不同猕猴桃品种果实剥皮性状研究

黄丽红,伍梦婷,钟文奇,陶俊杰,贾慧敏,黄春辉*

(江西农业大学农学院·江西农业大学猕猴桃研究所,南昌 330045)

摘 要:【目的】 比较不同猕猴桃品种在软熟期果实剥皮性状的变化,建立猕猴桃果实剥皮性状综合评价体系,客观反映不同猕猴桃品种间果实剥皮难易程度的差异性。【方法】以25个猕猴桃品种为材料,对不同猕猴桃品种软熟期的果实先进行手动撕拉,通过观测皮肉分离过程中的“剥皮数”和“剥离度”两个参数来进行判断和评估,再结合基于力学测量装置构建的猕猴桃剥离器对不同猕猴桃品种进行剥皮力的测定。【结果】不同猕猴桃品种软熟期果实的剥皮数、剥离度及剥皮力不同。通过综合比较25个猕猴桃品种的果实剥皮数、剥离度和剥皮力得出:16个中华猕猴桃品种中金丰相对其他品种剥皮次数较少为18次,剥离度评价等级最高为3~4分,果肉受损程度较低,其次是金奉,在与其他品种剥皮数和剥离度评价等级相差不大的情况下,其所需的剥皮力平均值最小为0.42 N;果实大小一致的4个美味猕猴桃品种中米良1号相对其他品种剥皮数与剥离度相差不大,但所需剥皮力平均值为0.38 N,显著小于其他品种,果皮更易剥落且果肉受损程度更低;5个毛花猕猴桃品种中华特果皮最厚,果皮剥落顺畅,但所需剥皮力较大平均值为1.03 N,赣绿1号剥皮次数最少为7次,剥离度评价等级最高为7~8分且所需剥皮力平均值仅为0.47 N,相对其他品种更易剥皮且不费力,赣猕6号剥离度评价等级为5~6分,剥皮数最多为13次,相对其他品种更难剥皮。【结论】不同种类猕猴桃果实剥皮性状差异较大,其中毛花猕猴桃果实最容易剥皮,且在同一种类不同猕猴桃品种间的果实剥皮性状差异也较大,25个猕猴桃品种中毛花猕猴桃赣绿1号剥皮数最少、剥离度评价等级最高、剥皮力较小,因此是最容易剥皮的。

关键词:猕猴桃;果实;剥皮性状;剥皮数;剥皮力

猕猴桃隶属猕猴桃科(Actinidiaceae)猕猴桃属(Actinidia Lindl.),是一种原产于中国的藤本果树[1]。猕猴桃果实因具有独特的风味,富含多种维生素、有机酸、膳食纤维、多糖、矿物质元素及多种人体必需的氨基酸等营养成分而深受国内外消费者喜爱[2]。自2009 年开始,中国猕猴桃年产量和进口量均居世界第一,已成为全球最大的猕猴桃生产国和消费国[3]

随着人们生活水平的提高,消费者对水果的食用方便与卫生程度越来越重视,尤其对于一些需要剥皮食用的水果,如猕猴桃[4-6]、枇杷[7]、柑橘[8-10]等,其剥皮难易程度也已成为被选择食用的重要因素之一。尤其对于中国商业化栽培的中华猕猴桃(A.chinensis var. chinensis)和美味猕猴桃(A. chinensis var.deliciosa),其果皮均不可食用,且通常剥皮食用时双手会沾满黏稠的汁液,这种不便极大影响了消费者对猕猴桃的选择[11]。而中国特有且丰富的毛花猕猴桃(A.eriantha)除了具有较高的营养价值外,与其他种类的猕猴桃相比,最大的特点就是果皮容易剥离[12-14],但绝大部分还处于野生状态,只有极少数品种应用于生产中[15]

水果中对柑橘[16]、香蕉[17]果皮剥离的研究最为广泛,但在猕猴桃上却鲜有研究,且大多集中在果皮结构、果皮细胞中果胶物质和半乳糖方面[5,18-19]。虽然研究表明果实剥皮性状受到品种的影响[20],但对于不同猕猴桃种类间的剥皮性状差异,以及各个种类不同猕猴桃品种之间的剥皮性状差异,却尚未有客观的评价方法。目前关于猕猴桃果实剥皮性状的评价主要是通过人为主观赋值划分等级“剥离度”或计算手动撕拉果皮使皮肉分离过程中的“剥皮数”2个参数来进行判断和评估[4,19,21],这种方法直观简便,成本较低,且不需要借助特殊的仪器设备、专用检验场所,但存在主观性强、精确性差等缺点,不利于对猕猴桃果实剥皮性状的客观描述与界定。因无法客观反映果实剥皮性状,直接影响了该性状生理和分子层面上的深入研究。在此基础上,笔者基于力学测量装置构建了一个可以对不同品种猕猴桃果实剥皮性状进行观测比较的体系,从而可以更加客观全面的对猕猴桃果实剥皮性进行分析评估,为后续深入研究猕猴桃剥皮性的生理和分子机制奠定基础。

1 材料和方法

1.1 供试材料

试验材料采自江西省奉新县农业农村局猕猴桃种质资源圃(E 115°38′,N 28°70′)中栽植的不同猕猴桃品种。于果实达到商业采摘标准时,选择大小一致、无病虫害的果实进行采集,室温放置直至软熟(果皮硬度<600g)时进行果实剥皮数、剥离度及剥皮力的检测分析。每个品种设3 次生物学重复,每次重复10个果实。

1.2 试验方法

1.2.1 不同猕猴桃品种的果实剥皮数和果皮剥离度 果实剥皮数是指从花柱端向果柄端进行手动撕拉,整个果实所剥离下来的果皮数[4]

果皮剥离度通过赋值分数来进行评价,赋值分数根据果皮与果肉剥离程度共分为5个等级[21],即:

(1)果皮完全不能与果肉剥离,剥皮过程中果肉碎裂,完全粘皮,赋值0分;

(2)果皮剥离困难,剥皮过程中80%以上果肉受损,表现较粘皮,赋值1~2分;

(3)果皮剥离较困难,剥皮过程中40%~80%果肉受损,表现较粘皮,赋值3~4分;

(4)果皮较易剥离,剥皮过程中5%~40%果肉受损,表现较离皮,赋值5~6分;

(5)果皮易剥离,剥皮过程中小于5%果肉受损,表现离皮,赋值7~8分。

1.2.2 不同猕猴桃品种的果实剥皮力 为更加客观地评价不同猕猴桃品种果实剥皮性的差异,参考张晓楠等[8-9]测量柑橘的果皮与果肉间的黏力和果皮穿透阻力的设备和Harker等[18]用玻璃棒滚动或手动撕拉将猕猴桃果皮果肉进行分离的方法,笔者课题组制作了一个简易剥离器(图1)来测定剥皮所需力的大小。其原理和具体操作如下:操作端将软熟期的猕猴桃固定在剥离器基座的主轴上;在果实赤道部切开一个口子,挑起果皮固定在金属夹上;用单股单芯硬铜线将金属夹连接到安装在移动横杆上的称重传感器上。横杆以固定速度在固定方位上移动,以果皮果肉开始分离到果皮完全剥落整个过程中传感器上力的变化为果实的动态剥皮力,并且该动态剥皮力的数值会实时显示在电脑端。每个猕猴桃果实进行东南西北4 个方位上剥皮力的测定,平均值即为该猕猴桃果实的剥皮力。

图1 测量猕猴桃果实剥皮力的设备
Fig.1 The apparatus for measuring the peeling power of kiwifruit

1.3 数据处理

利用Microsoft Excel 2019软件进行试验数据的处理,采用IBM SPSS Statistics 22.0软件进行显著性分析(p<0.05)。应用Photoshop 2021 软件及Origin 2018软件进行果实图片的处理及折线图的绘制。

2 结果与分析

2.1 不同猕猴桃品种的果实剥皮数和果皮剥离度

不同猕猴桃品种软熟期果实剥皮数和果皮剥离度不同。从表1和图2可知,25个猕猴桃品种中,相比于中华猕猴桃和美味猕猴桃,毛花猕猴桃的剥皮次数明显更少且剥离度等级更高。16 个中华猕猴桃品种剥皮过程中果肉受损程度最低的是金丰,剥离度评价等级最高赋值为3~4 分,其次是金奉、金圆、璞玉、魁蜜;果实大小一致的不同猕猴桃品种比较,金丰果实剥皮次数最少为18次,其次是金圆、金艳和金果,而早鲜、庐山香、红实2号、井魁的剥皮数较多,剥皮次数均大于50 次。4 个美味猕猴桃品种剥皮过程中果肉受损程度相对较低的分别有贵长、米良1 号、海沃德,其剥离度评价等级赋值为1~2分,金魁的果肉受损程度较高;果实大小一致的不同猕猴桃品种比较,贵长果实剥皮次数最少为20 次,其次是米良1 号、金魁、海沃德。5 个毛花猕猴桃品种中赣绿1号果实剥皮次数最少为7次,且剥皮过程中果肉受损程度最低,其剥离度评价等级赋值为7~8 分,其余毛花猕猴桃品种剥离度评价等级均赋值5~6 分;如图2 所示,在剥皮过程中发现华特猕猴桃相对其他毛花猕猴桃品种果皮更厚重,赣绿1 号果皮相对更轻薄,赣猕6 号猕猴桃果实在剥皮过程中果肉受损程度相对较高,剥皮次数达到了13 次,较其他4个毛花猕猴桃品种更多。

表1 不同猕猴桃品种的果实剥皮数和果皮剥离度
Table 1 Peel number and peel degree of different kiwifruit varieties

种类Species中华猕猴桃A.chinensis var.chinensis剥离度Detachability 000 1~2 3~4 00000 1~2 1~2 00美味猕猴桃A.chinensis var.deliciosa剥皮数Peel number 48 49 52 34 18 35 36 49 49 65 40 32 38 50 39 60 20 32 30 40毛花猕猴桃A.eriantha品种Varieties红阳Hongyang东红Donghong红实2号Hongshi No.2金圆Jinyuan金丰Jinfeng金艳Jinyan金果Jinguo万鼎1号Wanding No.1云海1号Yunhai No.1早鲜Zaoxian魁蜜Kuimi金奉Jin Feng翠玉Cuiyu井魁Jingkui璞玉Puyu庐山香Lushanxiang贵长Guichang金魁Jinkui米良1号Miliang No.1海沃德Hayward华特Wite赣绿6号Ganlü No.6赣猕6号Ganmi No.6赣绿1号Ganlü No.1赣绿2号Ganlü No.2纵径Longitudinal diameter/mm 60.39 57.18 55.41 54.13 58.77 64.27 68.11 47.48 60.70 59.78 51.29 59.37 55.37 63.65 60.17 59.91 53.41 52.61 70.75 58.91 59.80 47.69 49.39 53.19 54.66横径Transverse diameter/mm 43.80 48.25 50.85 49.31 45.98 44.22 47.34 53.79 51.26 50.41 60.23 40.96 50.46 45.22 47.43 55.24 36.02 49.42 43.58 49.53 24.95 28.30 28.09 25.59 27.33侧径Transverse diameter/mm 39.60 40.77 42.86 44.12 43.20 42.30 41.90 42.40 44.74 47.48 52.41 40.31 44.43 44.17 46.38 48.36 31.53 44.51 40.87 44.78 24.85 26.04 27.35 24.30 25.20果形指数Fruit shape index 1.38 1.19 1.09 1.10 1.28 1.45 1.44 0.88 1.18 1.19 0.85 1.45 1.10 1.41 1.27 1.09 1.48 1.07 1.62 1.19 2.40 1.69 1.76 2.08 2.00单果质量Mass per fruit/g 75.66 76.08 77.91 77.99 74.06 79.89 81.16 73.46 84.74 87.37 96.67 62.64 72.33 83.28 84.82 103.70 37.49 76.27 73.15 78.35 25.38 20.02 25.47 17.98 22.54 87 13 79 1~2 0 1~2 0 1~2 1~2 5~6 5~6 5~6 7~8 5~6

图2 不同猕猴桃品种的果实剥皮数
Fig.2 Peel number of different kiwifruit varieties

2.2 不同猕猴桃品种的果实剥皮力

猕猴桃测力装置测力过程中力的变化过程如图3 所示。从0 逐渐上升的剥皮力数值表示测量时果实皮肉逐渐分离过程中所需的力,当剥皮力达到峰值时则代表果皮完全剥落所需的力。

图3 猕猴桃测力装置测力过程中力的变化过程
Fig.3 The change process of force in force measuring device of kiwifruit

多次重复测量不同猕猴桃品种剥皮力数据的结果显示(图4),所有数据均在有效数据范围内,未出现异常值,体现了剥皮装置的稳定性及可靠性。不同猕猴桃品种果实剥皮力存在差异,25个猕猴桃品种中,东红所需的剥皮力最大为1.68 N,其次是红实2号、金丰、翠玉,而金果、云海1号、金奉、万鼎1号、米良1号、赣绿1号所需剥皮力较低。此外,16种中华猕猴桃中金奉所需剥皮力平均值最小为0.42 N,其次是万鼎1号、金果、云海1号;4种美味猕猴桃中米良1 号所需剥皮力平均值最低为0.38 N,而海沃德、金魁、贵长所需剥皮力较大;5 种毛花猕猴桃中赣绿1 号所需剥皮力平均值最小为0.47 N,其次是赣猕6 号、赣绿2 号,而华特和赣绿6 号所需剥皮力较大,平均值分别为1.03 N和1.06 N。

图4 不同猕猴桃品种剥皮力箱线图
Fig.4 Boxplot of peeling force of different varieties of kiwifruit

3 讨 论

果实的剥皮性状本身就是一个复合型的性状,因此,其评价指标也不是单一的。根据剥皮数和剥离度两个评价指标,发现在不同种类(中华猕猴桃、美味猕猴桃和毛花猕猴桃)的猕猴桃果实软熟期毛花猕猴桃更容易剥皮,需要的剥皮次数更少并且剥离度评价等级更高,这与前人结果研究也是一致的[5,18-19],但是仅根据这两个评价指标无法客观比较各个猕猴桃种类的不同猕猴桃品种间的差异。因此,笔者在本研究中基于力学测量装置构建了一个可以对猕猴桃果实剥皮性状进行观测比较的体系,通过制作简易的剥离器对不同猕猴桃品种进行剥皮力的测定,能够更加客观的反映果实剥皮性状的变化。这种结合力学装置对果实果皮的剥皮性进行定量测定的方法在柑橘[8-9]和猕猴桃[18]研究中同样有应用,张晓楠等[8-9]在柑橘中测量果皮黏力即本研究中的剥皮力主要是将数字测力计垂直固定在测力计上,用夹子夹紧果皮任何一端,然后用镊子将果肉部分垂直向下拉;Harker 等[18]在对猕猴桃果皮果肉进行分离时用的是玻璃棒滚动或手动撕拉,且速度为人为控制的缓慢而稳定;而在本研究中是将测力计水平固定在测力架,果实也同样固定在测力架另一端,通过带绳子的夹具将果皮与测力计连接进行力的测定,相对前两种方法减少了人为判断拉力方向或速度带来的误差,使得数据更为稳定可靠。尽管利用测力装置测出的剥皮力能更客观地描述猕猴桃剥皮性状,但是仅凭这一指标也无法比较各个猕猴桃品种剥皮性状的差异。研究结果显示,虽然中华猕猴桃中云海1 号、金奉、万鼎1 号和美味猕猴桃中米良1 号剥皮力也相对较小,但是其剥皮数较多且剥离度评价等级低,果皮与果肉的分离时,果肉受损程度高;而毛花猕猴桃中赣绿1号的剥皮数最少、剥离度评价等级最高并且其所需的剥皮力也较小,更容易剥皮。因此,评价猕猴桃果实的剥皮性状需要综合剥皮数、剥离度和剥皮力3 个指标进行分析比较。

综合剥皮数、剥离度和剥皮力3个指标,表明同一种类不同品种间的猕猴桃果实剥皮性也有较大差异。16 个中华猕猴桃品种中金丰和金奉相对其他品种更易剥皮,果肉受损程度较低;4个美味猕猴桃品种中米良1 号相对其他品种果皮更易剥落,果肉受损程度较低;5 个毛花猕猴桃品种中中华特果皮最厚,果皮剥落顺畅,但所需剥皮力较大,赣绿1 号相对其他品种更易剥皮且不费力,赣猕6 号剥皮次数多相对其他品种较难剥皮。猕猴桃果实剥皮性状受到品种影响,这与前人在猕猴桃上的研究结果也是吻合的[21]。此外,在葡萄[22]、枇杷[7]、柑橘[9]等果实上同样发现果实剥皮性会因品种不同而表现出很大差异,例如有研究发现鲜食葡萄品种中醉金香和白罗莎里奥的果皮与果肉易分离[22];对枇杷剥皮难易程度按难-较易-易三种进行分级,发现有占鉴定总数58.72%的枇杷种质易剥皮,包括其林本、白枇杷皖泊和光荣种等品种[7];有研究发现向山、克里曼丁、药香柑和弗莱特蒙四种宽皮柑橘在成熟过程中剥皮性也存在明显差异,向山最易剥皮[8-9]

目前已有部分关于毛花猕猴桃剥皮性状形成的研究,但大多集中在果皮结构及果皮细胞中果胶物质和半乳糖方面[5,18,23],其分子调控机制尚未明确。对猕猴桃果实剥皮性状进行评价分析,将有助于对毛花猕猴桃果皮结构和剥皮特性形成的相关机制研究。通过本研究建立的猕猴桃果实剥皮性状的综合评价体系,比较分析得出:在易剥皮的毛花猕猴桃种类中,赣绿1 号剥皮数更少、剥离度评价等级更高、剥皮力更小,而赣猕6号剥皮数更多、剥离度评价等级更低、剥皮力更大。因此,笔者课题组将剥皮性相对较差的毛花猕猴桃赣猕6号和剥皮性好的毛花猕猴桃赣绿1号的果皮质地、果皮细胞结构、细胞壁多糖相关物质含量和相关代谢酶活性等进行了分析比较,并结合毛花猕猴桃赣绿1 号果皮转录组和代谢组的检测分析,筛选出了3 个与剥皮性状密切相关的基因[24],为深入解析毛花猕猴桃果实易剥皮特性形成的分子机制奠定了基础。

4 结 论

不同种类的猕猴桃果实软熟期的剥皮性状差异较大,毛花猕猴桃比中华猕猴桃和美味猕猴桃更容易剥皮;同一种类不同猕猴桃品种间的果实软熟期剥皮性也存在差异。本试验基于力学测量装置构建了一个猕猴桃测力装置,通过测定猕猴桃果实软熟时皮肉分离过程中力的大小,并结合剥皮数和剥离度两个指标进行综合评价,结果表明,25 个猕猴桃品种中毛花猕猴桃赣绿1 号最容易剥皮,其性状表现为剥皮数少、剥离度评价等级高并且所需剥皮力也较小。剥皮数、剥离度和剥皮力的综合评价体系的建立,不仅能更加客观地描述猕猴桃果实的剥皮特性,也为后续深入研究猕猴桃剥皮性的生理和分子机制奠定了基础。

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Study on fruit peeling characters of different kiwifruit varieties

HUANG Lihong,WU Mengting,ZHONG Wenqi,TAO Junjie,JIA Huimin,HUANG Chunhui*
(College of Agronomy, Jiangxi Agricultural University/Kiwifruit Institute of Jiangxi Agricultural University, Nanchang 330045, Jiangxi,China)

Abstract: 【Objective】Actinidia chinensis var. chinensis and A. chinensis var. deliciosa are the main types of commercially cultivated kiwifruit at present,the inconvenience of peeling and eating both hinder consumer’s choice of kiwifruit. Some varieties of kiwifruit, such as A. eriantha generally has the characteristics of easy peeling,however,there is no comprehensive and objective evaluation system for the description of the peeling traits of different kiwifruit varieties.In this study,we compared the changes of fruit peeling traits of different kiwifruit varieties at soft ripening stage and established a comprehensive evaluation system of kiwi-fruit peeling traits to objectively reflect the difference of fruit peeling difficulty among different kiwifuit varieties, which would lay a theoretical foundation for further research on the physiology and molecular mechanism of kiwi-fruit peeling.【Methods】Twenty-five kiwifruit varieties were used as materials, including 16 A. chinensis var. chinensis varieties, 4 A. chinensis var.deliciosa varieties,and 5 A.eriantha varieties.The“peeling number”,“peeling degree”and“peeling force”of each kiwifruit variety were tested respectively.The number of peeling refered to the number of skins removed from the whole fruit by manual tearing from the stylar end to the stalk end. The peeling degree was evaluated by assigning scores, which were divided into 5 grades according to peel and pulp peel degree(unable to peel at all,more difficult to peel,difficult to peel,easier to peel,easy to peel). Combined with the kiwifruit stripper based on the mechanical measuring device, the peeling force of each kiwifruit was determined by measuring the force in four directions of the fruit and calculating the average value.Then the evaluation system of kiwifruit peeling traits was established by synthesizing the three indexes,and the differences of peeling traits among different kiwifruit varieties were compared.【Results】The peel number of A. eriantha was significantly less than those of A. chinensis var.chinensis and A.chinensis var.Deliciosa,and the peeling degree evaluation grade was significantly higher than those of the two varieties,indicating that A.eriantha was easier to peel and had better peeling property than the other two kiwifruit varieties.However,the peeling force of A.eriantha was not the smallest, and the peeling power of A. chinensis var. chinensis and A. chinensis var. Deliciosa was even lower than that of A.eriantha.Therefore,by comprehensively comparing the fruit peeling number,peeling degree and peeling force of different varieties of kiwifruit,three indexes were obtained:Among the 16 varieties of A.chinensis with the same fruit size,Jinfeng had less peeling times(18 times)than other varieties, the highest peeling degree was 3-4 points, and the pulp damage degree was lower, followed by Jin Feng, in the case of little difference in peeling number and peeling degree with other varieties,the average peeling force required was 0.42 N,which was the smallest.Among the 4 varieties of A.chinensis var. deliciosa with the same fruit size, Miliang No. 1 had little difference in the peeling number and peeling degree compared with the other varieties, but the average peeling force required was only 0.38 N, the peel was easier to peel, and the pulp was less damaged, although 20 times of the peeling number of Guichang was the least, but the required peeling force was 1.20 N, the peel was also more difficult to peel.Among the 5 varieties of A.eriantha with the same fruit size,Ganlü No.1 had at least 7 peeling times compared with the others, and the highest peeling degree was 7-8 points, and Ganlü 6 had the peeling degree 5-6 points,the highest peeling number(13 times)and was relatively difficult to peel compared with the others.In summary,there were great differences in the peeling traits of different kiwifruit varieties. Among the 25 kiwifruit varieties, Ganlü No. 1 had the lowest peeling number, the highest peeling degree,and the lower peeling force,second only to the lowest Jin Feng and Milang No.1, and it was the easiest to peel according to the evaluation of three indexes. The peeling number of Donghong and Hongshi No.2 was as high as 49 times and 52 times,the peeling degree grade was 0,the average peeling force required was 1.68 N and 1.59 N,significantly higher than those of the other kiwifruit varieties,so both were not easy to peel.【Conclusion】The fruit peeling characters of different kiwifruit species were different.At the same time, different varieties of the same kind of kiwifruit peeling characters also had great differences. By comprehensively comparing the fruit peeling number, peeling degree and peeling force of each variety of kiwifruit,among the 25 kiwifruit varieties,Ganlü No.1 had the lowest peeling number, the highest peeling degree evaluation grade, and the smallest peeling force,so it was the easiest to peel.

Key words: Kiwifruit;Fruit;Peeling character;Peeling number;Peeling force

中图分类号:S663.4

文献标志码:A

文章编号:1009-9980(2024)12-2463-09

DOI: 10.13925/j.cnki.gsxb.20240402

收稿日期:2024-08-19

接受日期:2024-09-14

基金项目:国家自然科学基金项目(31960588);江西省现代农业产业技术体系建设专项(JXARS-05)

作者简介:黄丽红,女,在读硕士研究生,研究方向为果树种质资源与分子生物技术。E-mail:2330618272@qq.com

*通信作者 Author for correspondence.E-mail:lindahch@126.com