不同气体配比对丰水梨采后贮藏期间褐变相关理化因子的研究

以丰水梨为试材,经过5组不同的气体配比处理,分析低温(0±0.5)℃条件下贮藏过程中果实呼吸速率、乙烯释放量、相对电导率、丙二醛(MDA)含量、果心褐变指数、多酚氧化酶(PPO)活性、过氧化物酶(POD)活性的变化。结果表明:丰水梨是呼吸跃变型果实,适宜的气体配比可以降低果实褐变指数的上升,推迟果实PPO、POD活性高峰的出现时间,抑制酚类物质降解,减少MDA生成量,延缓果实褐变发生时间,其中以5%O2+1%CO2处理组果实抑制褐变效果最好。果皮中的酚类物质含量和PPO活性最高,其次是果心,最后是果肉,而POD活性依次为:果皮果肉果心,但整个贮藏过程中,果皮与果肉均没有发生褐变。     

不同浓度水杨酸处理对采后鸭梨果实贮藏过程中褐变的影响

以不套袋鸭梨为研究对象,采用不同浓度水杨酸处理,以水浸果实为对照,对鸭梨采后褐变指数、多酚氧化酶、酚类物质以及保护酶的活性进行测定。以有效地抑制采后鸭梨果实的黑心病,调控鸭梨果实成熟衰老的进程、改善果实品质和贮藏性能提供理论依据。结果表明:0.002、0.020、0.200mmol水杨酸处理鸭梨果实后有效减轻了腐烂和褐变的发生,其中0.200mmol水杨酸处理能显著抑制鸭梨果心中PPO活性和酚类物质的合成,并且对鸭梨果心中SOD、POD保护酶的活性促进效果最显著;而0.002mmol水杨酸处理对鸭梨果心中MDA的含量有显著抑制作用。表明水杨酸处理可以延缓果实衰老,明显抑制鸭梨果心褐变的发生,有利于延长果实的贮藏期。     

黄金梨CA贮藏中果心褐变与相关理化因子的关系

文章研究了不同气体成分对黄金梨果心褐变指数的影响,分析了果心酚类物质、丙二醛(MDA)含量以及多酚氧化酶(PPO)、过氧化物酶(POD)、过氧化氢酶(CAT)活性与果心褐变的关系。结果表明,MDA含量、PPO活性与果心褐变指数呈正相关性,CAT活性与果心褐变指数呈负相关性。较高CO_2和O_2条件促进了果心酚类物质、MDA含量以及PPO活性升高和POD、CAT活性下降,果心褐变发生较早、程度较重。本试验在较低CO_2(1%)和O_2(5%)条件下可使黄金梨贮藏180d以上。     

梨果实酚类物质与酶促褐变底物的研究

 对我国分属不同栽培系统及种间杂交种的10个梨品种果实酚类物质含量进行了系统比较研究。结果表明：高相液相色谱法可检测到梨果中10种酚类物质,不同系统及品种的果实中酚类物质含量差异很大,其中绿原酸平均含量最高,香草醛、芦丁、表儿茶素、儿茶素含量较高,为主要的酚类物质;咖啡酸平均含量最低。对总多酚、绿原酸、表儿茶素、儿茶素、抗氧化活性与褐变的灰色关联分析表明：梨果实总多酚含量对褐变度影响最大,绿原酸含量对褐变度影响其次,果实抗氧化活性对褐变的影响最小。不同酚类物质中绿原酸含量最高,且与多酚氧化酶结合能力最强,为最主要的褐变底物。     

李低温酶促褐变机理的研究

以美国紫李为试材,测定了经间歇升温和热处理后果实的褐变度、抗氧化酶活性、抗氧化剂含量、膜质过氧化水平、总酚和可滴定酸含量的变化规律。结果表明:热处理和间歇升温延缓了李果褐变的发生,维持体内高水平的抗氧化活性和总酚以及可滴定酸含量,抑制多酚氧化酶(PPO)、过氧化物酶(POD)的活性和膜质过氧化产物—丙二醛(MDA)含量的积累。同时发现,对照果实POD活性与总酚含量和褐变度密切相关(r=-0.9157和0.9782)。说明对照果实在冷藏过程中由于内源清除活性氧能力的减弱,使膜质过氧化作用加剧,从而造成细胞膜系统结构和功能的改变,细胞中区域化分布被打破,酚类底物与POD、PPO接触,最终导致果实组织褐变。     

砂梨果肉褐变与酚类物质及相关酶活性的相关分析

【目的】为了探明砂梨褐变的内在机制,为砂梨贮藏与加工过程中品种选择和褐变控制提供理论依据,【方法】以11个砂梨品种的成熟果实为试材,测定总酚与酚类物质组成及含量、GSH含量、PPO、SOD、CAT、PAL、POD酶活性等相关指标。【结果】结果表明,不同品种酶促褐变程度有很大差别,‘新兴’和‘早生黄金’褐变较重,而‘秋黄’和‘丰水’较轻。绿原酸、儿茶素、芦丁和没食子酸是梨果肉中含量较高的酚类物质。总酚含量与果实褐变度相关性最高,绿原酸次之,儿茶素最低。【结论】梨果肉褐变相关酶活性与酚类物质组分及含量对其酶促褐变的影响程度因品种不同而存在差异。梨果肉酶促褐变与总酚和绿原酸含量的相关度高于与酶类的相关度。     

采后桃果实酶促褐变机理的研究进展

桃是典型的呼吸跃变型果实,成熟于高温盛夏季节且采收后后熟迅速,一般采后5～7d就开始出现果肉褐变的现象,严重降低了果实的品质和经济价值。国内外对果实酶促褐变机理进行了广泛的研究,果实褐变现象主要是由多酚氧化酶(PPO)作用于天然底物酚类物质所导致的。通过文献分析,理清采后桃果实褐变的研究范畴和热点,本研究主要从采后酶促褐变机理、褐变底物、贮藏期间酚类底物含量的变化及延缓采后桃果实褐变的措施等方面进行了综述;发现采后桃果实褐变底物的化学结构鉴定研究缺乏系统的研究,今后仍需加强有关采后桃果肉酶促褐变底物种类及其化学结构鉴定、贮藏褐变期间酚类底物含量的变化趋势等方面的研究,为完善采后桃果实的酶促褐变机理提供理论依据。     

白及原球茎褐变过程中总酚及相关酶活性的变化

以不同褐变程度的白及原球茎为试材,研究了白及原球茎褐变度与总酚含量、多酚氧化酶(PPO)、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)活性的关系.结果表明:在一定褐变度范围内,随褐变程度的增加,总酚含量升高,超过一定范围,总酚含量随褐变程度增加而降低;PPO与PAL活性变化趋势一致,在褐变前期与褐变度呈正相关,后期活性随褐变度增加而降低;POD活性随褐变度增加而略有降低.     

采后赞皇大枣不同包装处理的生理生化性状差异

利用PVC穴50μm厚雪、PE-G(绿色,20μm厚)、PE-W(白色,20μm厚)3种保鲜膜包装赞皇大枣,与对照(不包装)相比,在0℃贮藏条件下,包装处理能较好地保持果实的风味,降低果肉褐变度、可溶性总糖、酚和丙二醛(MDA)含量及过氧化物酶(POD)的活性。除贮藏前期PVC和PE-W包装的果实具有较高的多酚氧化酶(PPO)活性外,其余时期各包装处理果实中PPO活性低于对照。贮藏前期不同处理间可溶性蛋白质含量差异较小,后期PE-G和PE-W处理的果实中具有较高的可溶性蛋白质含量。总体看来,3种保鲜膜相比,以PE-G包装处理抑制褐变和保鲜效果最好。     

‘金川雪梨’采后黑心病发生机理研究

为进一步明确‘金川雪梨’采后货架期间果实褐变过程中内在品质和相关生理代谢途径变化规律,补充完善‘金川雪梨’黑心病发生机理和调控途径,以同期采收黄皮果实和绿皮果实为试材,于室温(20±0.5)℃下,调查测定货架0 d和10 d果实组织褐变指数,系统分析比较二者主要品质指标、生理代谢等变化的差异。结果表明:黄皮果实货架0 d和10 d,其果心和果肉组织褐变指数显著高于绿皮果实;货架10 d时,与绿皮果实相比,其可溶性固形物、可滴定酸含量及果实硬度均显著降低;果肉组织乙醇和乙醛含量显著升高;过氧化物酶(POD)、超氧化物歧化酶(SOD)及过氧化氢酶(CAT)等主要抗氧化酶活性降低;丙二醛含量升高,可溶性蛋白含量降低,细胞相对电导率显著升高;多酚氧化酶(PPO)活性相对较高,总酚含量下降;货架期间黄皮果实呼吸强度和乙烯释放速率均显著高于绿皮果实。因此,‘金川雪梨’黄皮果实采后乙烯和呼吸代谢旺盛,加速了果实衰老,果实乙醇、乙醛等发酵代谢产物积累,抗氧化酶活性降低,膜质过氧化水平加重,PPO催化酚类底物氧化,进而导致‘金川雪梨’果实黑心等组织褐变发生。     

1-MCP、薄膜包装和乙烯吸收剂对‘安哥诺’李长期冷藏期间品质和褐变的影响

果肉软化和褐变是李果实长期冷藏时的主要问题。以‘安哥诺’李为材料,采用1-MCP(0.5μL.L-1)、薄膜(30μm厚)包装(MAP)及包装内加入乙烯吸收剂(EA)的方法,研究了0℃冷藏期间‘安哥诺’李品质、褐变及其生理生化的变化。结果表明,与对照(未进行处理)相比,1-MCP、MAP和MAP+EA及其组合处理延缓了果肉软化,抑制可溶性固形物(SSC)和花青苷含量上升,保持果肉较高的白度指数,降低果肉褐变度、酚含量和多酚氧化酶(PPO)活性,1-MCP+MAP+EA的复合处理效果最佳。这些说明,采后进行1-MCP、MAP和EA的复合处理能有效抑制果肉软化和褐变,改善了果实贮藏品质。     

低温贮藏对‘金红’苹果能量代谢和品质的影响

为探究不同贮藏温度对‘金红’苹果果实能量代谢和生理品质的影响，将‘金红’苹果分别放置在–2、0、2、4 ℃条件下贮藏，定期测定果实能量相关物质三磷酸腺苷（ATP）、二磷酸腺苷（ADP）、磷酸腺苷（AMP）含量和能荷（EC）变化以及H+-ATPase、Ca2+-ATPase、琥珀酸脱氢酶（SDH）、细胞色素氧化酶（CCO）、超氧化物歧化酶（SOD）等相关酶活性，同时测定果实呼吸速率、乙烯释放速率、果实硬度、维生素C、可滴定酸、可溶性固形物含量等生理品质指标，并调查果实组织褐变情况。结果表明：整个贮藏及货架期，–2 ℃下的果实ATP、ADP和AXP（AXP = ATP + ADP + AMP）含量、EC以及能量相关代谢酶活性（H+-ATPase、SDH、CCO）、SOD、乙烯释放速率始终保持最低，维生素C含量后期下降迅速；4 ℃下的果实硬度、可溶性固形物含量和可滴定酸含量降幅较大；–2 ℃下的果实褐变指数最高（果皮和果肉均出现了严重褐变），0 ℃下的果实果皮和果肉也有轻微褐变，2 ℃和4 ℃果实无褐变。贮藏30、45、90 d以及贮藏90 d + 货架3 d和90 d + 货架5 d期间，2 ℃贮藏的果实保持较高的能量水平，果实品质和风味保持较好，0 ℃果实次之。研究结果表明，‘金红’苹果组织褐变与能量亏缺有密切关系，能量亏缺越多，褐变越严重，适宜的低温能维持果实较高的能量水平，同时抑制果实褐变，维持果实较好的贮藏品质，延缓果实衰老。     

Effects of nitric oxide fumigation on post-harvest core browning in ‘Yali’ pear (Pyrus bretschneideri Rehd.) during cold storage

Summary

Core browning often occurs as a physiological disorder in ‘Yali’ pear (Pyrus bretschneideri Rehd.) and results in a high losses during storage. In this study, the effects of fumigation with nitric oxide (NO) gas on the incidence of core browning in ‘Yali’ pears during cold storage were investigated. ‘Yali’ pear fruit were treated with 0, 10, 20, or 30 µl l^–1 NO at 25º ± 2ºC for 3 h under anaerobic conditions, then stored at 0º ± 1ºC under normal air for up to 120 d. The data showed that fumigation with 20 µl l^–1 NO was most effective at suppressing core browning. Thereafter, treatment with 20 µl l^–1 NO was used for comparisons with untreated control fruit in experiments to measure changes in total phenolics contents, polyphenol oxidase (PPO) activities, and the contents of glutathione (GSH), ascorbic acid (AsA), and NO in fruit core tissue during storage. The results showed that NO-fumigated fruit had lower PPO activity, but higher GSH and AsA contents in their core tissue compared with untreated control fruit. NO fumigation also maintained higher endogenous NO levels in core tissue after 60 d in storage, while the total phenolics contents of fruit remained at lower levels until day-100 of storage. These results indicate that the inhibitory effect of fumigation with

20 µl l^–1 NO on core browning was associated with its effects on reducing PPO activity and total phenolics contents, while maintaining the contents of GSH and AsA in core tissue of ‘Yali’ pear during cold storage.     

Variations in contents of browning substrates and activities of some related enzymes during litchi fruit development

Pericarp browning is a major factor to limit storage and transportation of postharvest litchi fruit. Experiments were conducted firstly to determine variations in contents of browning substrate (−)-epicatechin in pericarp tissues of litchi fruit during development. Changes in the activities of polyphenoloxidase (PPO), peroxidase (POD) and phenylalanine ammonialyase (PAL) in association with the synthesis or oxidation of (−)-epicatechin were also examined. (−)-Epicatechin content tended to decrease during fruit development. PAL activity had a high level at the initial stage of fruit development, then decreased rapidly, and finally increased slightly, which was in agreement with the variation in (−)-epicatechin content. The higher contents of total phenolics and (−)-epicatechin of fruit of ‘Nuomici’ than ‘Feizixiao’ were also related to the higher PAL activity. PPO had a similar change to PAL in activity, but POD activity slowly decreased at the early fruit development and then increased markedly. It is suggested that (−)-epicatechin content might be largely regulated by PAL activity. This study could help to understand the variations in the content of the browning substrate and the activities of some substrate-related enzymes of litchi fruit during development and then control better pericarp browning of harvested litchi fruit by the application of appropriate preharvest treatments.     

采后浸钙对雪花梨果肉褐变的影响

雪花梨果实采后常压浸泡６％ＣａＣｌ２１５分钟或减压浸泡４％ＣａＣｌ２２分钟能保持果肉较高水平的酚类物质（酚类物质与果肉钙含量呈显著正相关，ｒ＝０．８６３７），抑制ＦＰＰＯ（游离态多酚氧化酶）活性，维持细胞膜结构的完整性（果肉相对电导率与果肉钙含量呈显著负相关，ｒ＝－０．８７７５）。雪花梨果肉褐变与果肉钙含量及氮钙比有关，含钙量愈低或氮钙比愈高，果肉愈易褐变。重病果与健康果相比，其果肉钙含量低４４．６％，氮钙比高７５．３％。     

Effects of polyethylene bags,ethylene absorbent and 1-methylcyclopropene on the storage of Japanese pears

Summary

Storage of the ‘Nijisseiki’ cultivar of Japanese pears was studied over three seasons for periods up to 36 weeks at 0°C. Storage in 50 μm thick low-density polyethylene (LDPE) bags at 0°C considerably delayed yellowing in all experiments, even after fruit was removed to 20°C for 1 week at the end of storage. The addition of an ethylene absorbent made from potassium permanganate on aluminium oxide (Purafil II) further delayed yellowing. Carbon dioxide levels in both treatments varied, but were generally in the range 2–3%. Oxygen levels remained high, generally 16–19%. In bags without Purafil, ethylene levels rose slightly during storage and were generally about 0.15 μl l^–1. When Purafil was included in the bags, the ethylene level was reduced 10-fold or more. A sensory test indicated that the use of LDPE bags and ethylene absorbent resulted in fruit with better eating quality than fruit stored in air. Disorders over the 3-year investigation were low even after long-term storage. The use of polyethylene bags reduced the severity of flesh browning, and flesh spot decay was virtually absent. The use of bags increased the severity of core browning. Inclusion of an ethylene absorbent in bags reduced the severity of disorders, particularly core browning. Treatment of the fruit with 1-methylcyclopropene (1-MCP), before or during storage, resulted in higher ethylene levels in the polyethylene bags. At the concentrations used, 1-MCP did not improve the storage of ‘Nijisseiki’ compared to the use of polyethylene bags with Purafil II.     

不同温度和CO_2体积分数对丰水梨采后生理指标的影响

为明确丰水梨采后适宜的贮藏温度和CO2体积分数,从果实硬度、膜透性、乙醇质量分数、总酚质量分数、PG活性、PPO活性及果心褐变等方面研究了不同温度和CO2体积分数对丰水梨果实的防褐保鲜效果。结果表明,-1.5℃明显降低果实腐烂率,维持较高的果实硬度,但果实发生不同程度冷害;5℃适合短期贮藏(<60d)。与CK相比,3%O2+1%CO2可较好保持果实硬度和风味,明显抑制PPO活性、乙醇产生和果心褐变,延缓酚类物质降解,较好保持细胞膜完整性;2%CO2防褐保鲜效果次之;3%～5%CO2防褐保鲜效果最差。     

套袋黄冠梨黑点病与钙素营养和果实衰老的关系

为探明套袋黄冠梨果实黑点病发病原因,从采后生理、矿质营养水平、酚类物质酶促褐变和果实衰老等方面对套袋黄冠梨果实黑点病进行了研究。结果表明:套袋果呼吸强度显著高于不套袋果;套袋果Ca含量仅为不套袋果的49%-63%,果皮钙素含量未套袋果>套袋健康果>套袋病果,套袋病果与不套袋果果皮N/Ca比值分别为9.8和6.1,K/Ca比值分别为17.6和8.8;果皮和果心酚类物质含量及多酚氧化酶活性(PPO)呈套袋病果>套袋健康果>未套袋果的趋势;套袋病果果皮丙二醛(MDA)含量及电导率显著高于未套袋果;果皮钙素含量与其PPO活性、多酚及丙二醛含量、电导率呈高度负相关。初步分析黄冠梨果实黑点病病因为缺钙性生理衰老。     

草酸处理减轻杧果采后果实冷害的机理研究

 杧果（Mangifera indica L.）‘Zill’果实采后经5 mmol · L^-1草酸溶液浸泡10 min后,在低温（10± 0.5）℃下贮藏27 d,再移至常温25℃贮藏4 d,冷害系数和质膜相对透性显著低于对照;草酸处理降低了果实在贮藏后期的呼吸速率和乙烯释放速率,抑制了多酚氧化酶（PPO）和过氧化物酶（POD）活性,维持了较高果肉亮度值（L^*）,可溶性固形物（SSC）、游离脯氨酸和柠檬酸含量。说明草酸处理可提高质膜稳定性,抑制褐变相关酶活性以及维持一些渗透调节物质含量来增加采后果实的抗冷性,缓解果实冷害症状。     

苹果新品种‘苹帅’

‘苹帅’苹果是以‘向阳红’ב胜利’杂交育成的中晚熟优良品种。果形端正,大小整齐,平均单果质量203.2g,果形指数0.84;果实浓红色,光洁靓丽,蜡质明显;果肉黄白色或浅黄色,质细,硬脆,多汁,香气浓,甜酸适口;采后硬度8.7kg·cm-2,可溶固形物14.6%,品质优;果实易着色,适宜无袋栽培;树体和果实抗轮纹病,耐瘠薄,适应性强。