O2和CO2配比对气调贮藏梨采后褐变及相关理化因子的影响

以采后'丰水'梨果实为材料,在乐扣气调试验箱中研究了O2和CO2配比对果实褐变率、多酚氧化酶(PPO)和过氧化物酶(POD)活性、丙二醛(MDA)和总酚含量的影响,以探讨适宜减轻梨气藏褐变的气体成份.结果表明:在整个贮藏过程(150 d)中,'丰水'梨果肉未发生褐变.从贮藏60 d开始,气调处理和冷藏对照果实的果皮均出现褐变,气调处理在贮藏120 d之前对果皮褐变的影响不显著,而在贮藏120～150 d内可显著减轻果皮的褐变、抑制果皮PPO和POD活性及降低总酚含量.与冷藏对照相比,气调处理可推迟果心褐变的时间,且(8%～10%)O2+3% CO2处理可完全抑制果心的褐变;气调处理亦可降低果心PPO活性、减少总酚及MDA含量;(8%～10%)O2+1% CO2处理能够显著提高果心的POD活性,而(8%～10%)O2+3% CO2处理对果实POD活性的影响不显著.可见,气调贮藏主要是通过降低'丰水'梨果皮PPO、POD活性及总酚含量来减轻组织的褐变,并以(8%～10%)O2+3% CO2处理对果实褐变因子的控制效果较理想.     

龙眼果实采后失水果皮褐变与活性氧及酚类代谢的关系

研究了(10±1)℃和50%相对湿度贮藏条件下"福眼"龙眼果实果皮褐变与活性氧和酚类代谢的关系.结果表明,采后失水导致龙眼果实果皮褐变,果皮活性氧清除酶SOD、CAT、APX、GR活性和内源抗氧化物质AsA、GSH含量下降,O-2产生速率和MDA含量增加,细胞膜透性迅速增大;PPO和POD活性增加,总酚和类黄酮含量明显下降.据此认为,果皮褐变可能是细胞的活性氧代谢失调,细胞膜结构破坏,使PPO、POD与酚类物质(含类黄酮)接触、酚类物质氧化的结果.     

钙处理对红富士苹果酶促褐变的影响

渗钙处理能够明显保持红富士苹果的硬度,且褐变度明显低于对照,渗钙对酶促褐变的抑制作用是通过影响PPO活性和LOX活性起作用的,果实褐变的早期发动与LOX活性相关密切,后期褐变则主要是PPO起作用。     

枇杷果皮响应高温强光胁迫的蛋白质组分析

为探讨枇杷[Eriobotrya japonica(Thunb.)Lindl.]果皮在高温强光胁迫下的蛋白质组分变化,采用蛋白质组学方法分析了果实日灼抗性差的枇杷种质‘WDYDB’果皮蛋白质对高温强光胁迫的应答反应。结果表明,在自然高温强光胁迫与遮光处理(对照)下,枇杷果皮蛋白质双向电泳图谱中表达量差异在2倍以上的蛋白点共有31个;通过MALDI-TOF-TOF/MS质谱分析成功鉴定出26个差异蛋白点,包括11个下调蛋白和15个上调蛋白。根据这些蛋白功能,可将其分为防御应答、碳水化合物和能量代谢、光合作用、其它等4类蛋白。同时,对这些蛋白质在高温强光胁迫下的功能和作用进行了讨论。这些差异蛋白质参与了枇杷对高温强光胁迫的响应。     

梨果实采后果心褐变与细胞膜结构变化的关系

作为采后贮藏中经常发生的一种生理病害——梨果心褐变,与细胞膜结构的变化、酚类底物和多酚氧化酶（PPO）的分布、PPO的存在形式和活性有关。细胞膜结构变化或遭受玻坏时,PPO与底物易接触。PPO主要以游离态形式存在且活性高,可导致严重的果心褐变。诱发果心竭变的主要因素冷害、果实缺钙和高二氧化碳伤害都与细胞膜结构的稳定性密切相关。     

苹果日烧病程中果皮抗氧化系统在细胞超微结构的变化

以富士品种为试材研究了苹果果实日烧病程中果皮组织细胞膜脂过氧化、抗氧化酶类、酚类物质的变化规律,并用电镜观察细胞超微结构的变化。结果表明膜脂过氧化导致日烧发生并进一步使日烧程度加重。相应地,抗氧化酶类在果皮变白期活性激增,但是,细胞结构仍较完整,只是叶绿体膨胀、类囊体结构部分解体,线粒体周缘模糊,细胞质中含大量的空泡;以后果皮变褐,绿原酸、槲皮素、芦丁、杨梅酮积累,同时靠近上表皮几层细胞解体,由密集的电子致密物充塞,细胞壁加厚。     

苹果日烧病程中果皮抗氧化系统与细胞超微结构的变化

以富士品种为试材研究了苹果果实日烧病程中果皮组织细胞膜脂过氧化、抗氧化酶类、酚类物质的变化规律,并用电镜观察细胞超微结构的变化.结果表明膜脂过氧化导致日烧发生并进一步使日烧程度加重.相应地,抗氧化酶类在果皮变白期活性激增,但是,细胞结构仍较完整,只是叶绿体膨胀、类囊体结构部分解体,线粒体周缘模糊,细胞质中含大量的空泡;以后果皮变褐,绿原酸、槲皮素、芦丁、杨梅酮积累,同时靠近上表皮几层细胞解体,由密集的电子致密物充塞,细胞壁加厚.     

奉节脐橙果实苯丙氨酸解氨酶活性及其基因表达与果皮褐变的关系

柑橘果皮褐变严重影响果实的商品价值和耐贮性．以奉节脐橙（Citrus sinensis Osbcck）果实为材料,通过采后常温、涂蜡、低温、机械损伤等处理研究了果实果皮褐变率、苯丙氨酸解氨酶（PAL）活性及PAL上基因在果皮褐变过程中表达水平的变化。结果表明,涂蜡、损伤处理均极显著地提高果实的果皮褐变率,而低温贮藏可显著降低其发生率;贮藏期问各处理的PAL活性均呈上升趋势,损伤处理PAL活性显著高于对照。果实发生褐变或受到机械损伤后,PAL2、PAL6基因的表达均比对照明显增强。结果首次表明脐橙果实PAL活性变化以及PAL2基因的表达与果皮褐变具有非常密切的关系．     

壳聚糖涂膜对机械伤苹果抗性生理特征的影响

为了提高苹果采后抗机械损伤能力,减少贮藏损失,以红富士苹果为材料,通过人工模拟机械伤试验,研究壳聚糖涂膜对损伤红富士苹果常温贮藏条件下果肉褐变、相关酶活性及抗性相关物质的影响,探索壳聚糖涂膜在果蔬防腐保鲜上的应用。结果显示:壳聚糖涂膜处理科显著减少红富士苹果果实机械伤口的扩张,提高机械伤果实的总酚含量,降低PPO活性,从而有效抑制机械伤苹果贮藏期间的果肉褐变的发生。同时,壳聚糖涂膜处理可提高机械伤苹果的POD和PAL活性,延缓酚类物质含量的下降,促进体内木质素的合成。研究表明,壳聚糖涂膜处理能够有效防止机械伤苹果贮藏期间的酶促褐变,减少果肉组织中有害物质的积累,促进愈伤组织的形成,从而增强了机械伤苹果的抗性,有效延缓了果实衰老。     

温度对采后石榴果实品质和某些生理指标的影响

研究不同温度对采后石榴品种‘净皮甜’果实品质和某些生理指标影响的结果表明：在5℃条件下贮藏的石榴,其果实中可溶性固形物含量、总糖含量和可滴定酸含量可以得到保持,果皮的相对电导率和褐变指数升高速率减慢,果实的呼吸速率和腐烂率下降,抗坏血酸氧化酶（AAO）和多酚氧化酶（PPO）活性受到抑制,过氧化物酶（POD）和过氧化氢酶（CAT）活性保持相对较高水平。贮藏120d的果实品质良好,保鲜效果也较好。     

Response of the physiological parameters of mango fruit (transpiration,water relations and antioxidant system) to its light and temperature environment

Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperature and intense light conditions that may lead to metabolic and physiological disorders and affect yield and quality. The present study aimed to determine how mango fruit adapted its functioning in terms of fruit water relations, epicarp characteristics and the antioxidant defence system in peel, to environmental conditions. The effect of contrasted temperature and light conditions was evaluated under natural solar radiation and temperature by comparing well-exposed and shaded fruit at three stages of fruit development. The sun-exposed and shaded peels of the two sides of the well-exposed fruit were also compared.     

臭氧水对荔枝采后若干生理生化指标的影响

用不同浓度臭氧水对荔枝果实进行采后处理,测定其花色素苷、类黄酮、可滴定酸和糖含量以及多酚氧化酶和过氧化物酶活性。结果显示,处理后荔枝果皮中花色素苷、类黄酮含量下降速度低于对照,PPO活性低于对照,POD活性高于对照,而果汁中可滴定酸及糖含量与对照相比无显著变化。表明一定浓度臭氧水对荔枝果实保色护色有一定效果,并有防褐变作用。     

Primary and secondary metabolism in the sun‐exposed peel and the shaded peel of apple fruit

The metabolism of carbohydrates, organic acids, amino acids and phenolics was compared between the sun‐exposed peel and the shaded peel of apple fruit. Contents of sorbitol and glucose were higher in the sun‐exposed peel, whereas those of sucrose and fructose were almost the same in the two peel types. This was related to lower sorbitol dehydrogenase activity and higher activities of sorbitol oxidase, neutral invertase and acid invertase in the sun‐exposed peel. The lower starch content in the sun‐exposed peel was related to lower sucrose synthase activity early in fruit development. Dark respiratory metabolism in the sun‐exposed peel was enhanced by the high peel temperature due to high light exposure. Activities of most enzymes in respiratory metabolism were higher in the sun‐exposed peel, but the concentrations of most organic acids were relatively stable, except pyruvate and oxaloacetate. Due to the different availability of carbon skeletons from dark respiration in the two peel types, amino acids with higher C/N ratios are accumulated in the sun‐exposed peel whereas those with lower C/N ratios are accumulated in the shaded peel. Contents of anthocyanins and flavonols and activities of phenylalanine ammonia‐lyase, UDP‐galactose:flavonoid 3‐O‐glucosyltransferase and several other enzymes were higher in the sun‐exposed peel than in the shaded peel, indicating the entire phenylpropanoid pathway is upregulated in the sun‐exposed peel. Comprehensive analyses of the metabolites and activities of enzymes involved in primary metabolism and secondary metabolism have allowed us to gain a full picture of the metabolic network in the two peel types under natural light exposure.     

Cloning and Expression Analysis of Litchi (Litchi Chinensis Sonn.) Polyphenol Oxidase Gene and Relationship with Postharvest Pericarp Browning

Polyphenol oxidase (PPO) plays a key role in the postharvest pericarp browning of litchi fruit, but its underlying mechanism remains unclear. In this study, we cloned the litchi PPO gene (LcPPO, {"type":"entrez-nucleotide","attrs":{"text":"JF926153","term_id":"350601663","term_text":"JF926153"}}JF926153), and described its expression patterns. The LcPPO cDNA sequence was 2120 bps in length with an open reading frame (ORF) of 1800 bps. The ORF encoded a polypeptide with 599 amino acid residues, sharing high similarities with other plant PPO. The DNA sequence of the ORF contained a 215-bp intron. After carrying out quantitative RT-PCR, we proved that the LcPPO expression was tissue-specific, exhibiting the highest level in the flower and leaf. In the pericarp of newly-harvested litchi fruits, the LcPPO expression level was relatively high compared with developing fruits. Regardless of the litchi cultivar and treatment conditions, the LcPPO expression level and the PPO activity in pericarp of postharvest fruits exhibited the similar variations. When the fruits were stored at room temperature without packaging, all the pericarp browning index, PPO activity and the LcPPO expression level of litchi pericarps were reaching the highest in Nandaowuhe (the most rapid browning cultivar), but the lowest in Ziniangxi (the slowest browning cultivar) within 2 d postharvest. Preserving the fruits of Feizixiao in 0.2-μm plastic bag at room temperature would decrease the rate of pericarp water loss, delay the pericarp browning, and also cause the reduction of the pericarp PPO activity and LcPPO expression level within 3 d postharvest. In addition, postharvest storage of Feizixiao fruit stored at 4°C delayed the pericarp browning while decreasing the pericarp PPO activity and LcPPO expression level within 2 d after harvest. Thus, we concluded that the up-regulation of LcPPO expression in pericarp at early stage of postharvest storage likely enhanced the PPO activity and further accelerated the postharvest pericarp browning of litchi fruit.     

The role of anthocyanin in photoprotection and its relationship with the xanthophyll cycle and the antioxidant system in apple peel depends on the light conditions

The synthesis of anthocyanin, the xanthophyll cycle, the antioxidant system and the production of active oxygen species (AOS) were compared between red and non‐red apple cultivars, in response to either long‐term sunlight exposure (high light intensity) during fruit development, or to exposure of bagged fruits to lower light intensity late in fruit development. During fruit development of red and non‐red apples, the xanthophyll cycle pool size decreased much more in red apple peel late in development. With accumulation of AOS induced by long‐term sunlight exposure, enhancement of the antioxidant system was found. However, this change became significantly lower in red apple than non‐red apple as fruit developed, which might serve to accelerate the anthocyanin synthesis in red apple peel. When, late in fruit development, bagged fruits were exposed to sunlight, the accumulation of AOS was lower in red apple peel than in non‐red peel. This could be due to the higher anthocyanin concentration in the red peels. Meanwhile, compared with that in non‐red cultivar, the xanthophyll cycle and the antioxidant system in red apple peel were protected first but then down‐regulated by its higher anthocyanin concentration during sunlight exposure. In conclusions, red and non‐red apples peel possess different photoprotective mechanisms under high light conditions. The relationship between anthocyanin synthesis and the xanthophyll cycle, and the antioxidant system, depends on the light conditions that fruit undergoes.