梨采收期多集中在9月中上旬,果实采摘后在常温下10-15d果实迅速变软,香气增加,之后迅速软化,果心变褐,严重时果肉也出现褐变,失去特有的商品品质。冷藏虽能较好地保持南果梨品质,但经冷藏后的南果梨出库后在常温货架期间果实果皮和果心褐变问题严重,严重制约了南果梨冷藏技术的推广和应用。褐变已成为影响南果梨产业发展的瓶颈,研究南果梨常温褐变和冷藏后褐变发生机理,为调控南果梨采后褐变的方法与手段提供理论依据,促进南果梨产业的发展具有重要的理论和现实意义。本文以南果梨为试材,分别从果实组织内能量代谢特性和膜脂代谢两个方面研究南果梨常温褐变和冷藏后货架期间褐变发生的内在机理；研究了采后1-MCP, SA和充C02处理对南果梨常温和冷藏后褐变发生的影响,为调控南果梨采后常温褐变和冷藏后褐变提供重要依据。研究结果表明：1)常温下南果梨褐变发生与果实生长期间平均光照时间(R2=0.9058)、有效积温(R2=0.6876)及果实贮藏过程中可溶性固形物含量(R2=0.7524)均高度相关,褐变度与果实生长期(采收期)间极显著正相关,相关系数为94.71%,高于其他因素的的相关系数；随着采收期的延迟,晚采的果实(采收期3)中可溶性固形物含量和乙烯释放量均显著(P<0.05)高于早采果实中的,其含量分别为早采果实的1.27倍和2.2倍。南果梨冷藏后货架期间褐变发生程度与果实硬度呈现高度负相关,相关度92.54%。2)南果梨常温条件下主要发生果心褐变。采收期越晚,果实发生果心褐变程度越严重;与早采的果实相比,晚采果实中ATP含量和能荷峰值时间提前7d出现,在贮藏第7d时,采收期3果实中的ATP含量和能荷值极显著(P<0.01)高于其他两个采收期；较晚采收果实的线粒体蛋白和呼吸控制率也显著(P<0.05)高于其他采收期的,说明细胞内线粒体结构和能量生成水平较高；晚采收的果实中磷脂酶活性也较高(采收期3中的磷脂酶为采收期1的1.53倍),加速了膜脂的降解速度,导致在贮藏第5d时,晚采收的果实膜透性和丙二醛含量较早采收的果实分别提高了1.48倍和2.14倍,膜结构和功能的损伤,再加上果心中总酚含量为比果皮和果肉中总酚分别高出12%和60%,因此最先在果心中发生较严重的褐变。3)南果梨冷藏后常温货架期间主要发生果皮和果心的褐变。较晚采收的果实冷藏后整个货架期间果皮、果肉和果心三个部位的褐变指数和褐变度均高于较早采收果实的；晚采的果实在冷藏后常温货架第5d,呼吸控制率和ATP含量分别为早采果实的1.5倍和1.37倍,货架第5d时,各个采收期均出现线粒体蛋白含量峰值,采收期越晚,峰值越高,采收期3的峰值比采收期1的峰值高出20%；较晚采收的果实中糖转化酶SDH和CCO酶活性峰值比早采果实的提前10d,而且峰值较高,促进了糖类物质的利用和分解；采收期3果实中丙二醛含量和细胞膜透性在整个货架期间均高于其他两个采收期的,最先启动衰老进程,在货架第5d时,越晚采收的果实线粒体和微粒体内磷脂酶活性越高,加速了细胞内不饱和脂肪酸的降解速度,进一步加重了细胞膜结构的破坏,促进了褐变的发生。延长冷藏时间极显著地(P<0.01)加重了冷藏后褐变的发生程度。4)1-MCP处理能明显抑制果实常温褐变的发生,1-MCP处理显著(P<0.05)抑制了果实采后呼吸强度和乙烯释放成量,延缓成熟衰老进程,延长南果梨常温贮藏期21d以上；1-MCP处理能保持南果梨贮藏期间较高水平的线粒体蛋白含量(处理较对照高46.5%)和ATP酶活性,维持ATP含量的稳定；贮藏第14d,1-MCP处理后LOX活性降低31%,延缓了膜中不饱和脂肪酸含量的下降速率；充C02处理与1-MCP处理作用相似,但效果不如1-MCP明显,1-MCP和充C02处理常温下第21d时处理果实的褐变度分别为对照果实的19.2%和51.9%,1-MCP和充C02处理可能是通过保持细胞内能量供给的稳定和抑制细胞膜结构的降解而发挥作用的。SA处理对南果梨常温褐变影响不明显。1-MCP和充C02处理也有利于降低冷藏后货架期间南果梨果实褐变的发生程度,但抑制效果不如常温贮藏的抑制效果好。冷藏后货架第15d时1-MCP和充C02处理果实的褐变指数分别为对照果实的69.0%和95.0%,SA处理的褐变指数为对照的80.1%；1-MCP和充C02处理主要是通过抑制南果梨后熟衰老进程,保持果实组织中能量供应水平和抑制膜脂降解而影响冷藏后褐变发生的；SA处理主要通过抑制磷脂酶和LOX酶活性(货架第5d,处理果实中磷脂酶和LOX酶活性分别为对照的70%和85%),从而保持了较高的磷脂含量(较对照高26%)和较低的脯氨酸含量(为对照果实的62%),说明SA处理有可能是通过保持膜脂结构和功能,提高低温适应性,从而抑制冷藏后货架期间褐变的发生程度。更多还原

【Abstract】 Nanguo pear is the local specialty fruit in Liaoning Province due to its red color, thin skin, few stone cells and rich aroma. It is listed as one kind of the special pears with the key development during the major area agriculture development plan of the agriculture department. Its harvest time is almost in early-September or mid-September. It is softened quickly, aroma increased, then become soft quickly, the core browning, even the flesh browning and loss of the peculia commodity quality when it is stored at room temperature for10-15days after harvesting. Although can the cold storage keep the pear quality well, the aroma was lightened and it can not soften properly during the shelf life at room temperature after cold storage. The serious core and flesh browning has greatly hampered the promotion and application of the Nanguo pear cold storage technology, which has become the bottleneck problem of the Nanguo pear industry development. The study of the Nanguo pear browning mechanism after room temperature storage and cold storage can provide a basis for the approaches and methods how to control the Nanguo pear postharvest browning and will be great importance of promoting the development of the characteristic Nanguo pear industry in Liaoning Province.The inside mechanism of the flesh browning after room temperature storage and cold storage was studied in two aspects involved energy and membrane lipid metabolism. The energy and membrane lipid metabolism to clarify the browning mechanism during browning after the room temperature storage and cold storage with the1-MCP, SA and CO2treatment before harvesting, providing a basis for the further evidence of the Nanguo pear browning and the controls of the pear browning after the room temperature storage and the cold storage.1) At the room temperature condition, browning occurrence had a highly correlation with the preharvest average sunshine time (R2=0.9058). effective accumulated temperature (R2=0.6876) during growth period) and the conten of SSC (R2=0.7524)during the storage at room temperature. And the degree of browning occurrence had a Extremely correlation with the growth time (harvest date), the correlation was as high as94.71%. With the harvest delays, the soluble solids content and ethylene production of late harvested fruit (period of harvest3) were significantly higher than early harvest fruit, and its contents were2.2times to1.27times than the early harvested fruit. Browning occurrence at the room temperature condition after cold storage had a high negative correlation with the fruit firmness, and the correlation was as high as92.54%.2) The browning of Nanguo pear occurred mainly in core at the room temperature condition. The later of the fruit harvest date, the higher of fruit maturity degree. Compared with the early harvest fruit, ATP content and energy charge ahead of time7d peak appears in late picking fruit, In the Storage section7d, the ATP content and energy charge values were significantly (P<0.01) higher than the other two harvest period in the3rd harvest period. Mitochondrial proteins and respiratory control ratio was also significantly (P<0.05) higher than other harvesting period in the late harvest fruit. The results shown that mitochondrial structure and energy generating were maintained at a high level. There was also higher Phospholipase activity in late harvested fruits(the activity of late harvest fruit is1.53times than early harvested fruit, so the degradation rate of membrane lipids were accelerated. Result in the membrane permeability and MDA content in late harvest fruits were increased by48%and114%than early harvest fruits). Damage of membrane structure and function and total phenol content of in core were higher than in peel and pulp, respectively,12%and60%. Therefore, there were the first place in the core there browning occurrence.3) The fruits browning occurrence mainly in peel and core during shelf life at room temperature after cold storage. Browning index and browning degree in late harvest fruit were higher than in earlier harvested fruit, regardless of the peel, pulp or core. During the shelf life of5th days after cold storage, Respiratory control ratio and ATP content in late harvest fruit were1.37times to1.5times respectively than in early harvest fruits. At the same days the fruits of all harvest period had a peak of mitochondrial protein content, and the later the harvest, the peak is higher, the peak of3rd harvest period was1.2times, the peak of SDH and CCO (sugar invertase) activity appeared ahead of10d in late harvest fruits than early harvest fruits, and the peak is also higher than early harvested. This promoted carbohydrate utilization and decomposition. MDA and membrane permeability in the3rd harvest period were higher than other two harvest harvest periods during the entire sheld life. Duiring the5tn days of shelf life, the later the harvest, the higher of the phospholipase activity in mitochondria and microsomes. That can accelerated intracellular degradation rate of unsaturated fatty acids and further exacerbating the structural damage of cell membranes. All these result in browning occurrence. Extend the cold storage time very significantly (P<0.01) increased the occurrence degree of browning after cold storage.4)1-MCP treatment could significantly inhibit browning occurs at room temperature, because1-MCP could significantly inhibited postharvest respiration rate and ethylene production, delay ripening and senescence process, and extend the Nanguo pear storage time21d above;1-MCP treatment can contain the higher levels of mitochondrial protein content (higher46.5%than the control treatment) and ATPase activity in order to maintain the stability of ATP content. At the14th days during the storage, LOX activity treated by1-MCP decreased31%in order to delaying the content of unsaturated fatty acids in membrane decreased rate. CO2treatment has the similar effects with1-MCP, but the effect treated by CO2is not as good as1-MCP. At the21th during the storage, the fruit browning degree treated by1-MCP and C02is19.2%and51.9%respectively than control.1-MCP and CO2treatment may be sufficient to keep the cell by means of a stable energy supply and suppressing the degradation of cell structures play a role. SA treatment at room temperature on the Nanguo pear fruit browning effect is not obvious.1-MCP and CO2treatment were also reducing occurrence of browning degree during the Nanguo pear shelf life after cold storage, but the suppressing effect not as good as room storage effect. During the15th days of shelf life, fruit browning index treated by1-MCP and CO2were the69%and95%compared to the control. The browning index treated by SA was80.1%.1-MCP and CO2treatment mainly through inhibition of Nanguo pear ripening and senescence process maintain higher energy supply level and delayed the degradation of membrane lipid. SA treatment mainly through inhibiting phospholipase (at the5th days during the shelf life, phospholipase activity in fruit treated by SA is the70%compared to the control) and LOX enzyme activity, thus maintaining a high phospholipid content (26%higher in fruit treated by SA than the control) and lower proline content (62%of the control fruits), indicating that SA could kept the membrane lipid structure and function, improve low temperature flexibility, thereby inhibiting browning occurrence during the shelf life at room temperature after cold storage.更多还原