Improving storability,physiological disorders,and antioxidant properties of ‘Bartlett’ and ‘d’Anjou’ pears (Pyrus communis L.) by pre-harvest 1-methylcyclopropene spraying

Ethylene continues to be a major factor influencing quality of European pears during storage. Although research has been done on the effect of pre-harvest 1-methylcyclopropene (1-MCP) on physiological characteristics in pears, a full understanding of cultivar response and antioxidant metabolism remains elusive. Spraying 1-MCP on ‘Bartlett’ and ‘d’Anjou’ pears was studied with respect to physiology, storage and eating quality, disorders, and antioxidant properties at two harvest date (H1 and H2) during storage and ripening. Treatment with 1-MCP extended the harvest window of ‘Bartlett’ and ‘d’Anjou’ pears 3 and 4 days, respectively, without reducing storage or eating quality. Treatment with 1-MCP reduced ethylene production (EPR) and respiration rates (RR), maintained fruit firmness and green colour during storage and retarded development of desirable melting texture in both cultivars. Additionally, 1-MCP lowered the incidence of disorders by alleviating membrane lipid peroxidation, retaining high total flavonoids (TF) and antioxidant capacity, and enhancing superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activity in both cultivars. Overall, pre-harvest 1-MCP applications could extend storage time of ‘Bartlett’ and ‘d’Anjou’ pears to 5 and 6 months, respectively, at −1.1 ± 0.5 °C, by reducing ethylene synthesis and enhancing antioxidant metabolism.     

1-MCP处理对库尔勒香梨贮藏品质和生理效应的影响初报

试验以库尔勒香梨为试材,研究0.10 mg/kg,0.20 mg/kg,0.30 mg/kg浓度1-MCP对香梨贮藏过程中果实品质和生理变化的影响。结果表明:1-MCP结合保鲜袋和冷藏处理能够明显抑制果实质量损失,保持果实硬度,防止果实内总酸含量、可溶性固形物含量、维生素C含量变化。其中,0.10 mg/kg 1-MCP结合MAP和冷藏处理能较好地保持细胞膜的完整性,抑制维生素C含量变化,防止褐变;0.20mg/kg 1-MCP结合保鲜袋和冷藏处理能较好地保持果实质量。但1-MCP处理不能很好地控制保鲜袋内CO2的释放量,抑制微环境中果实的呼吸强度。     

不同贮藏条件对库尔勒香梨果实采后生理及贮藏效果的研究

在不同的贮藏条件下,每隔15d对库尔勒香梨果实各生理指标进行测定,分析库尔勒香梨果实在贮藏过程中生理变化规律,及库尔勒香梨果实黑心病、化学锈斑(又称果皮病)、果皮发黄、干耗的原因。通过对贮藏效果的测定,确定最佳贮藏参数和加湿方法。     

Cloning and some properties of Japanese pear (Pyrus pyrifolia) polyphenol oxidase,and changes in browning potential during fruit maturation

A PCR‐amplified genomic DNA fragment encoding Japanese pear (Pyrus pyrifolia) polyphenol oxidase (PPO) was cloned and sequenced. The DNA appears to encode a 66 kDa precursor protein consisting of a 56 kDa mature protein and a 9.5 kDa N‐terminal transit peptide. The amino acid sequence showed high homology with apple PPO. The PPO mainly existed as a soluble fraction in cells and was limitedly proteolysed, while the mature form (56 kDa) was detected in plastids. Immature fruits showing high browning potential had high PPO activity and a high level of phenolics, while mature fruits showing little browning had high PPO activity but a low level of phenolics. Copyright © 2003 Society of Chemical Industry     

Loss of ascorbic acid during storage of Conference pears in relation to the appearance of brown heart

To investigate the causes of brown heart (BH) in Conference pears, the contents of ascorbic acid (AA) and dehydroascorbic acid (DHAA) in fruits were studied during the first period of storage. AA was studied in 1999 and 2000, DHAA in 1999 only. Pears from normal and very late harvest stored immediately or after a delay in a controlled atmosphere with 2% O₂ and low (0.7%) or high (5%) CO₂ were compared. DHAA content did not change during storage in any treatment. AA decreased in storage according to an exponential model. The rate of AA loss was different in the two years and was higher in late‐harvest fruits and in those stored in 5% CO₂. BH appeared in different treatments when AA decreased below a threshold, which was about 2 mg kg^?1 fresh weight, corresponding to 5% of the AA content at harvest. The frequency and severity of symptoms depended linearly on the time spent by fruits in low‐ascorbate conditions. Advanced maturity at harvest and storage in high CO₂ determine the appearance of BH and increase the rate of AA loss, probably through a reduction in the turnover of antioxidants. © 2002 Society of Chemical Industry     

Chemical Composition of Seed Oils Recovered from Different Pear (Pyrus communis L.) Cultivars

Lipophilic bioactive compounds in oils recovered from the seeds of eight pear (Pyrus communis L.) cultivars were studied. Oil yield in pear seeds ranged between 16.3 and 31.5 % (w/w) dw. The main fatty acids were palmitic acid (6.13–8.52 %), oleic acid (27.39–38.17 %) and linoleic acid (50.73–63.78 %), all three representing 96–99 % of the total detected fatty acids. The range of total tocochromanols was between 120.5 and 216.1 mg/100 g of oil. Independent of the cultivar, the γ‐tocopherol was the main tocochromanol and constituted approximately 88 %. The contents of the carotenoids and squalene were between 0.69–2.99 and 25.5–40.8 mg/100 g of oil, respectively. The β‐sitosterol constituted 83.4–87.6 % of total sterols contents, which ranged between 276.4 and 600.1 mg/100 g of oil. Three significant correlations were found between oil yield and total contents of sterols (r = ?0.893), tocochromanols (r = ?0.955) and carotenoids (r = ?0.685) in pear seed oils.     

南果梨果心挥发性成分的分析

用同时蒸馏萃取装置(SDE)提取南果梨果心挥发性成分，测得南果梨果心中挥发性成分的含量为0．25％，用GC／MS法从南果梨果心挥发性成分中分离并确认出50种化学成分，用峰面积归一法通过G1710BA化学站数据处理系统得出各化学成分在挥发性成分中的百分含量，其中主要成分为依兰烯(29．78％)，2，6一二甲基-6-(4-甲基-3-丙烯基)双环[3．1．1]庚-2-烯(9．53％)，1-甲基-4-(5-甲基-1-甲烯基-4-己基)环己烯(6．43％)等，占总检出量的80．66％。     

‘香水梨’和‘嘉宝梨’后熟期间呼吸强度及品质指标的变化及其比较

以商业成熟的‘香水梨’和‘嘉宝梨’为试材,经室温(20±3)℃、相对湿度85%~90%条件下后熟,测定后熟期间的生理和品质指标的变化。结果表明,‘香水梨’后熟期间的呼吸强度呈典型的跃变型变化,显著高于‘嘉宝梨’,且‘香水梨’在第5天出现呼吸高峰,‘嘉宝梨’虽在第15天时有呼吸高峰出现,但变化不显著;‘嘉宝梨’的可溶性固形物含量和固酸比显著高于‘香水梨’,两者的可溶性固形物含量分别在第15天和第10天时达到最大,‘香水梨’可滴定酸含量显著高于‘嘉宝梨’,后熟期间均逐渐下降;果实色泽变化为a*值变化最明显,‘香水梨’显著高于‘嘉宝梨’,后熟期间均逐渐上升;2种梨后熟期间石细胞含量基本不变,硬度逐渐减小,质量损失率逐渐增大,均为‘香水梨’高于‘嘉宝梨’。综上所述,‘香水梨’和‘嘉宝梨’均属于跃变型果实,后熟期间果实色泽和质地等品质性状均显著提升。     

砂梨品种果实冷藏期间质地及品质差异性评价

目的:确定砂梨品质形成及劣变关键点。方法:以早生新水、沪晶梨18、沪晶梨67为试材,将成熟度一致的3个品种的梨果实于(1.0±0.5)℃、相对湿度85%～90%的冷库中贮藏60 d,每10 d测定果实品质和10个电子鼻传感器的感应值。结果:沪晶梨18和早生新水为典型的果糖积累型,沪晶梨67为山梨醇积累型,3个品种梨均为苹果酸积累型。冷藏期间,沪晶梨67可保持较高的果实带皮硬度、果肉组织硬度、脆性和咀嚼性;含有较高的葡萄糖、山梨醇和总糖含量,可滴定酸、苹果酸含量较稳定;贮藏风味浓郁,受冷藏时间调控小,耐贮性佳。沪晶梨18的果皮特性、紧实度和脆性优于早生新水,拥有较高的果糖、苹果酸含量和果糖/总糖,可保持较高的甜酸度,贮藏风味浓郁。早生新水易软化,可滴定酸含量呈急剧下降趋势,综合风味受贮藏时间调控大,不耐贮。早生新水和沪晶梨67梨果实挥发性化合物发生了明显变化,特别是氮氧化合物、甲烷、硫化物、乙醇等挥发性化合物。结论:早生新水、沪晶梨18、沪晶梨67的安全冷藏期分别为30,40,60 d。     

苹果梨和鸭梨酶促褐变机理的研究

以苹果梨和鸭梨为研究对象。在一定的贮藏期内,通过定期测定梨中ｐＨ值,可溶性固形物,褐变度,总酚和多酚氧化酶活性及其与不同底物的结合能力,分析梨的酶褐变机是,苹果梨和鸭梨在贮藏期间,ｐＨ值和可溶性固形物的含量总体呈下降趋势;多酚类物质的含量和多酚氧化酶的活性呈上升趋势,与贮藏期间的褐变度的升高是一致的,多酚氧化酶与底物结合能力的强弱依次为：没食子酸〉儿茶酚〉绿原酸〉咖啡酸;抗坏血酸和还原糖含量对水果