高氧动态气调对双孢蘑菇细胞壁代谢及木质化进程的影响

研究高氧动态气调（high-oxygen dynamic controlled atmosphere,HO-DCA）贮藏过程中双孢蘑菇的几 丁质、纤维素和木质素含量,以及细胞壁代谢和木质素合成相关酶活力的变化规律。结果表明：在贮藏后期, HO-DCA处理组的双孢蘑菇几丁质含量显著高于静态气调组与对照组（P＜0.05）,几丁质酶活力显著低于对照 组（P＜0.05）,说明HO-DCA处理有效抑制了细胞壁中几丁质的降解。HO-DCA处理显著抑制了纤维素酶活力 （P＜0.05）,维持了较高的纤维素含量,保持了较高的组织抗压力。双孢蘑菇在其贮藏后期,菌柄木质素含量 急剧升高,木质化程度不断加深,菌柄木质化程度大于菌盖。4-香豆酸-辅酶A连接酶（4-coumarate: coenzyme A ligase,4CL）和肉桂醇脱氢酶（cinnamyl alcohol dehydrogenase,CAD）活力与木质素含量呈显著正相关, 而苯丙氨酸解氨酶活力与木质素含量相关性不显著。HO-DCA处理组的双孢蘑菇木质素含量显著低于对照组 （P＜0.05）,说明HO-DCA处理通过抑制双孢蘑菇4CL和CAD的活力抑制了木质素的积累,延缓了其木质化进 程。研究明确高氧动态气调对其细胞壁代谢及木质化进程的影响,可为有效控制双孢蘑菇质地劣变提供理论依据。     

γ-氨基丁酸对双孢蘑菇贮藏品质的影响

为了探讨γ-氨基丁酸（γ-aminobutyric acid,GABA）处理对双孢蘑菇贮藏品质的影响,研究了不同浓度 GABA处理不同时间对双孢蘑菇冷藏（4 ℃、相对湿度85%）期间质量损失率、硬度和颜色的影响,确定适宜的 GABA处理条件,同时研究了适宜条件GABA处理对冷藏双孢蘑菇总酚、抗坏血酸含量以及多酚氧化酶（polyphenol oxidase,PPO）、过氧化物酶（peroxidase,POD）、苯丙氨酸解氨酶（phenylalnine ammonialyase,PAL）活 力的影响。结果表明,GABA处理能够降低双孢蘑菇的质量损失率、较好地保持其硬度和颜色;其中5 mmol/L GABA处理5 min的保鲜效果最好,在此条件下,冷藏12 d后双孢蘑菇的质量损失率比对照组低44.76%、硬度和L*值分 别比对照组高28.54%和9.41%。同时适宜条件GABA处理能促进双孢蘑菇总酚和抗坏血酸的积累、降低PPO和POD 的活力以及提高PAL的活力。因此,GABA处理较好地保持了双孢蘑菇的贮藏品质,延长了贮藏时间。     

外源γ-氨基丁酸对双孢蘑菇高CO2保鲜品质及生理生化性质的影响

目的 探究外源γ-氨基丁酸(γ-aminobotyric acid,GABA)对双孢蘑菇高CO_2保鲜品质和生理生化性质的影响。方法 分别用5 mmol/L GABA和0.1 mmol/Lγ-乙烯基-γ-氨基丁酸对双孢蘑菇进行预处理,以蒸馏水处理为对照,在21%O_2+10%CO_2气调、温度4℃及RH85条件下进行贮藏,评定其硬度、颜色、总酚、蛋白质、多酚氧化酶(polyphenol oxidase,PPO)、过氧化物酶(peroxidase,POD)、苯丙氨酸解氨酶(phenylalnine ammonialyase,PAL)、H_2O_2、抗·O_2~-活力、过氧化氢酶(catalase,CAT)等指标。结果 外源GABA处理可以保持高CO_2保鲜条件下的双孢蘑菇的硬度和颜色,维持较高的总酚和蛋白质含量,抑制PPO、POD活性,并提高PAL活性;同时,降低H_2O_2含量,提高抗·O_2~-活力和CAT活性;γ-乙烯基-γ-氨基丁酸处理对双孢蘑菇高CO_2保鲜效果无显著影响。结论 外源GABA处理可以通过延缓衰老提高双孢蘑菇高CO_2保鲜条件下的贮藏品质,这为GABA协同高CO_2保鲜双孢蘑菇提供了理论依据。     

适宜真空充氮热处理减缓鲜切双孢蘑菇细胞壁降解

为减缓鲜切双孢蘑菇细胞壁的降解,达到延长贮藏期的目的,研究了不同真空度(0、-20、-40、-60、-80、-98 k Pa)下充氮热处理对鲜切双孢蘑菇贮藏中的硬度、细胞壁组分(蛋白质、可溶性糖和几丁质)含量、细胞壁水解酶(β-1,3-葡聚糖酶和几丁质酶)活性的影响。结果表明,-40 k Pa真空充氮热处理可有效减缓贮藏期间鲜切双孢蘑菇硬度的下降和细胞壁可溶性蛋白质与可溶性糖含量的降低及几丁质含量的升高。真空充氮热处理可显著提高贮藏期间鲜切双孢蘑菇β-1,3-葡聚糖酶和几丁质酶活性,但其变化与细胞壁中可溶性糖和几丁质含量呈非对应关系。研究结果表明,适宜的真空充氮热处理可有效减缓鲜切双孢蘑菇硬度的下降和细胞壁组分的降解,是一种有效的物理保鲜技术。     

GABA处理对双孢蘑菇活性氧代谢和膜脂过氧化的影响

为探讨γ-氨基丁酸(GABA)处理对双孢蘑菇(Agaricus bisporus)活性氧代谢和膜脂过氧化的影响,采用5 mmol/L GABA浸泡处理双孢蘑菇5 min,然后于4 ℃条件下贮藏12 d,测定双孢蘑菇颜色变化、相对电导率、膜脂过氧化产物丙二醛(MDA)的含量、超氧阴离子生成速率、H₂O₂的含量以及过氧化氢酶(CAT)、超氧化物歧化酶(SOD)等抗氧化酶活性的变化。结果表明,GABA处理能够显著提高抗氧化酶CAT和SOD的活性,降低双孢蘑菇的相对电导率、超氧阴离子产生速率和减少MDA、过氧化氢的积累,延缓细胞膜透性和脂质过氧化进程,进而较好的保持双孢蘑菇的L*值,降低其褐变指数,因此,GABA可以用作双孢蘑菇的护色保鲜剂。     

外源亚精胺处理对香菇木质化及相关酶活力的影响

本实验以香菇为原料,分别用10、15 mg/L和20 mg/L亚精胺溶液进行负压渗透处理,4 ℃贮藏16 d,研究了贮藏过程中硬度和木质素、几丁质、纤维素、总酚含量以及苯丙氨酸解氨酶（phenylalanine ammonia lyase,PAL）、过氧化物酶（peroxidase,POD）活力的变化规律。结果表明：所有处理均不能抑制香菇硬度下降,并均促进了纤维素含量升高;15 mg/L的亚精胺处理能够使贮藏末期几丁质含量不发生明显下降;总酚含量在贮藏过程中先增加后降低;15、20 mg/L的亚精胺处理组能够在4～6 d保持较低的PAL活力;而20 mg/L亚精胺处理在贮藏前期（4～6 d）能抑制POD活力,推迟木质化高峰的到来。     

UV-C辐照处理对高节笋冷藏品质的影响

为研究UV-C辐照处理对采后剥壳后的高节笋的品质、木质化和褐变的控制效果,本文将UV-C 4.0 kJ·m-2强度辐照处理剥壳后的高节笋于(6±1) ℃、85%~90% RH环境下贮藏15 d,分析硬度、呼吸速率、失重率、腐烂率、纤维素和木质素含量以及4-香豆酸辅酶A连接酶(4CL)、过氧化物酶(POD)、肉桂醇脱氢酶(CAD)、苯丙氨酸解氨酶(PAL)和多酚氧化酶(PPO)的活性等指标的变化。结果表明:UV-C处理对抑制高节笋切面的褐变,延缓高节笋的硬度、呼吸速率、失重率、腐烂率、纤维素和木质素含量的上升,抑制4-香豆酸辅酶A连接酶(4CL)、过氧化物酶(POD)、肉桂醇脱氢酶(CAD)、苯丙氨酸解氨酶(PAL)和多酚氧化酶(PPO)的活性均有显著性作用(p<0.05)。研究发现,UV-C辐照处理能够通过降低木质素合成代谢的相关酶活以抑制采后去壳竹笋木质素的累积,从而延缓采后冷藏竹笋的木质化进程,使其保持良好的食用品质。     

6-苄氨基腺嘌呤对蕨菜木质化的影响

为了有效地抑制采后蕨菜木质化,延长蕨菜的货架期。分别比较25mg/L 6-苄氨基腺嘌呤(6-benzyl aminopurine,6-BA)及50mg/L 6-BA浸泡处理蕨菜15min后,在13~15℃、相对湿度80%~85%条件下贮藏9d,用清水浸泡作CK,测定苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)、4-香豆酸辅酶A连接酶(4-CL)、肉桂醇脱氢酶(CAD)、过氧化氢酶(CAT)等酶及丙二醛(MDA)含量、木质素含量、蛋白质含量。结果表明:6-BA处理能明显降低与木质素合成相关酶PAL、POD、4-CL、CAD等活力(p0.05);各处理中木质素含量在贮藏期间均呈上升趋势,蛋白质含量呈下降趋势;在贮藏期间,6-BA处理组中木质素及MDA的含量低于CK组;6-BA处理及CK组蛋白组含量均呈下降趋势,但6-BA处理明显抑制蛋白质含量下降和明显提高CAT酶活力。综上50mg/L 6-BA能较好地抑制采后蕨菜的木质化。     

热处理对采后琯溪蜜柚果实汁胞粒化的影响及其与细胞壁代谢的关系

汁胞粒化是柚类果实采后主要的品质劣变现象。本实验以琯溪蜜柚果实为材料,研究热处理对果实贮藏期间品质的影响,探讨其抑制汁胞粒化的作用和适宜处理条件,并探究该抑制作用与细胞壁中木质素和细胞壁多糖代谢的关系。分别以35、42、49、56 ℃热水对琯溪蜜柚果实进行喷淋处理,根据果实冷藏期内汁胞粒化指数、水分质量分数、可溶性固形物和可滴定酸质量分数变化筛选较优处理温度,并评价该温度处理对果实汁胞木质素质量分数、木质素合成酶活力、细胞壁多糖含量及其降解酶活力的影响。结果表明：与其他处理相比,42 ℃热水处理15 min能够较好地延缓琯溪蜜柚果实贮藏期间汁胞粒化指数升高和水分质量分数降低,维持汁胞可溶性固形物和可滴定酸质量分数;与对照组相比,42 ℃热水处理抑制了汁胞中苯丙氨酸解氨酶、肉桂醇脱氢酶和过氧化物酶活性,减缓了木质素质量分数增加;并且抑制了纤维素酶、果胶甲酯酶、多聚半乳糖醛酸酶和β-半乳糖苷酶的活性,延缓了纤维素和半纤维素含量的升高、共价结合态果胶含量降低、离子结合态果胶和水溶性果胶含量的增加。因此,42 ℃热水喷淋处理可有效延缓采后琯溪蜜柚果实汁胞粒化等品质劣变现象,其减缓汁胞粒化的作用可能与木质素合成相关酶和细胞壁多糖降解酶活性受抑制,延缓汁胞木质化、纤维化和果胶降解,使细胞壁组分和结构得到较好的维持有关。     

鲜切雷竹笋冷藏过程中木质化机理的研究

研究鲜切雷竹笋在4℃冷藏条件下苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和多酚氧化酶(PPO)活力及丙二醛(MDA)、多酚、木质素含量的变化规律,探讨其木质化机理。结果显示：在冷藏过程中,PAL、POD活力、MDA含量呈先上升,后下降的趋势;PPO活力在前6d缓慢上升,第15天开始下降;多酚含量在冷藏前6d急剧下降,后缓慢上升,第12天又开始下降;木质素含量不断增加,基部为5%～26%,中部为3%～24%,尖部为2%～22%。结果表明：在冷藏期内,PAL、POD活力大幅度增加,是导致鲜切雷竹笋木质化的关键酶;酚类物质作为木质素合成的前体物质,参与木质素的合成;MDA可能参与鲜切雷竹笋的木质化进程,但需进一步验证;木质素含量从基部向尖部逐渐降低,木质化进程是从基部向尖部推进的。     

纳米包装材料对双孢菇细胞壁代谢及品质的影响

在包装材料中添加纳米银、纳米二氧化钛、纳米凹凸棒土和纳米二氧化硅,制备了一种纳米聚乙烯（polyethylene,PE）包装袋,通过实验来探讨纳米包装材料对双孢菇在贮藏期间的细胞壁代谢和相关酶活性的影响及其保鲜机理。在（4±0.5）℃、相对湿度（90±5）%贮藏条件下测定包装袋内CO2含量、双孢菇的硬度、褐变度、总酚含量、木质素含量、纤维素含量、几丁质含量、苯丙氨酸解氨酶（PAL）和过氧化物酶（POD）活性指标的变化。结果显示,与普通PE包装材料相比,添加纳米粒子的包装材料能够较好地保持双孢菇的质地,抑制子实体的自溶、木质化劣变的现象。贮藏10 d后,纳米包装袋内CO2含量、双孢菇褐变度、纤维素、木质素含量分别比普通PE包装低10.5%、32.2%、15.2%和22.2%,达到显著性差异（P＜0.05）。纳米PE包装袋能够有效地抑制贮藏期间双孢菇木质素的积累、组织纤维化及相关酶活性的上升,较好地保持了双孢菇贮藏品质,延长了贮藏时间。     

Effect of heat treatment on lignification of postharvest bamboo shoots (Phyllostachys praecox f. prevernalis.)

In order to evaluate the effects of heat treatment on the quality of postharvest bamboo shoots, the firmness, disease incidence, respiration and ethylene production, ACC synthase (ACS) and ACC oxidase (ACO) activities, lignin and cellulose contents, and the activities of phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) were examined during storage at 20 °C after heat treatment at 45 °C for 5 h. Heat treatment inhibited disease incidence and respiration, retarded ethylene production, and decreased ACS and ACO activities in bamboo shoots. Furthermore, heat treatment significantly delayed the rise in the activities of PAL, CAD and POD, which were associated with the inhibition of the synthesis of lignin and the delayed tissue lignification. These findings suggest that heat treatment could be a potential tool to delay lignification and decrease disease incidence in bamboo shoots during storage at 20 °C.     

Use of 1‐methylcyclopropene for alleviating chilling injury and lignification of bamboo shoot (Phyllostachys praecox f. prevernalis) during cold storage

BACKGROUND: Bamboo shoot is sensitive to chilling, and low‐temperature injury is a major limitation to its long‐term storage. Studies on the causes of postharvest deterioration in bamboo shoot are few. The aim of the present study was to evaluate the effects of ethylene and 1‐methylcyclopropene (1‐MCP) treatments on the physiological and biochemical responses of bamboo shoot and their ability as a postharvest tool to alleviate chilling injury and lignification of bamboo shoot during storage at 2 °C. RESULTS: Disease incidence, electrical conductivity (EC), respiration and ethylene production of control bamboo shoot increased after about 2–3 weeks of cold storage, associated with higher chilling injury (CI) index. Increased shoot firmness during cold storage was positively correlated with higher lignin and cellulose accumulation, and this accumulation of lignin in flesh tissue was also positively correlated with the activities of phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD). Ethylene treatment was associated with higher disease incidence, CI index, EC, respiration and ethylene production, enhanced lignin and cellulose accumulation and accelerated the activities of PAL, CAD and POD. In contrast, 1‐MCP treatment was associated with lower respiration, ethylene production, CI index and EC, reduced lignin and cellulose accumulation and retarded the activities of PAL, CAD and POD. CONCLUSION: The present findings throw light on the role of ethylene in postharvest physiological disorders such as chilling injury and lignification and suggest that 1‐MCP could be used commercially to control these disorders in bamboo shoot during cold storage. Copyright © 2007 Society of Chemical Industry     

Accumulation of lignin and involvement of enzymes in bamboo shoot during storage

Fresh bamboo (Phyllostachys praecox f. prevernalis.) shoots were harvested, and the changes of firmness, electrical conductivity (EC), respiration rate, ethylene production, total sugars (TS), reducing sugars (RS), lignin and cellulose content and the activity of phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase POD were investigated during storage at 2 or 20°C for 30 or 12 days, respectively. EC increased quickly, with a more rapid rate at higher temperature, but it increased sharply after 24 days at 2°C. Respiration rate increased slowly at 20°C, while at low temperature (2°C) respiration rate and ethylene production significantly decreased. There was a quickly decrease in TS content at 20°C. Shoot firmness, lignin and cellulose increased and accelerated by higher storage temperature during storage at 2 or 20°C. Shoots firmness showed a positive correlation with accumulation of lignin and cellulose in the flesh. Among the enzymes associated with lignin synthesis, PAL and CAD activity showed a persistent rise over the whole 12 days, while POD activity increased rapidly within 6 days during storage at 20°C, followed by a slowly decrease. Accumulation of lignin in flesh tissue was also positively correlated to activity of PAL, CAD and POD. Our results suggest that the increase in firmness of bamboo shoots during storage is a consequence of tissue lignification, a process associated with increases in PAL, CAD and POD activity.     

热激处理对冷藏“解放钟”枇杷果实木质化及相关酶活性的影响

以福建莆田市“解放钟”枇杷为材料,采后50℃热处理30min 后分为冷库(2～5℃)和室温(18～25℃)两种贮藏条件进行贮藏。在贮藏期通过对枇杷果实的木质素含量、硬度、多酚氧化酶(PPO) 、苯丙氨酸解氨酶(PAL)、肉桂醇脱氢酶(CAD)、过氧化物酶(POD)活性变化的分析,研究贮前热处理对冷藏枇杷果实木质化及相关酶活性的影响。结果表明：低温(2～5℃)条件下贮藏,枇杷果实硬度和苯丙氨酸解氨酶活性都有明显升高,且两者呈正相关,相关系数r=0.914。贮前热处理能够延缓冷藏枇杷果实木质素含量及硬度的上升,降低PPO、PAL、CAD、POD 的活性。     

采前苯丙噻重氮喷洒抑制采后双孢菇的软化

目的：研究采前苯丙噻重氮（benzothiadiazole,BTH）喷洒对采后低温贮藏期间双孢菇软化的影响并探讨相关机理。方法：用200 mg/L BTH在原基期（双孢菇菌盖为针头大小时）对‘A15’双孢菇进行喷洒（以自来水喷洒作对照）,测定低温（4 ℃）贮藏期间双孢菇的质地、质量损失率,并分析几丁质、纤维素、总蛋白含量及相关酶活力。结果：与对照相比,采前BTH喷洒能显著降低冷藏期间双孢菇的质量损失率（第8天时比对照组低34.22%）（P＜0.05）;显著提高采收时以及冷藏期间双孢菇的硬度、弹性、咀嚼性和胶着性（P＜0.05）;显著降低采收时和冷藏期间双孢菇的几丁质酶和纤维素酶活力（P＜0.05）,显著提高几丁质和纤维素含量（P＜0.05）;显著降低采收时和冷藏期间双孢菇的中性、碱性和酸性蛋白酶活力（P＜0.05）,延缓蛋白质的降解。相关性分析表明,双孢菇硬度、弹性、咀嚼性、胶着性与几丁质、纤维素、总蛋白含量呈极显著正相关（P＜0.01）,与质量损失率呈极显著负相关（P＜0.01）。结论：采前BTH喷洒可显著延缓双孢菇冷藏期间的软化,其作用机制与抑制双孢菇细胞壁降解酶的活性、减少采后质量损失率密切相关。