【作者】 郜海燕；

【导师】 郑永华；

【作者基本信息】 南京农业大学 ， 食品科学， 2008， 博士

【摘要】 枇杷和水蜜桃是浙江省重要特色水果,近年种植增长较快,成为农业增效、农民致富的重要途径,在全省新农村建设中发挥了积极作用。但枇杷和水蜜桃果实含水量高,皮薄质软易伤,且在高温高湿季节上市,极易腐烂；低温贮藏又易发生冷害,造成木质化和软褐,保鲜难度大,当前又缺乏有效实用的贮运保鲜技术,严重制约了产业的持续发展。鉴于此,我们研究了不同枇杷品种的冷害发生、低温耐贮性和抗冷害贮藏保鲜技术以及不同成熟度水蜜桃的冷害发生、低温耐贮性和抗冷害贮藏保鲜技术,主要结果如下：1.不同枇杷品种果实的低温耐贮特性和品质变化存在较大差异：红肉类品种‘大红袍’、‘夹脚’和‘大叶杨墩’枇杷果实在0～1℃下贮藏过程中硬度上升较快、出汁率降低明显、木质素积累较多,冷害症状明显；相比而言,白肉类品种‘白沙’枇杷硬度增加和出汁率下降要小得多,木质素的积累也最少,冷害症状较轻；红肉类枇杷果实冷害的发生与木质化合成酶PPO、POD和PAL活性的增加密切相关；‘白沙’枇杷虽在0～1℃下不易产生冷害,但贮藏50天(d)后,果实腐烂率高,可溶性固形物、总酸和维生素C含量下降快,贮藏效果差；‘大红袍’枇杷腐烂轻,但随着贮藏期的延长,果实冷害症状明显,同时酸度下降,糖酸比失调,也不宜长久贮藏；‘大叶杨墩’枇杷在贮藏50 d后,糖酸比较为适宜,口感好,同时冷害症状也较轻,耐贮性好。2. N2预处理、减压贮藏和MAP等保鲜新技术可较好的抑制枇杷果实冷害的发生,具体为：(1)N2处理8小时(h)抑制了枇杷0～1℃下的呼吸强度和乙烯产生速率,抑制了果实可溶性固形物、总酸和维生素C含量下降的幅度。同时与未经N2处理的果实相比,N2处理后POD和PAL活性在整个贮藏期间增加缓慢,表明N2处理减轻枇杷果实的冷害与组织的POD和PAL活性的增加和木质化合成有关。(2)减压贮藏抑制枇杷果实呼吸强度和乙烯产生速率,降低果肉硬度增加幅度,减轻腐烂,明显抑制可溶性固形物和维生素C含量的下降,抑制了枇杷果实整个贮藏过程中POD和PAL等木质素合成关键酶活性增加幅度,降低了木质素含量的增加,减轻了枇杷果实冷害的程度,保持果实较好的品质和质地。(3)MAP可维持冷藏枇杷相对稳定的O2和CO2的气体浓度,有效地降低枇杷果实的呼吸速率和乙烯释放速度,延缓维生素C和总酸的消耗,减少硬度的增加,降低腐烂率,抑制木质化相关酶活性,减少木质素的增加,减轻冷藏枇杷木质化。3. 7～8和9成熟2种不同采收成熟度的‘湖景蜜露’水蜜桃低温贮藏效果差异较大：7～8成熟的水蜜桃在(1±1)℃条件下腐烂率较轻,但表现出硬度增加,质地发脆,出汁率下降等冷害现象,可溶性固形物、总酸和维生素C含量也出现明显的下降；褐变指数不断增加；9成熟的水蜜桃贮藏期间果实硬度下降缓慢,出汁率平稳增加,褐变程度较轻,可溶性固形物、总酸和维生素C含量较高,乙烯释放量和呼吸强度保持较高水平,呼吸高峰较平稳,同时果实的品质和风味较好,商品价值较高,比7～8成熟的水蜜桃果实具有较好的抗冷性。因此,南方软质水蜜桃低温贮藏时应以9成熟采收为宜。4. NO、减压处理、MAP结合1-MCP处理可提高水蜜桃冷藏效果。具体为：(1)NO处理维持了水蜜桃较高的糖酸比,抑制了果实维生素C含量和硬度的下降,保持了水蜜桃较好的风味,抑制了果实的呼吸强度和乙烯产生速率,降低了相对电导率的增加幅度,抑制了MDA含量的积累,相对保持了细胞膜的完整性,降低了贮藏期间PPO和POD活性的上升趋势,抑制果实褐变,具有较好的贮藏保鲜效果。(2)减压贮藏可明显延长水蜜桃的贮藏时间,降低呼吸强度,能较好地保持果实的品质、硬度和水分。水蜜桃贮藏较佳的减压压力是50～60 kPa。(3)MAP结合1-MCP保鲜技术处理降低了水蜜桃果实低温贮藏期间呼吸强度和乙烯产生速率,并推迟呼吸峰的出现时间,显著抑制了水蜜桃果实硬度、可溶性固形物和总酸含量的下降；同时,降低了PE、PL和PG等细胞壁降解酶的活性的增加幅度,抑制了PPO和POD活性的增加,减轻了果实的褐变,保持水蜜桃中SOD和CAT较高的活性,减少组织内自由基的积累,延缓水蜜桃果实的衰老进程。更多还原

【Abstract】 Loquat (Eriobotrya japonica Lindl.) and peach(Prunus persica (L) Batsch) are characteristic fruit of Zhejiang province. The loquat fruit ripen in early summer, and when ripe, are spherical or oval in shape, orange yellow or white in color, with a thin, tough skin, and soft, juicy flesh. Loquat and peach fruit are famous for their good taste and nutritive value. The harvest season of these fruit is usually hot and rainy, and hence unfavorable for storage and transportation. Because of this, large postharvest losses can occur. In view of this, it is important and necessary to conduct in-depth studies on the mechanism of chilling injury and anti-chilling injury technology of the loquat and peach fruit.There were big differences in the low temperature storability and quality of different varieties of loquat fruits. Red loquat cultivas, included "Dahongpao", "Jiajiao" and "Dayayangdun", showed fruit firmness increased steadily, and fresh juice percentage decreased. The changes of fruit firmness and fresh juice percentage were the characteristics of tissue lignification. In contrast, white loquat cultiva, "Baisha", was not in obvious chilling injury during storage. The chilling injury of red loquat cultivas was closely related to the increase of the activities of PPO, POD and PAL. Although the"Baisha" loquat not had a chilling injury in the 0～1℃, it showed high decay rate and TSS, TS and Vc content decreased rapidly after 50 d storage. Loquats (Dahongpao) had the best storage qualities among varieties and decay rate had reached 8.2%after 50 days storage. However, they were easy to be harmed by chilling injury. Loquats (Dayayangdun) showed moderate ration of sugars to acids, rich flavor, good taste, and with no apparent lignification phenomenon.There were big differences in the low temperature storability and quality of different varieties of loquat fruits. Lower temperature storage, chilling injury occurred with symptoms of lignification, tissue browning, and a decrease in percentage juice, percent soluble solids, titratable acidity and vitamin C, increase in electric conductivity, lignin content and lignification enzyme activities.Short-term N2 pretreatment, hypobaric storage and MAP could inhabit occurring of the chilling injury of the loquat.The loquat fruits with 8h N2 pretreatment were effective in delaying senescence. Short-term N2 treatment could maintain higher level of total soluble solid and titratable acidity, reduce decay incidence and increases in activities of SOD and CAT increasing. In contrast, lower levels of membrane permeability, malondialdehyde (MDA) content, superoxide anion generation rate and LOX activities were observed in short-term N2 treatment fruit. During the storage, the higher ability of the enzymatic antioxidant systems was found in the loquat treated with short-term N2 treatment.Hypobaric storage significantly reduced the rates of respiration and ethylene production, delayed the onset of their peak values, inhibited browning index, and maintained high contents of total soluble solids, titratable acidity and vitamin C. Moreover, hypobaric storage inhibited the increase of POD and PAL activities, reduced their peak values, delayed the increases of flesh firmness and lignin content, inhibited the decrease of extractable juice rate, thereby maintaining good eating quality and extending the storage life of cold-stored loquat fruit.MAP were effective in reducing the increase of respiration and ethylene production, firmness, decay rate, lignin content, maintaining high contents of titratable acidity and vitamin C.The storage qualities of peach were much difference between seventy to eighty percent maturity and ninety percent maturity. Compared to fruits of seventy to eighty percent maturity, fruits of ninety percent maturity had strong chilling tolerance and kept good quality during low temperature storage, which showed that there were lower flesh firmness, slight browning index, high juicy rate, contents of soluble solids content, titratible acidity and ascorbic acid and ethylene production rate and respiration rate. This was related to inducing the increase in activities of SOD and POD, reducing accumulation of free radical and alleviating chilling injury for juicy peaches with high maturity grade. Thus, the best harvest maturity grade for juicy peaches storage performed well was ninety percent maturity. Short-term NO pretreatment, hypobaric storage and MAP combined with 1-MCP could improve the storage quality of the peach.The peach fruits with NO pretreatment were effective in extending the shelf-life. Short-term NO treatment could maintain higher ration of sugars to acids, firmness and vitamin C, reduce the increase of respiration and ethylene production, membrane permeability, MDA content. During the storage, the higher ability of the enzymatic antioxidant systems was found in the peach treated with short-term NO treatment.Hypobaric storage significantly extended the shelf-life of the peach. It was found that the storage qualities were varied with different pressures. The appropriate pressure was 50-60 kPa.The peach fruits, which treated by 1-MCP and MAP, could reduce the increase of respiration, delay senescence, keep firmness and maintain percent soluble solid. At the same time, lower levels of activities of PE, PL and PG were observed in MAP combined with 1-MCP treatment fruit. And MAP combined with 1-MCP treatment fruit had higher activities of SOD and CAT, which reduced the accumulation of free radical, slowed down senescence course.更多还原