陈晨^,, 姜爱丽, 刘程惠, 赵琪琪, 张艳慧, 胡文忠^,大连民族大学生命科学学院/生物技术与资源利用教育部重点实验室,辽宁大连 116600

Effect of UV-C on the Browning of Fresh-Cut Huangguan Pear

CHEN Chen^,, JIANG AiLi, LIU ChengHui, ZHAO QiQi, ZHANG YanHui, HU WenZhong^,Ministry of Education, College of Life Science, Dalian Minzu University/Key Laboratory of Biotechnology and Bioresources Utilization, Dalian 116600, Liaoning

通讯作者: 胡文忠,E-mail： hwz@dlnu.edu.cn

责任编辑: 赵伶俐
收稿日期:2020-05-4接受日期:2020-07-22网络出版日期:2020-12-16

基金资助:

国家重点研发计划.2016YFD0400903 国家自然科学基金.31801598 大连市青年科技之星项目.2017RQ147

Received:2020-05-4Accepted:2020-07-22Online:2020-12-16
作者简介 About authors
陈晨,E-mail： chenchen@dlnu.edu.cn。








摘要
【目的】探索UV-C预处理后鲜切和鲜切后UV-C辐照两种方式对鲜切梨褐变的控制效果及其生理机制,为鲜切梨的贮藏保鲜以及扩大UV-C在果蔬方面的应用提供理论依据。【方法】以鲜切‘皇冠’梨为研究对象,分别在鲜切前、后采用UV-C（有效波长254 nm）辐照处理5 min,分析在5℃贮藏过程中,两种方式UV-C处理后鲜切梨的褐变程度（BI）、多酚氧化酶（PPO）、苯丙氨酸解氨酶（PAL）活性、总酚含量、抗氧化相关酶（超氧化物歧化酶（SOD）、过氧化氢酶CAT、抗坏血酸过氧化酶APX、谷胱甘肽还原酶GR）活性、H₂O₂和丙二醛（MDA）含量以及非酶抗氧化能力（DPPH、ABTS自由基清除能力和还原能力）的变化。【结果】与对照相比,两种UV-C处理均能显著抑制鲜切梨的褐变,其中鲜切后UV-C处理控制效果更好。两种UV-C处理均不同程度提高鲜切梨的PPO活性、降低PAL活性和总酚含量,同时提高鲜切梨的抗氧化酶活性以及非酶抗氧化能力,抑制了H₂O₂和MDA的积累。相关性分析显示,鲜切梨的BI值与CAT、APX和GR活性以及非酶抗氧化能力呈极显著负相关（P<0.01）,与H₂O₂和MDA含量呈极显著正相关（P<0.01）。【结论】UV-C处理主要通过提高鲜切梨的抗氧化防御能力从而延缓贮藏过程中的表面褐变,两种处理方式相比,鲜切后UV-C处理更能有效提高鲜切梨的抗氧化能力,对褐变控制效果更好。
关键词： 鲜切梨;褐变;UV-C;生理机制

Abstract
【Objective】In order to provide an experimental basis for the preservation of fresh-cut pears and enlarging the application of UV-C, the effects of pre-processing and post-processing UV-C treatment on the browning inhibition of fresh-cut pears and its possible physiology mechanism were studied.【Method】Fresh-cut pears were separately treated by pre-processing and post-processing UV-C (254 nm) for 5 min, and then the physiological parameters were evaluated, including browning degree (BI), the activities of polyphenol oxidase (PPO), phenylalnine ammonialyase (PAL), total phenolic content (TPC), H₂O₂ and MDA content, the activities of antioxidant enzymes (superoxide dismutase, SOD, catalase CAT, ascorbate peroxidase APX, glutathione reductase GR) and non-enzymatic antioxidant capacities (DPPH, ABTS radical scavenging activities and reducing power).【Result】The results showed that both pre-processing and post-processing UV-C treatment could effectively delay the browning of fresh-cut pears. Post-processing UV-C treatment exhibited better browning controlling effect than that of pre-processing UV-C treatment. Both two kinds of UV-C treatments could improve the PPO activity, reduce the PAL activity and TPC, as well as increase the enzymatic and non-enzymatic antioxidant activities of fresh-cut pears and decrease the accumulation of H₂O₂ and MDA. Statistical analysis indicated that BI were significantly negatively correlated with CAT, APX and GR activities, and non-enzymatic capacities (P<0.01). While there was a positive correlation between BI and H₂O₂, MDA content (P<0.01).【Conclusion】These findings suggested that UV-C treatment delayed browning of fresh-cut pears during storage mainly through improving the antioxidant defense system. Post-processing UV-C treated fresh-cut pears possessed higher antioxidant activity than that of pre-processing treated samples, therefore, which exhibited better browning controlling effect.
Keywords：fresh-cut pears;browning;UV-C;physiology mechanism


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本文引用格式
陈晨, 姜爱丽, 刘程惠, 赵琪琪, 张艳慧, 胡文忠. UV-C处理对鲜切‘皇冠’梨褐变的影响[J]. 中国农业科学, 2020, 53(24): 5081-5090 doi:10.3864/j.issn.0578-1752.2020.24.011
CHEN Chen, JIANG AiLi, LIU ChengHui, ZHAO QiQi, ZHANG YanHui, HU WenZhong. Effect of UV-C on the Browning of Fresh-Cut Huangguan Pear[J]. Scientia Acricultura Sinica, 2020, 53(24): 5081-5090 doi:10.3864/j.issn.0578-1752.2020.24.011


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0 引言

【研究意义】近年来,鲜切果蔬由于其方便、快捷、卫生、营养等优点,深受国内外消费者喜爱。但鲜切操作,例如去皮、切分等,会引发果蔬发生一系列复杂的生理变化,从而加速果蔬衰老和品质劣变。其中切割伤害引起的表面褐变是包括鲜切梨在内的多种鲜切果蔬品质下降以及货架期缩短的主要因素之一,也是目前鲜切果蔬加工和贮藏过程中面临的重要问题^[1,2]。因此,探索一种有效的保鲜方法来延缓鲜切果蔬在贮藏期间的表面褐变,对延长其货架期具有重要意义。【前人研究进展】鲜切果蔬表面褐变是一个复杂的过程,一般认为鲜切操作破坏了果蔬组织结构,使细胞空间区域化丧失,打破了原来多酚氧化酶（PPO）与其底物酚类物质的分区定位,从而使酶与底物接触,导致酶促褐变反应的发生^[3,4]。近年来的研究表明鲜切操作引起活性氧（ROS）的大量产生,导致膜脂过氧化,从而破坏膜结构,加剧酶促褐变反应。提高抗氧化能力能够有效降低ROS积累,从而减轻膜脂过氧化,降低褐变程度^[5,6,7]。因此,酚酶反应、ROS过量产生、膜脂过氧化、抗氧化系统损伤与鲜切果蔬表面褐变具有重要关系。短波紫外线（UV-C）是一种被认为安全的（GRAS）杀菌技术,目前已允许其应用于多种食品的表面杀菌^[8],适宜计量的UV-C处理还能有效控制多种鲜切果蔬贮藏期间的表面褐变,但褐变控制机理各不相同。例如适宜计量的UV-C可以降低PPO、过氧化物酶（POD）和苯丙氨酸解氨酶（PAL）活性,减轻细胞损伤,从而抑制鲜切莲藕和鲜切杨桃的褐变^[9,10]。HUANG等^[11]研究发现UV-C处理通过降低PPO和POD活性,同时提高PAL活性、总酚含量和抗氧化能力来有效控制鲜切百合的褐变。笔者前期研究发现,UV-C处理也能有效延缓鲜切苹果贮藏期间的褐变,但是并不能抑制其PPO活性^[12],进一步研究认为,UV-C主要是通过提高抗氧化防御系统,调节ROS代谢抑制鲜切苹果褐变^[13]。【本研究切入点】目前UV-C对鲜切果蔬的褐变控制研究均为鲜切后UV-C处理,完整果蔬UV-C预处理后鲜切的研究尚未见报道。同时,针对不同鲜切果蔬产品,UV-C控制其褐变的生理机制也不尽相同。【拟解决的关键问题】本研究以鲜切梨为研究对象,采用UV-C预处理后鲜切以及鲜切后UV-C处理两种方式,动态监控贮藏期间鲜切梨的褐变程度,同时分析与褐变相关生理指标的变化,系统研究两种UV-C处理方式对鲜切梨褐变控制的生理机制,为鲜切梨的贮藏保鲜以及扩大UV-C在果蔬方面的应用提供理论依据。

1 材料与方法

试验于2017年5月至2018年4月在大连民族大学生命科学学院进行。

1.1 材料与试剂

‘皇冠’梨：购于大连经济技术开发区乐购超市,选择大小均一、色泽均匀、无病虫害、无机械损伤、表面光滑的梨果进行试验;过氧化氢、无水乙醇、丙酮、福林酚、愈创木酚、苯丙氨酸、硝普钠、聚乙烯吡咯烷酮、硫代巴比妥酸、三聚乙酸、邻苯二酚等试剂（分析纯）,购于天津市科密欧化学试剂开发中心;GR、SOD试剂盒,购于苏州科铭生物技术有限公司。

1.2 仪器与设备

CR400/CR410型色差计,日本Konica Minolta公司;电子分析天平AL240,瑞士Mettler Toledo公司;电热恒温水浴锅DK-S26、电热恒温鼓风干燥箱DHG- 9053A,上海精宏实验设备有限公司;紫外可见分光光度计UV-9200,北京瑞利分析仪器有限公司;匀浆机T-25,德国IKA;台式高速冷冻离心机BR4i,法国Jouan;制冰机SiM-F140,日本三洋。

1.3 样品预处理

将‘皇冠’梨随机分成3组：第一组‘皇冠’梨置于紫外灯（有效波长为254 nm）下35 cm处照射5 min,随后于5℃冷库贮藏12 h,用灭菌的削皮刀去皮去核切割成约1.5 cm³的小块,为预UV-C处理组;第二组‘皇冠’梨置于5℃冷库贮藏12 h后,按照与第一组相同的操作进行鲜切处理,再采用UV-C辐照处理,为UV-C处理组;第三组‘皇冠’梨置于5℃冷库贮藏12 h后鲜切,作为对照。每组处理量为220块鲜切样品,设置3个重复,将3组处理后的鲜切梨分别放入一次性托盘中并用保鲜膜包好,置于5℃冷库中贮藏。定期取样用于分析生理生化变化。

1.4 生理指标的测定

1.4.1 褐变指数 褐变指数（BI）的测定采用色差计测定L*、a*、b*值,根据公式计算^[14]。

BI=[100(x-0.31)]/0.172

x=(a*+1.75 L*)/(5.645 L*+a*-3.012 b*)

1.4.2 H₂O₂含量测定 H₂O₂含量的测定参考PATTERSON等^[15]的方法。3 g样品加入5 mL丙酮均质,4℃下10 000 r/min离心20 min。取1 mL上清液加入0.1 mL四氯化钛的浓盐酸溶液和0.2 mL浓氨水,混合液10 000 r/min离心15 min,取沉淀溶于3 mL H₂SO₄中,410 nm下测定吸光值,以H₂O₂绘制标准曲线并计算,结果用μmol?g^-1表示。

1.4.3 总酚含量测定 总酚含量（TPC）的测定采用福林酚法^[16]。5 g样品加入25 mL 75%乙醇超声提取40 min,4℃下10 000 r/min离心20 min,上清液用于测定总酚含量和抗氧化活性。取1 mL上清液加入福林酚试剂0.2 mL,快速混匀后加入20% Na₂CO₃溶液1 mL,充分混匀,室温避光放置30 min,在760 nm下测定吸光值,以没食子酸作为标准品绘制标准曲线并计算。样品中的总酚含量用mg/100 g表示。

1.4.4 酶活性测定 PPO、CAT和APX活性测定参考CHEN等^[17]的方法,PAL活性测定参考李雪等^[18]的方法,GR、SOD测定采用试剂盒法。

酶液提取：5 g样品分别加入20 mL不同酶提取液均质后,4℃下12 000 r/min离心30 min,上清液用于酶活性测定。PPO、CAT提取液为0.2 mol?L^-1 pH 6.4 磷酸缓冲液（含1 g聚乙烯吡咯烷酮）;APX提取液为0.1 mol?L^-1 pH 7.5磷酸缓冲液（含1 mmol?L^-1 EDTA和3 mmol?L^-1抗坏血酸）;PAL提取液为0.1 mol?L^-1 pH 8.7的硼酸钠缓冲液（含0.037% EDTA、0.137% β-巯基乙醇、3%聚乙烯吡咯烷酮）,GR和SOD提取液分别来自苏州科铭生物技术有限公司生产的GR和SOD活性测定试剂盒。

PPO活性测定：按顺序依次加入2.4 mL 50 mmol?L^-1乙酸-乙酸钠缓冲液（pH 5.5）、0.6 mL 50 mmol?L^-1 邻苯二酚、0.1 mL酶液,420 nm扫描3 min吸光值变化,以每min下降1个吸光值作为一个酶活性单位（U）。

CAT活性测定：依次加入1.9 mL 0.1 mol?L^-1磷酸缓冲液（pH 7.8）、0.1 mL酶液、0.3 %H₂O₂,240 nm扫描3 min吸光值变化,以每min下降0.01吸光值作为1 U。

APX活性测定：依次加入2.6 mL 50 mol?L^-1磷酸缓冲液（pH 7.5,含0.1 mmol?L^-1 EDTA、0.5 mmol?L^-1 抗坏血酸）、0.1 mL酶液、0.3 mL 2 mmol?L^-1 H₂O₂,290 nm扫描3 min吸光值变化,以每min下降0.01吸光值作为1 U。

PAL活性测定：按顺序依次加入3 mL 50 mmol?L^-1硼酸-硼砂缓冲溶液（pH 8.8）、0.5 mL 20 mmol?L^-1 L-苯丙氨酸溶液、0.5 mL酶液,37℃孵育60 min,分别在孵育前后290 nm测定吸光值,以每h下降0.01吸光值作为1 U。

1.4.5 抗氧化能力 抗氧化能力采用DPPH自由基和ABTS自由基清除能力以及还原能力3种方法进行测定^[19]。

DPPH自由基清除能力测定：0.1 mL多酚提取液加入3.9 mL 0.1 mmol?L^-1 DPPH溶液中,混合后室温静置30 min,于517 nm测定吸光值。

ABTS自由基清除能力测定：2.45 mmol过硫酸钾与等体积7 mmol?L^-1 ABTS混匀后避光放置12—16 h,适当稀释后使其在734 nm下吸光值约为0.7,即为ABTS工作液,将0.1 mL样品加入3.9 mL ABTS工作液中,反应5 min后在734 nm测定吸光值。

还原能力测定：将300 mmol?L^-1乙酸缓冲液（pH 3.6）、40 mmol?L^-1 TPTZ溶液（用10 mmol?L^-1 HCl配制）和20 mmol?L^-1 FeCl₃溶液以10﹕1﹕1的比例混合制得FRAP工作液。待测样品提取物与FRAP工作液以1﹕30（v﹕v）的比例混合后37℃保温5 min,于593 nm测定吸光值。以Trolox作为标准品绘制标准曲线并计算,测定结果以每g样品相当于Trolox的物质的量（μmol）表示。

1.4.6 MDA含量 MDA含量的测定参考REN等^[20]的方法。2 g样品加入100 g?L^-1三氯乙酸溶液均质,4℃下13 000 r/min离心20 min,2 mL上清加入2 mL硫代巴比妥酸溶液煮沸20 min,冷却,分别于450、532和600 nm下测定吸光值。MDA含量如下公式计算,其中,V：提取液总体积（mL）;Vs：测定时所取样品提取液体积（mL）;W：样品重（g）。

$MDA\text{ }\!\!\mu\!\!\text{ mol}\cdot \text{k}{{\text{g}}^{\text{-1}}}\text{ }=\frac{\left[ \left( \text{6}\text{.45}\times \left( \text{O}{{\text{D}}_{\text{532}}}\text{-O}{{\text{D}}_{\text{600}}} \right)\text{-0}\text{.56}\times O{{D}_{\text{450}}} \right) \right]\times V}{W\times {{V}_{S}}}$

1.5 数据处理与分析

采用SPSS17.0软件对所有数据进行统计分析,利用邓肯氏多重比较法对不同处理组样品进行差异显著性分析,P<0.05表示差异显著,生理指标相关性采用Pearson相关性分析。采用origin 9.0软件绘图。

2 结果

2.1 UV-C处理对鲜切梨褐变程度的影响

表面褐变是影响鲜切梨货架期的重要因素之一。如图1所示,鲜切梨在贮藏初期呈亮白色,当贮藏至第12天时,3组样品均发生了不同程度的褐变,但两种UV-C处理组的褐变程度均低于对照组样品。与表观颜色变化相对应,鲜切梨的褐变指数（BI）在贮藏期间均呈上升趋势,但两种UV-C处理组样品的BI值上升较慢,且在12 d的贮藏过程中均显著低于对照组（P<0.05）,鲜切后UV-C处理组的BI值低于预UV-C处理,说明鲜切后UV-C处理更能有效控制鲜切梨贮藏期间的褐变。

图1

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图1UV-C处理对鲜切‘皇冠’梨贮藏过程中表面褐变的影响

不同字母表示处理间差异显著（P<0.05）。下同
Fig. 1Effect of UV-C treatment on the surface color of fresh-cut Huangguan pear during storage process

Different alphabets are significantly (P<0.05) different among different treated samples. The same as below

2.2 UV-C处理对鲜切梨PPO活性的影响

PPO是引起鲜切果蔬组织褐变的关键酶,如图2所示,鲜切梨的PPO活性在贮藏前2 d天略有下降,随着贮藏时间的延长,呈先上升后下降的趋势。两种UV-C处理组样品在贮藏前8 d时PPO活性要显著高于对照组,说明UV-C处理能够加速鲜切梨PPO的合成,其中预UV-C处理诱导PPO合成能力高于鲜切后UV-C处理,但同时其PPO活性下降也较快,当贮藏8 d以后显著低于对照组样品（P<0.05）,而鲜切后UV-C处理组在贮藏后期（10—12 d）PPO活性与对照组无显著差异（P>0.05）。

图2

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图2UV-C处理对鲜切‘皇冠’梨PPO活性的影响

Fig. 2Effect of UV-C treatment on the PPO activity of fresh-cut Huangguan pear during storage

2.3 UV-C处理对鲜切梨总酚含量和PAL活性的影响

多酚类物质是水果中重要的抗氧化物质,同时也是酶促褐变的底物。如图3-a所示,鲜切梨贮藏过程中多酚类物质的含量呈先上升后下降的趋势。机械伤害能够诱导多酚类物质的合成^[21,22],因此,在贮藏初期,总酚含量上升,随着贮藏时间延长,褐变程度加深,多酚类物质不断被消耗,含量逐渐下降。两种UV-C处理组样品的总酚含量在贮藏第2、8和12天时要显著低于对照组。PAL是苯丙烷代谢途径中合成酚类物质的限速酶,鲜切梨在贮藏期间的PAL活性变化趋势以及两种UV-C处理对PAL活性的影响与总酚含量基本一致,在贮藏过程中PAL活性呈先上升后下降的趋势,且两种UV-C处理显著降低PAL活性（图3-b）,但3组样品的PAL活性在贮藏前8 d一直呈上升趋势,而总酚含量却在此之前开始下降,可能是由于在贮藏过程中酚类物质由于褐变的消耗速率要高于其合成速度,由于对照组样品褐变程度最大,所以其总酚含量从第2天就开始下降。

图3

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图3UV-C处理对鲜切‘皇冠’梨总酚含量（a）和PAL活性（b）的影响

Fig. 3Effect of UV-C treatment on the total phenolic content (a) and PAL activity (b) of fresh-cut Huangguan pear during storage

2.4 UV-C处理对鲜切梨H₂O₂和MDA含量的影响

如图4-a所示,鲜切梨的H₂O₂含量贮藏2 d时略有下降,随后逐渐上升,两种UV-C处理组样品的H₂O₂含量均显著低于对照组样品（P<0.05）,但两种处理方式之间除了贮藏8 d外,并没有显著差异（P>0.05）。H₂O₂的积累导致膜脂过氧化程度不断加深,所以MDA的含量也逐渐升高,但在贮藏后期可能由于与蛋白发生交联反应,因而其含量逐渐下降。两种UV-C处理方式均能降低鲜切梨MDA的积累,但鲜切后UV-C处理效果更好。

图4

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图4UV-C处理对鲜切‘皇冠’梨H₂O₂（a）和MDA含量（b）的影响

Fig. 4Effect of UV-C treatment on the H₂O₂ (a) and MDA (b) contents of fresh-cut Huangguan pear during storage

2.5 UV-C处理对鲜切梨抗氧化酶活性的影响

SOD、CAT、APX和GR是果蔬体内重要的抗氧化酶。如图5-a所示,鲜切梨在贮藏过程中SOD活性呈先下降后上升的趋势,在贮藏6 d时,活性最低。鲜切后UV-C处理组样品在贮藏2—10 d中SOD活性均显著高于对照组（P<0.05）,而UV-C预处理组只有在贮藏6—10 d以后,SOD活性高于对照组（P<0.05）。鲜切梨的CAT活性在贮藏期间整体呈下降趋势,两种UV-C处理均能够延缓CAT活性的下降,其中鲜切后UV-C处理的延缓效果更好（图5-b）。如图5-c和5-d所示,鲜切梨的APX和GR活性在贮藏过程中均呈先上升后下降的趋势,3组鲜切梨样品的APX和GR活性均分别在贮藏2 d和4 d时达到最大,鲜切后UV-C处理一定程度上提高了鲜切梨的APX活性,而UV-C预处理对鲜切梨的APX活性无显著影响（P>0.05）,但能够显著提高鲜切梨的GR活性（P< 0.05）,且提高效果高于鲜切后UV-C处理。

图5

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图5UV-C处理对鲜切‘皇冠’梨SOD（a）、CAT（b）、APX（c）和GR（d）活性的影响

Fig. 5Effects of UV-C treatment on the activities of SOD (a), CAT (b), APX (c) and GR (d) of fresh-cut Huangguan pears during storage

2.6 UV-C处理对鲜切梨非酶抗氧化能力的影响

分别采用DPPH自由基和ABTS自由基清除能力以及还原能力来评价UV-C处理对鲜切梨非酶抗氧化能力的影响,结果如图6所示。鲜切梨在贮藏期间抗氧化能力呈下降趋势,鲜切后UV-C处理可以提高鲜切梨的抗氧化能力,但在贮藏过程中其抗氧化能力下降速度较快,贮藏6 d后,鲜切后UV-C处理组样品对DPPH自由基的清除能力和还原能力与对照组样品无显著差异,对ABTS自由基的清除能力在贮藏8 d后与对照组样品无显著差异（P>0.05）。与对照相比,UV-C预处理对鲜切梨的DPPH自由基清除能力以及还原能力无显著影响（P>0.05）,但在贮藏2—6 d时,其对ABTS自由基的清除能力显著高于对照组样品（P<0.05）。由此可见,鲜切后UV-C处理能更有效提高鲜切梨的非酶抗氧化能力。

图6

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图6UV-C处理对鲜切‘皇冠’梨DPPH自由基（a）和ABTS自由基（b）清除能力、还原能力（c）的影响

Fig. 6Effects of UV-C treatment on the DPPH radical (a) and ABTS radical (b) scavenging activities and reducing power (c) of fresh-cut Huangguan pears during storage

2.7 相关性分析

如图7所示,鲜切梨贮藏期间褐变程度（BI值）与H₂O₂和MDA含量以及PAL活性呈极显著正相关（P<0.01）,与CAT、APX和GR活性以及DPPH自由基和ABTS自由基清除能力、还原能力呈极显著负相关（P<0.01）。

图7

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图7BI与PPO活性等生理指标的相关性分析

Fig. 7Pearson correlation coefficients of BI and physiological parameters

3 讨论

切割伤害引发鲜切水果的表面褐变是影响其货架期的主要因素之一,本研究结果显示UV-C预处理后鲜切以及鲜切后UV-C处理均能够有效延缓鲜切梨的褐变。酶促褐变是一个复杂的过程,一般认为PPO在有氧条件下催化酚类物质形成邻苯醌,后者通过复杂的醌聚合反应形成褐色物质是酶促褐变发生的直接原因,在完整的细胞组织中,PPO主要存在于细胞质中,而酚类物质通常贮存和积累在液泡中,鲜切切割操作打破了酚酶的区域化分布,使PPO与酚类底物相遇,引起褐变的发生^[23]。当前许多研究采用的褐变控制方法均伴随着PPO活性的降低^[24,25],但是在本研究中,两种UV-C处理方式却使PPO活性提高,提示UV-C可能通过其他途径控制鲜切梨的褐变。HUQUE等^[26]研究表明鲜切苹果的PPO含量足以引起褐变的发生,其褐变的限制性因素是酚类物质的含量,在本研究中,两种UV-C处理后可以使总酚含量降低,这可能是其控制鲜切梨褐变因素之一。

近年来,越来越多研究表明酶促褐变不仅与酚类物质含量以及PPO的活性有关,还受细胞膜透性以及膜脂过氧化等多因素影响^[6]。CANTOS等^[27]研究认为鲜切马铃薯的褐变速度与PPO活性以及酚类物质浓度无关,细胞膜的完整性才是控制褐变速率的关键因素。同样,LI等^[28]的研究也发现膜是影响鲜切梨褐变的重要因素。细胞膜的破坏除了由于鲜切操作带来的直接机械损伤外,切割伤害引发大量ROS的产生,直接或间接启动膜脂过氧化反应,过氧化产物MDA使膜中的酶蛋白发生交联、聚合反应,引起细胞膜的损伤和破坏,最终导致细胞膜的区室化功能丧失,从而加快酶促褐变反应的发生^[29,30],减缓膜脂过氧化程度可以有效控制鲜切果蔬的褐变程度^[31]。随着贮藏时间的延长,鲜切梨的H₂O₂含量不断升高,膜脂过氧化程度逐渐加重,相关性分析结果显示鲜切梨的褐变程度与H₂O₂和MDA含量呈显著正相关,进一步证实了自由基引发的膜脂过氧化是加剧褐变的重要因素。笔者前期研究发现UV-C处理可以通过提高鲜切苹果的ROS代谢能力,减轻膜脂过氧化程度从而控制鲜切苹果的褐变^[13]。同时,UV-C处理还能提高鲜切杨桃贮藏过程中细胞膜的完整性,进而控制其褐变反应^[9]。本研究中,两种UV-C处理均能降低H₂O₂和MDA的积累,从而说明无论是鲜切前还是鲜切后UV-C处理,均可以通过降低ROS的积累以及减轻氧化损伤来控制鲜切梨的褐变。

ROS的大量积累会加剧酶促褐变反应,但同时果蔬自身拥有一套精准的抗氧化防御系统,能够及时清除ROS,因此,抗氧化防御系统在褐变控制过程中发挥重要的作用^[32]。切割伤害能够诱导鲜切果蔬的抗氧化酶活性提高以及抗氧化物质积累,因此在贮藏初期（前2 d）,鲜切梨的抗氧化酶（APX和GR）活性和总酚含量显著提高,而H₂O₂含量显著降低。随着贮藏时间的延长,果蔬组织逐渐衰老,其抗氧化防御能力也逐渐减弱,从而引起ROS大量积累,氧化损伤程度加重,最终加剧褐变反应。相关性分析结果也显示鲜切梨的H₂O₂和MDA含量分别与抗氧化酶活性（CAT和GR）和抗氧化能力（还原能力、DPPH自由基和ABTS自由基清除能力）呈显著或极显著负相关。研究表明UV-C处理能够提高鲜切紫甘蓝^[33]、鲜切石榴^[34]、鲜切红心萝卜^[35]的酶与非酶抗氧化能力,而鲜切果蔬抗氧化活性的提高,有助于控制其褐变的发生^[36,37]。在本研究中,两种UV-C处理均能不同程度的提高鲜切梨的抗氧化酶活性以及非酶抗氧化能力,说明UV-C处理控制鲜切梨的褐变与其提高抗氧化能力,减轻ROS引发的氧化损伤和膜脂过氧化密切相关。在今后通过进一步优化鲜切后UV-C处理工艺,以增强其对鲜切水果的褐变控制效果。

4 结论

无论是鲜切前UV-C预处理还是鲜切后UV-C处理5 min均能有效延缓鲜切梨的表面褐变,这种控制作用与PPO活性无关,主要是通过降低鲜切梨总酚含量,提高其抗氧化酶活性和非酶抗氧化能力,从而降低ROS的积累,减轻氧化损伤,保持膜的完整性,最终控制褐变的发生。两种处理方式相比,鲜切后UV-C处理更能有效提高鲜切梨的抗氧化能力,因而对褐变控制效果更好。

参考文献 View Option 原文顺序
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Food Science, 2014,35(2):12-17. (in Chinese)
DOI:10.7506/spkx1002-6630-201402003URL [本文引用: 1]
Response surface methodology (RSM) was employed to optimize liquid-to-material ratio, ethanol concentration,
ultrasound radiation time and temperature to obtain a high yield of polyphenols from banana peel by an ultrasonic-assisted
extraction technique. The antioxidant activities of polyphenols extracted from banana peel were evaluated by in vitro assays.
The results showed that the RSM model developed was able to describe the relationship between the factors (extraction
parameters) and the response variable (polyphenol yield). The optimized conditions were determined as follows: solventto-
solid ratio, 9:1 (mL/g); ethanol concentration, 54%; temperature, 53 ℃; and ultrasound radiation time, 43 min. Under
these conditions, the polyphenol yield obtained was 2.931%. The resulting extract exhibited significant 2,2-diphenyl-
1-picrylhydrazyl (DPPH), superoxide anion and hydroxyl radical scavenging activities, and the concentrations for 50%
inhibition (IC50) were 0.422 8, 0.255 2 and 0.243 9 mg/mL, respectively.

[17] CHEN C, HU W Z, ZHANG R D, JIANG A L, LIU C H. Effects of hydrogen sulfide on the surface whitening and physiological responses of fresh-cut carrots
Journal of the Science of Food and Agriculture, 2018,98(12):4726-4732.
DOI:10.1002/jsfa.9007URLPMID:29542138 [本文引用: 1]
BACKGROUND: The effect of hydrogen sulfide (H2 S) on the inhibition of the surface whitening of fresh-cut carrots was investigated. Whitening index; H2 O2 and malondialdehyde (MDA) contents; activities of catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD); and antioxidant capacities were evaluated. RESULTS: H2 S treatment significantly inhibited the surface whitening of fresh-cut carrots (P < 0.05), reduced the accumulation of H2 O2 and MDA, and enhanced antioxidant enzymes (CAT, APX and GR) activities and antioxidant capacities (P < 0.05). The PAL, PPO and POD activities of fresh-cut carrots were inhibited by treatment with H2 S (P < 0.05). Furthermore, correlation analysis revealed that whitening index was significantly positively correlated with H2 O2 content, lipid peroxidation, PPO and POD activities. CONCLUSION: H2 S inhibited the surface whitening of fresh-cut carrots by reducing H2 O2 accumulation and lipid peroxidation, and also inhibited PPO and POD activities. (c) 2018 Society of Chemical Industry.

[18] 李雪, 吴觉天, 王毅, 姜红, 毕阳, 司敏, 张静荣, 徐洁. 采后ABA处理促进‘陇薯3号’马铃薯块茎愈伤形成
中国农业科学, 2017,50(20):4003-4011.
DOI:10.3864/j.issn.0578-1752.2017.20.014URL [本文引用: 1]
【Objective】The experiment was conducted to study the effects of exogenous abscisic acid (ABA) treatment on wound healing of the potato tubers ‘Longshu No.3’, to analyze the role of phenylpropane metabolism and antioxidant enzymes in wound healing. 【Method】The potato cultivar ‘Longshu No.3’ was used as materials. The tubers were artificially damaged, then treated with different concentrations ABA, and healed under dark condition ((20±3)℃, RH (80±5)%). The healing ability of treated tubers was evaluated. The changes of activity of phenylpropane metabolism key enzymes, peroxidase and polyphenol oxidase were determined. The content of metabolites was determined at wounded site of tubers treated with 100mg·L^-1ABA during healing. The formation of healing tissue was observed by scanning electron microscopy. 【Result】ABA treatment at different concentrations effectively promoted wound healing of tubers, the screened optimum concentration was 100 mg·L^-1. ABA treatment at 100 mg·L^-1 significantly increased the activity of phenylalnine ammonialyase, cinnamic acid hydroxylase, 4-coumaroyl-coenzyme A-ligase and cinnamyl alcohol dehydrogenase, sped the accumulation of total phenols, flavonoids and lignin at wounded site of tubers. In which, the activity of phenylalanine ammonialyase showed bimodal change, the treatment was 253.07% and 125.18% higher than the control after 3 days and 9 days of healing. The content of total phenols and flavonoids of the treatment showed 48.60% and 50.42% higher than that of the control. Moreover, the activities of peroxidase and polyphenol oxidase were significantly enhanced at wounded site of tubers. Observation of scanning electron microscopy showed that the formation of closing layer and wound periderm of tubers were accelerated after ABA treatment. 【Conclusion】Exogenous ABA treatment accelerates the formation of wound periderm of potato tubers by promoting the phenylpropane metabolism, and increasing the activities of peroxidase and polyphenol oxidase.
LI X, WU J T, WANG Y, JIANG H, BI Y, SI M, ZHANG J R, XU J. Postharvest ABA treatment promote wound healing of potato ‘Longshu No.3’ tubers
Scientia Agricultura Sinica, 2017,50(20):4003-4011. (in Chinese)
DOI:10.3864/j.issn.0578-1752.2017.20.014URL [本文引用: 1]
【Objective】The experiment was conducted to study the effects of exogenous abscisic acid (ABA) treatment on wound healing of the potato tubers ‘Longshu No.3’, to analyze the role of phenylpropane metabolism and antioxidant enzymes in wound healing. 【Method】The potato cultivar ‘Longshu No.3’ was used as materials. The tubers were artificially damaged, then treated with different concentrations ABA, and healed under dark condition ((20±3)℃, RH (80±5)%). The healing ability of treated tubers was evaluated. The changes of activity of phenylpropane metabolism key enzymes, peroxidase and polyphenol oxidase were determined. The content of metabolites was determined at wounded site of tubers treated with 100mg·L^-1ABA during healing. The formation of healing tissue was observed by scanning electron microscopy. 【Result】ABA treatment at different concentrations effectively promoted wound healing of tubers, the screened optimum concentration was 100 mg·L^-1. ABA treatment at 100 mg·L^-1 significantly increased the activity of phenylalnine ammonialyase, cinnamic acid hydroxylase, 4-coumaroyl-coenzyme A-ligase and cinnamyl alcohol dehydrogenase, sped the accumulation of total phenols, flavonoids and lignin at wounded site of tubers. In which, the activity of phenylalanine ammonialyase showed bimodal change, the treatment was 253.07% and 125.18% higher than the control after 3 days and 9 days of healing. The content of total phenols and flavonoids of the treatment showed 48.60% and 50.42% higher than that of the control. Moreover, the activities of peroxidase and polyphenol oxidase were significantly enhanced at wounded site of tubers. Observation of scanning electron microscopy showed that the formation of closing layer and wound periderm of tubers were accelerated after ABA treatment. 【Conclusion】Exogenous ABA treatment accelerates the formation of wound periderm of potato tubers by promoting the phenylpropane metabolism, and increasing the activities of peroxidase and polyphenol oxidase.

[19] CHEN C, HU W Z, ZHANG R D, JIANG A L, ZOU Y. Levels of phenolic compounds, antioxidant capacity, and microbial counts of fresh-cut onions after treatment with a combination of nisin and citric acid
Horticulture, Environment, and Biotechnology, 2016,57(3):266-273.
DOI:10.1007/s13580-016-0032-xURL [本文引用: 1]

[20] REN Y L, WANG Y F, BI Y, Ge Y H, Wang Y, Fan C F, Li D Q, Deng H W. Postharvest BTH treatment induced disease resistance and enhanced reactive oxygen species metabolism in muskmelon ( Cucumis melo L.) fruit
European Food Research and Technology, 2012,234(6):963-971
DOI:10.1007/s00217-012-1715-xURL [本文引用: 1]
Benzo (1, 2, 3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) is a novel synthetic elicitor capable of inducing disease resistance in many plants. Fruits were dipped in BTH at 100 mg/L for 10 min, and then stored at room temperature (22 +/- A 2 A degrees C, relative humidity 55-60 %). The results showed that BTH significantly ( < 0.05) reduced the lesion area of fruits inoculated with and the natural disease incidence of fruits during storage at room temperature. The treatment effectively maintained cell membrane integrity and decreased the production of lipid peroxidation and malondialdehyde. BTH treatment markedly enhanced the accumulation of hydrogen peroxide, (H2O2) while decreased the rate of superoxide anion (O (2) (center dot-) ) production. Furthermore, BTH observably increased the activities of NADPH oxidase (NOX, EC1.6.3.1), superoxide dismutase (SOD, EC1.15.1.1), peroxidase (POD, EC1.11.1.7), ascorbate peroxidase (APX, EC1.11.1.11), and glutathione reductase (GR, EC1.6.4.2), while inhibited the catalase (CAT, EC1.11.1.6) activity. These results indicated that BTH treatment increased the disease resistance of muskmelon fruits by enhancing their antioxidant system activity after harvest, and suggested that postharvest treatment with BTH could be promising in reducing decay and reducing or/and substituting chemical fungicides to control postharvest diseases in fruits.

[21] REYES L F, CISNEROS-ZEVALLOS L. Wounding stress increases the phenolic content and antioxidant capacity of purple-flesh potatoes ( Solanum tuberosum L.)
Journal of Agricultural and Food Chemistry, 2003,51(18):5296-5300.
DOI:10.1021/jf034213uURLPMID:12926873 [本文引用: 1]
Several abiotic stresses, including ethylene, methyl jasmonate, temperature, light, and wounding, were tested for their ability to induce accumulation of phenolic compounds and antioxidant capacity in purple-flesh potatoes (cv. All Blue). Results indicated that temperature, ethylene, methyl jasmonate, and light treatments did not significantly affect the accumulation of phenolic compounds compared to control samples. Only tubers with low initial anthocyanin levels treated with methyl jasmonate showed approximately 60% anthocyanin accumulation. Wounding induced the accumulation of phenolics compounds and an increase of PAL-activity in sliced tissue compared to the control. Total phenolics increased approximately 60% with a parallel 85% increase in antioxidant capacity. These results show that selection of appropriate abiotic stresses can enhance the nutritional and functional value of potatoes.

[22] VIACAVA F, SANTANA-GáLVEZ J, HEREDIA-OLEA E, PéREZ- CARRILLO E, NAIR V, CISNEROS-ZEVALLOS L, JACOBO- VELáZQUEZ D A. Sequential application of postharvest wounding stress and extrusion as an innovative tool to increase the concentration of free and bound phenolics in carrots
Food Chemistry, 2020,307:125551.
DOI:10.1016/j.foodchem.2019.125551URLPMID:31648173 [本文引用: 1]
Postharvest wounding stress in carrots induces the accumulation of phenolics, whereas extrusion generates modifications in the nutritional profiles of food matrixes. In the present study, the sequential application of wounding stress and extrusion on total free and bound phenolics as well as on carotenoid profiles of carrots was evaluated. Wounding was applied by shredding carrots and storing the tissue (48h, 15 degrees C). The stressed-tissue was dehydrated and extruded at 63 degrees C or 109 degrees C and at continuous or expansion screw configurations. Extrudates were milled and sieved before phytochemical analysis. Wounding increased total free (288.1%) and bound (407.6%) phenolic content, whereas the carotenoid content was unaltered. The free and bound phenolics that showed the highest increase due to wounding were the chlorogenic (579.8%) and p-coumaric (390.9%) acids. Extrusion, at 109 degrees C under expansion screw configuration, further increased the wound-induced accumulation of total free (296.6%) and bound (22.1%) phenolics and induced trans-cis isomerization of beta-carotene.

[23] LANDRIGAN M, MORRIS S C, EAMUS D, MCGLASSON W B. Postharvest water relationships and tissue browning of rambutan fruit
Scientia Horticulturae, 1996,66(3/4):201-208.
DOI:10.1016/S0304-4238(96)00915-6URL [本文引用: 1]

[24] RICO D, MARTíN-DIANA A B, BARAT J M, BARRY-RYAN C. Extending and measuring the quality of fresh-cut fruit and vegetables: A review
Trends in Food Science and Technology, 2007,18(7):373-386.
DOI:10.1016/j.tifs.2007.03.011URL [本文引用: 1]

[25] OMS-OLIU G, ROJAS-GRAü M A, GONZáLEZ L A, VARELA P, SOLIVA-FORTUNY R, HERNANDO M I H, MUNUERA I P, FISZMAN S. MARTíN-BELLOSO O. Recent approaches using chemical treatments to preserve quality of fresh-cut fruit: A review
Postharvest Biology and Technology, 2010,57(3):139-148.
DOI:10.1016/j.postharvbio.2010.04.001URL [本文引用: 1]

[26] HUQUE R, WILLS R B H, PRISTIJONO P, GOLDING J B. Effect of nitric oxide (NO) and associated control treatments on the metabolism of fresh-cut apple slices in relation to development of surface browning
Postharvest Biology and Technology, 2013,78:16-23.
DOI:10.1016/j.postharvbio.2012.12.006URL [本文引用: 1]
Surface browning is an important cause of deterioration of fresh-cut apples during postharvest handling. 'Granny Smith' apple slices treated with NO gas (10 mu L/L) and the NO donor compound 2,2'-(hydroxynitrosohydrazino)-bisethanamine (diethylenetriamine nitric oxide (DETANO) (10 mg/L) dissolved in phosphate buffer (pH 6.5) showed delayed development of surface browning during storage at 5 degrees C and also resulted in a lower level of total phenols, inhibition of PPO activity, reduced ion leakage and reduced rate of respiration but had no significant effect on ethylene production or lipid peroxide level as measured by malondialdehyde (MDA) and hydrogen peroxide levels. The two control treatments of phosphate buffer (pH 6.5) and water dips also had significant effects compared to untreated slices. The relative effectiveness of treatments in extending postharvest life and reducing total phenols, PPO activity, ion leakage and respiration was DETANO > NO gas > phosphate buffer > water > untreated. Apple slices dipped in chlorogenic acid dissolved in water showed surface browning soon after application but dipping in DETANO solution negated the effect of chlorogenic acid whether applied before or after dipping in chlorogenic acid solution while the buffer and NO gas were also effective. It is suggested that an increase in phenols occurs on the apple surface soon after cutting, possibly as a defensive mechanism of the apple to limit damage to surface cells. The effectiveness of the applied treatments to inhibit development of surface browning may relate to their ability to minimize the level of phenols active on the cut surface possibly in conjunction with a reduced PPO activity. (c) 2012 Elsevier B.V.

[27] CANTOS E, TUDELA J A, GIL M I, ESPíN J C. Phenolic compounds and related enzymes are not rate-limiting in browning development of fresh-cut potatoes
Journal of Agricultural and Food Chemistry, 2002,50(10):3015-3023.
DOI:10.1021/jf0116350URLPMID:11982435 [本文引用: 1]
The effect of minimal processing on polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia-lyase (PAL), and phenolic compounds was studied in five potato cultivars (Agria, Cara, Liseta, Monalisa, and Spunta). Minimal processing caused an overall increase in PPO, POD, and PAL activities. The isoform pattern of PPO was the same for all of the cultivars before and after processing. No latent PPO was detected. The isoperoxidase pattern was approximately the same among cultivars. An increase in POD activity was related to the specific induction of an acidic isoperoxidase. PAL showed an induction pattern characterized by the presence of a maximum peak of activity after 4 days of processing for all of the cultivars. The sequence of browning susceptibility of potato cultivars was as follows: Monalisa > Spunta > Liseta > Cara > Agria. Browning development was only partially correlated to PAL activity (only during the first 4 days after wounding). However, this correlation could not explain the above sequence of browning susceptibility. Minimal processing caused an increase of chlorogenic acid, whereas tyrosine content remained unchanged. In summary, no significant correlation was found between either rate or degree of browning and any other biochemical and physiological attribute investigated (PPO, POD, hydrogen peroxide, ascorbic acid content, and initial phenolics content as well as total and individual phenolics accumulation).

[28] LI Z H, ZHANG Y, GE H B. The membrane may be an important factor in browning of fresh-cut pear
Food Chemistry, 2017,230:265-270.
DOI:10.1016/j.foodchem.2017.03.044URLPMID:28407910 [本文引用: 1]
Surface browning is an important cause of deterioration of fresh-cut fruit during postharvest handling. In this paper, four pear cultivars with different extents of natural browning were selected to analyse the factors involved in browning. The main results are as follows: the lipoxygenase (LOX) activity of 'Mantianhong' and 'Yali' pears was higher accompanied by a stronger degree of browning, while the LOX activity in 'Xueqing' and 'Xinli 7' pears was lower, with less browning. A higher unsaturated fatty acid ratio of pear resulted in reduced browning. The cell membranes disappeared 30min after being cut in 'Mantianhong' pear, which browns easily; however, the cell membranes were still intact 30min after being cut in 'Xueqing' pear, which does not brown easily. Therefore, it can be assumed that the stability of the cell membrane plays an important role in inhibiting browning of fresh-cut pears.

[29] JIANG J, JIANG L, ZHANG L, LUO H B, OPIYO A M, YU Z F. Changes of protein profile in fresh-cut lotus tuber before and after browning
Journal of Agricultural and Food Chemistry, 2012,60(15):3955-3965.
DOI:10.1021/jf205303yURL [本文引用: 1]
Browning is a critical problem, which often limits the shelf life and marketability in fresh-cut lotus tuber. Proteome level changes in response to the browning metabolism were investigated using two-dimensional electrophoresis (2-DE) and MALDI-TOF-TOF. A total of 34 functional protein spots were identified by comparing 2-DE protein patterns of fresh-cut lotus tuber before and after browning. These 34 identified proteins could be classified into 7 functional groups based on the NCBI database, that is, material and energy metabolism (35%), stress response (20%), respiration metabolism (12%), cell structure (12%), signal transduction (6%), gene expression regulation (6%), and unclassified proteins (9%). The group with the greatest difference in protein expression was related to material metabolism and regulation, reactive oxygen species metabolism, and respiratory control. The distinct proteins included universal stress protein (USP), superoxide dismutase (SOD), peroxidase (POD), ferritin, and ATPase.

[30] LIN Y F, LIN H T, LIN Y X, ZHANG S, CHEN Y H, JIANG X J. The roles of metabolism of membrane lipids and phenolics in hydrogen peroxide-induced pericarp browning of harvested longan fruit
Postharvest Biology and Technology, 2016,111:53-61.
DOI:10.1016/j.postharvbio.2015.07.030URL [本文引用: 1]

[31] GAO H, CHAI H K, CHENG N, CAO W. Effects of 24-epibrassinolide on enzymatic browning and antioxidant activity of fresh-cut lotus root slices
Food chemistry, 2017,217:45-51.
DOI:10.1016/j.foodchem.2016.08.063URLPMID:27664606 [本文引用: 1]
Fresh-cut lotus root slices were treated with 80nM 24-epibrassinolide (EBR) and then stored at 4 degrees C for 8days to investigate the effects on cut surface browning. The results showed that EBR treatment reduced cut surface browning in lotus root slices and alleviated membrane lipid peroxidation as reflected by low malondialdehyde content and lipoxygenase activity. EBR treatment inhibited the activity of phenylalanine ammonia lyase and polyphenol oxidase, and subsequently decreased phenolics accumulation and soluble quniones formation. The treatment also stimulated the activity of peroxidase, catalase and ascorbate peroxidase and delayed the loss of ascorbic acid, which would help prevent membrane lipid peroxidation, as a consequence, reducing decompartmentation of enzymes and substrates causing enzymatic browning. These results indicate that EBR treatment is a promising attempt to control browning at cut surface of fresh-cut lotus root slices.

[32] MITTLER R. Oxidative stress, antioxidants and stress tolerance
Trends in Plant Science, 2002,7(9):405-410.
DOI:10.1016/s1360-1385(02)02312-9URLPMID:12234732 [本文引用: 1]
Traditionally, reactive oxygen intermediates (ROIs) were considered to be toxic by-products of aerobic metabolism, which were disposed of using antioxidants. However, in recent years, it has become apparent that plants actively produce ROIs as signaling molecules to control processes such as programmed cell death, abiotic stress responses, pathogen defense and systemic signaling. Recent advances including microarray studies and the development of mutants with altered ROI-scavenging mechanisms provide new insights into how the steady-state level of ROIs are controlled in cells. In addition, key steps of the signal transduction pathway that senses ROIs in plants have been identified. These raise several intriguing questions about the relationships between ROI signaling, ROI stress and the production and scavenging of ROIs in the different cellular compartments.

[33] ZHANG J, YUAN L, LIU W, LIN Q, WANG Z D, GUAN W Q. Effects of UV-C on antioxidant capacity, antioxidant enzyme activity and colour of fresh-cut red cabbage during storage
International Journal of Food Science and Technology, 2017,52(3):626-634.
DOI:10.1111/ijfs.2017.52.issue-3URL [本文引用: 1]

[34] MAGHOUMI M, GóMEZ P A, MOSTOFI Y, ZAMANI Z, ARTéS- HERNáNDEZ F, ARTéS F. Combined effect of heat treatment, UV-C and superatmospheric oxygen packing on phenolics and browning related enzymes of fresh-cut pomegranate arils
LWT-Food Science and Technology, 2013,54(2):389-396.
DOI:10.1016/j.lwt.2013.06.006URL [本文引用: 1]

[35] 高梵, 龙清红, 韩聪, 金鹏, 郑永华. UV-C处理对鲜切红心萝卜抗氧化活性的影响
食品科学, 2016,37(11):12-17.
DOI:10.7506/spkx1002-6630-201611003URL [本文引用: 1]
The effect of ultraviolet-C (UV-C) treatment at different dosages on antioxidant system and antioxidant activity of
fresh-cut red-fleshed radish was investigated. The fresh-cut radish was treated with 0, 0.25, 0.5, 1.0 and 2.0 kJ/m2 of UV-C
and then stored at 5 ℃ for up to 48 h. The results indicated that 1.0 kJ/m2 UV-C treatment had the most significant effect
on inducing the synthesis and accumulation of phenolics and increasing the 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical
scavenging activity of fresh-cut radish during storage. This UV-C treatment also induced the accumulation of anthocyanins
and flavonoids, retarded the decrease of ascorbic acid content and enhanced the activities of antioxidant enzymes. These
results suggest that UV-C treatment could increase the antioxidant activity of fresh-cut red-fleshed radish by inducing the
synthesis of phenolic compounds and enhancing the activities of antioxidant enzymes.
GAO F, LONG Q H, HAN C, JIN P, ZHENG Y H. Effect of UV-C treatment on antioxidant activity of fresh-cut red-fleshed radish
Food Science, 2016,37(11):12-17. (in Chinese)
DOI:10.7506/spkx1002-6630-201611003URL [本文引用: 1]
The effect of ultraviolet-C (UV-C) treatment at different dosages on antioxidant system and antioxidant activity of
fresh-cut red-fleshed radish was investigated. The fresh-cut radish was treated with 0, 0.25, 0.5, 1.0 and 2.0 kJ/m2 of UV-C
and then stored at 5 ℃ for up to 48 h. The results indicated that 1.0 kJ/m2 UV-C treatment had the most significant effect
on inducing the synthesis and accumulation of phenolics and increasing the 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical
scavenging activity of fresh-cut radish during storage. This UV-C treatment also induced the accumulation of anthocyanins
and flavonoids, retarded the decrease of ascorbic acid content and enhanced the activities of antioxidant enzymes. These
results suggest that UV-C treatment could increase the antioxidant activity of fresh-cut red-fleshed radish by inducing the
synthesis of phenolic compounds and enhancing the activities of antioxidant enzymes.

[36] HU K D, QIAN W, HU L Y, GAO S P, WU J, LI Y H, ZHENG J L, HAN Y, LIU Y S, ZHANG H. Hydrogen sulfide prolongs postharvest storage of fresh-cut pears (Pyrus pyrifolia) by alleviation of oxidative damage and inhibition of fungal growth
PLoS ONE, 2014,9(1):e85524.
DOI:10.1371/journal.pone.0085524URLPMID:24454881 [本文引用: 1]
Hydrogen sulfide (H2S) has proved to be a multifunctional signaling molecule in plants and animals. Here, we investigated the role of H2S in the decay of fresh-cut pears (Pyrus pyrifolia). H2S gas released by sodium hydrosulfide (NaHS) prolonged the shelf life of fresh-cut pear slices in a dose-dependent manner. Moreover, H2S maintained higher levels of reducing sugar and soluble protein in pear slices. H2S significantly reduced the accumulation of hydrogen peroxide (H2O2), superoxide radicals (*O2(-)) and malondialdehyde (MDA). Further investigation showed that H2S fumigation up-regulated the activities of antioxidant enzymes ascorbate peroxidase (APX), catalase (CAT), and guaiacol peroxidase (POD), while it down-regulated those of lipoxygenase (LOX), phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO). Furthermore, H2S fumigation effectively inhibited the growth of two fungal pathogens of pear, Aspergillus niger and Penicillium expansum, suggesting that H2S can be developed as an effective fungicide for postharvest storage. The present study implies that H2S is involved in prolonging postharvest storage of pears by acting as an antioxidant and fungicide.

[37] ZHENG J L, HU L Y, HU K D, WU J, YANG F, ZHANG H. Hydrogen sulfide alleviates senescence of fresh-cut apple by regulating antioxidant defense system and senescence-related gene expression
HortScience, 2016,51(2):152-158.
DOI:10.21273/HORTSCI.51.2.152URL [本文引用: 1]