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。     

不同膜包装中CO_2因素对南果梨保鲜效果的影响

以南果梨为试材,使用不同种类保鲜膜进行包装处理,研究包装中不同浓度二氧化碳对南果梨常温保鲜效果影响.结果表明:微孔膜包装处理对果实保鲜效果较好;PVC保鲜膜包装处理+10%的二氧化碳处理可以有效抑制果实呼吸强度,延缓果实中PPO活性、POD活性的变化,具有显著的防褐保鲜效果.     

高渗CO_2和PE保鲜袋对冷藏及货架期‘砀山酥梨’果实品质的影响

【目的】明确冷藏‘砀山酥梨’适宜的保鲜膜包装。【方法】研究不同保鲜膜包装的‘砀山酥梨’果实在(0±0.5)℃低温条件下冷藏150 d和210 d,常温20℃条件下放置24 h和货架9 d时果实呼吸强度、乙醇质量分数、虎皮病和果心褐变以及贮藏品质的变化规律。【结果】果实贮藏210 d+20℃货架9 d时,CK(裸果)果实呼吸强度和乙醇质量分数高,可溶性固形物(SSC)和硬度低,果皮颜色暗、黄,虎皮严重,风味异常,由于失水导致果皮皱缩,果柄干枯、褐变严重,商品价值降低;与CK相比,PVC薄膜袋虽能抑制果皮转黄,保持果实的硬度和果柄的新鲜程度,降低货架期果实的呼吸强度,但由于冷藏期间PVC袋内CO2体积分数高(2.30%~2.70%),O2体积分数低(17.0%~17.9%),导致果实中乙醇积累,造成货架期虎皮病和果心褐变严重,引起风味劣变;PE薄膜袋扎口包装的果实风味基本正常,贮藏效果稍好于PVC包装;PE薄膜袋掩口和高渗出CO2保鲜袋能保持贮藏和货架期果实较高的硬度和可溶性固形物(SSC)以及较低的乙醇质量分数,而且果实风味和外观颜色正常,无虎皮,果心褐变轻微。【结论】‘砀山酥梨’不宜裸果贮藏。相对于PVC和PE薄膜袋扎口包装来说,PE薄膜袋掩口和高渗出CO2保鲜袋对‘砀山酥梨’长期贮藏、保持货架期果实品质和抑制褐变具有良好的效果。     

套袋处理提高‘妃子笑’荔枝果实耐贮性

  对‘妃子笑’荔枝果实进行采前无纺布套袋处理, 采后置于常温、无任何药剂处理和纸皮包装的条件下, 其耐贮性明显优于无套袋对照, 坏果率较低、果皮失水较慢、pH值相对较低。套袋果实果皮的蛋白质含量增多, 过氧化物酶( POD) 活性降低, 但多酚氧化酶( PPO) 活性无明显不同; 果皮蜡质层较对照厚, 海绵状组织有大型薄壁细胞分布。套袋后的变化有利于增强果皮的保水能力和延迟衰老, 从而推迟失水褐变出现的时间, 延长果实的贮藏寿命。     

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。     

自发性气调包装对‘阳丰’甜柿贮藏期冷害及相关指标的影响

以‘阳丰’甜柿为试材,采用不同厚度聚乙烯(PE)袋密封包装果实,以暴露在空气中的果实为对照,研究自发性气调包装(MAP)对冷藏(1℃)过程中‘阳丰’果实冷害的影响。结果表明:与对照相比,0.03mm和0.05 mm PE袋处理均可以抑制果实硬度下降和乙烯释放速率上升,延缓相对电导率和丙二醛(MDA)含量增加,抑制果肉出汁率下降,还可以降低多酚氧化酶(PPO)和过氧化物酶(POD)活性,缓解果实褐变,降低冷害率和冷害指数,且0.05 mm PE袋处理效果优于0.03 mm PE袋处理;0.08 mm PE袋处理也可以抑制果实硬度下降和乙烯释放速率上升,延缓电导率和丙二醛(MDA)含量增加,维持果肉出汁率,但在贮藏后期部分果实会出现非冷害导致的褐变现象。综上所述,在0.03、0.05、0.08 mm PE袋处理中,0.05 mm PE袋处理对控制‘阳丰’甜柿贮藏期间冷害、维持果实外观的效果最佳。     

自发气调包装秀丰梨的贮藏保鲜效果

以0.03mm厚的聚乙烯(PE)膜保鲜袋包装西洋梨秀丰品种果实,作为薄膜自发气调包装(MAP)处理,在0±1℃条件下贮藏,探讨秀丰梨的保鲜效果。结果表明,自发气调包装贮藏能增加秀丰梨贮藏前期可溶性固形物(TSS)含量;降低贮藏期内可滴定酸(TA)含量;保持贮藏期间较高的果肉硬度;延缓果实后熟,降低果实贮藏期间乙烯的释放速率及丙二醛(MDA)含量的峰值;延缓多酚氧化酶(PPO)活力峰值出现的时间并使多酚氧化酶的活力峰值增大,对维持果皮中酚类物质含量及果实抗氧化活性有一定作用,可使秀丰梨贮期延长15天左右。     

自发气调包装对采后“红富士”苹果果皮色素及其相关酶活性的影响

以"红富士"苹果为试材,在(0±1)℃贮藏条件下,分别采用聚氯乙烯袋(PVC,厚度为0.03mm)包装处理(MAP)和不包装处理(对照),研究MAP对苹果果皮色素花青苷、叶绿素、类胡萝素含量及色泽指标(果皮光泽的明亮度、果皮色泽比)的影响,以及花青苷含量变化与其合成相关酶[苯丙氨酸解氨酶(PAL)、查尔酮异构酶(CHI)、二氢黄酮醇还原酶(DFR)、类黄酮-3-O-葡萄糖基转移酶(UFGT)]及降解相关酶[多酚氧化酶(PPO)、过氧化物酶(POD)]活性的变化。结果表明:与对照相比,MAP抑制贮藏期间叶绿素降解及贮藏前期花青苷的积累,延缓类胡萝素的积累及花青苷的后期降解;延缓果实色泽亮度L*及色泽比a*/b*的下降;贮藏期间花青苷的合成与PAL、UFGT活性变化有关,与CHI、DFR活性变化不相关;贮藏期间花青苷降解相关酶PPO、POD活性都呈现先上升后下降的趋势,MAP抑制果皮PPO活性的升高,MAP明显抑制贮藏前期果皮POD活性的上升及贮藏后期POD活性的下降。在采后贮藏过程中,自发气调包装(MAP)有利于延缓"红富士"苹果果皮底色黄化和红色色素的降解,可较好地保持外观品质。     

鲜切生菜贮藏期间产品品质变化及褐变发生规律

为了研究鲜切生菜贮藏期间品质变化和褐变发生的规律及其内在机理,以新鲜圆生菜为试材,经切分处理,置于4℃下贮藏,观测贮藏期间鲜切生菜外观品质、主要营养成分以及与褐变相关的褐变度,苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)活性变化规律。结果表明:随着贮藏时间的延长,经过切分处理的鲜切生菜的含水量逐步降低,失重率增大,后期腐烂明显;主要营养成分叶绿素、还原型维生素C(VC)、可溶性蛋白质含量均出现不同程度的下降;褐变度呈现上升趋势,组织中的PAL活性和总酚含量先升高后逐步下降;PPO活性在整个贮藏时期内呈现出下降趋势,POD活性在贮藏的后期迅速升高。综合分析认为,切分损伤能够诱使PAL活性提高,并促进酶促褐变底物酚类物质的大量积累,通过PPO和POD协同作用,加剧褐变发生;鲜切生菜随贮藏时间延长,其综合品质下降,建议最佳食用期0~3d,货架期0~8d。     

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。     

MA包装和预贮对黑宝石李冷藏品质及褐变的影响

为探讨改善李贮藏性能的方法,以黑宝石李为试材研究了30μmPVC薄膜包装和8℃预贮对李果实贮藏品质及相关酶活性的影响.结果表明,与不包装(对照)相比,采用薄膜包装后直接冷藏(0℃)能有效抑制李果实软化和可溶性固形物含量(SSC)上升,减缓可滴定酸(TA)含量下降;包装后8 ℃预贮5 d、10 d的处理均降低果肉酚类物质...     

二氧化碳高渗透性膜包装对冬枣贮藏品质的影响

以二氧化碳高渗透性保鲜膜包装采后冬枣,以微孔保鲜膜作对照,研究了不同包装方式对冬枣保鲜袋内氧气和二氧化碳浓度、可溶性固形物(SSC)和维生素C(VC)含量、果肉乙醇和乙醛含量、果肉风味及好果率的影响。结果表明:2种包装袋内二氧化碳浓度相近,均低于0.5%的水平;微孔袋内氧气浓度接近于空气中氧含量,但二氧化碳高渗透性膜包装袋内氧气含量在3%～4%之间。二氧化碳高渗透性膜包装的冬枣可溶性固形物和维生素C含量高于微孔膜包装,但2种包装的冬枣的乙醇和乙醛含量相近。二氧化碳高渗透性膜包装的冬枣的风味和好果率明显高于微孔膜包装。     

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.     

Polyphenoloxidase activity during ripening and chilling stress in ‘Manila’ mangoes

Summary

‘Manila’ mangoes were stored at 6 or 12°C, while a control lot was ripened at 258C. Polyphenoloxidase activity was measured in pulp and peel of mangoes during normal ripening and chilling-stress conditions. Compositional parameters (textural hardness, pH, acidity, and soluble solids) were monitored during ripening and chilling injury (CI) was assessed by visual inspection. PPO activity increased in refrigerated mangoes but fruit stored at 6°C displayed greater activity than those stored at 12°C. Both temperatures produced a peak in enzyme activity at day 16 of storage. Peel browning and acidity correlated with PPO activity (r.=.0.9073 and 0.9818) at 6°C. After the PPO peak was observed at day 16, refrigerated mangoes showed lower enzyme activities; however external browning became more pronounced.     

砀山酥梨不同发育时期套袋对石细胞发育的影响

 以不同发育时期套袋处理的砀山酥梨为试材, 研究了果实石细胞团的密度、大小、含量、几种相关酶的活性变化及果实品质等。结果表明, 套袋后果实可滴定酸含量显著高于对照, 而可溶性固形物、可溶性总糖含量、单果质量及果实内石细胞含量等均低于对照; 果实内石细胞团的分布密度在幼果期较高,随着果实发育膨大密度渐低, 接近成熟前两个月左右趋于稳定, 石细胞团的纵径、横径是随着果实发育先增大后减小, 而后又稍有增大, 果实石细胞含量也是先增加后减少, 在盛花后49 d达到最大值。不同时期套袋的果实内苯丙氨酸解氨酶、过氧化物酶及多酚氧化酶的活性均低于对照, 其活性变化是在果实发育初期较高, 盛花后63～77 d处于低水平, 且缓慢下降, 这与果实内石细胞最终含量成正相关。     

臭氧处理对冬枣果实多酚氧化酶和过氧化物酶活性的影响

以冬枣为试材,研究了不同臭氧浓度处理对冬枣果实多酚氧化酶和过氧化物酶活性的影响。结果表明:臭氧处理能抑制冬枣多酚氧化酶的活性,使过氧化物酶活性保持较高水平,其中以40mg/m3臭氧浓度处理最佳。     

Variations in contents of (−)-epicatechin and activities of phenylalanine ammonialyase and polyphenol oxidase of longan fruit during development

Longan fruit has attracted much attention by consumers over the world due to the unique sweet–sour taste. However, the fruit brown rapidly at ambient temperature during storage, due to enzyme-catalyzed reaction of phenolics. Experiments were conducted to understand the variations in the levels of total phenolics and (−)-epicatechin as a major substrate for polyphenol oxidase (PPO) in pericarp tissue of longan fruit during development. The activities of phenylalanine ammonialyase (PAL) and PPO, involved in the synthesis and oxidation of (−)-epicatechin, respectively, during longan fruit development were also measured. During fruit development, the content of total phenolics decreased rapidly and then increased while the content of (−)-epicatechin tended to decrease. Both PAL and PPO activities decreased rapidly at the early fruit development and increased later but the increase of the former appeared was 10 days earlier than the latter. Thus, the level of (−)-epicatechin depended largely on PAL activity but it could involve the conversion of (−)-epicatechin into other flavonoids. This study could help develop appropriate preharvest treatments to control pericarp browning of harvested longan fruit by understanding the variation in the level of the major browning substrate during development.