摘要
【目的】明确西洋梨果实后熟过程中生理生化变化规律及各生理指标间的相关性,找到反映果实后熟进程的特征指标,实现西洋梨果实后熟程度的快速无损检测。【方法】以‘三季梨’果实为试材,比较果实不同后熟时间的生理生化指标,并进行各生理指标间的相关性分析。【结果】在‘三季梨’果实后熟过程中,果皮色泽由绿转黄,亮度逐渐增加;叶绿素光化学效率(F_v/F_m)前6 d无明显变化,后2 d迅速下降,叶绿素a、叶绿素b及总叶绿素含量呈下降趋势;硬度、可滴定酸含量、维生素C含量呈逐渐下降趋势,可溶性固形物含量呈先增加后下降趋势;淀粉指数(SI)升高,酶含量降低,后熟6 d时出现乙烯和呼吸跃变峰。果实的后熟软化伴随着果皮叶绿素含量、h°值和叶绿素荧光参数中的F_0、F_v等指标的下降。通过相关性分析表明,果实硬度分别与叶绿素a、叶绿素b、总叶绿素含量、h°值、F_m和F_v等表征果皮颜色的指标以及与淀粉含量、纤维素酶活性等软化指标呈极显著正相关,与F_0和F_v/F_m呈显著正相关。同时发现,果皮颜色h°值与叶绿素a、叶绿素b、总叶绿素、叶绿素荧光参数F_0、F_v、F_m和F_v/F_m呈极显著正相关,与L*、a*、b*呈极显著负相关。【结论】西洋梨果实后熟主要是由于淀粉含量下降、纤维素酶活性变化引起果实硬度下降以及果皮叶绿素降解导致果面由绿转黄,最终完成果肉软化、果皮转黄的后熟过程。另外,以硬度下降至3 kg·cm^(-2)时作为果实最佳食用期,后熟过程中可通过果皮颜色或叶绿素荧光参数来对果实最佳食用期进行无损判断,当测定h°值低于105或L*值高于70时,或F_v/F_m低于0.7时,果实达到最佳食用期。
【Objective】‘Docteur Jules Guyot＇, a representative European pear（Pyrus communis L.） cultivar was used in this study to investigate the changes in various physiological and biochemical indexes and analyze their correlations during the postharvest ripening of European pear.【Methods】Loss of fruit firmness is an obvious change in the after ripening of‘Docteur Jules Guyot＇pear. Fruit were transported to the laboratory and precooled at（0±0.5） ℃ for 24 h. Uniform sized fruit without lesions were selected as the materials. The precooled fruit were packed with PE bags（the thickness： 0.02 mm） and stored at room temperature（20±1 ℃）. The fruit in the bags were sampled every day until the fruit firm-ness reduced to 2.0 kg · cm^-2. Three biological replicates were performed each with 10 fruit. Chromatic aberration, chlorophyll fluorescence, soluble solids, titratable acid content, vitamin C content, pulp firmness, fruit respiration intensity, ethylene release, starch staining, starch content and various enzymes were measured for investigating the physiological and biochemical changes.【Results】During the storage of‘Docteur Jules Guyot＇fruit, the skin color changed from green to yellow, with L＊value increasing gradually. Photochemical efficiency（Fv/Fm ） showed no significant change in the first 6 d but decreased rapidly later, and the contents of chlorophyll a, chlorophyll b and total chlorophylls decreased with the after-ripening and softening of the fruit. h° value of the‘Docteur Jules Guyot＇declined with the prolongation of storage time at room temperature. When the firmness reduced to 1.64 kg · cm^-2（less than 2.0 kg · cm^-2）, h° value was 95.50 and the peel turned completely yellow. Chlorophyll fluorescence detection indicated that chlorophylls were activated by light. With the ripening of‘Docteur Jules Guyot＇at room temperature, Fv/Fm declined continuously, and the lowest value of 0.3 appeared at the 8 th day. The coordinated changes in chlorophyll content and fruit color suggested that a high content of soluble sugar played an important role in the regulation of chloroplast thylakol disintegration and chlorophyll degradation. In this experiment, the chlorophyll content showed continuous decline with storage time. There was a significant negative linear correlation between starch dyeing index and fruit firmness（r = 0.92＊＊）. In this study, we found that the amylum content decreased with storage time from 44.91 mg · g^-1 to 24.89 mg · g^-1. Amylase activity increased at the beginning and then decreased, and reached its maximum value of 6.60 mg· g^-1· min^-1 at the 4 thday. The cellulase activity decreased gradually, and the cellulase activity decreased rapidly from harvest to day 5, after which, the cellulase activity decreased to the lowest value of 0.36 μ g· g^-1· h^-1 and maintained this low value thereafter. Polygalacturonase（PG）activity was 1.31 μg· g^-1·h^-1 at the 5 thday, and then decreased to its lowest value of 0.67 μg· g^-1·h^-1. The content of soluble sugars increased continuously, and in contrast, titratable acid content decreased continuously. Vitamin C content decreased slowly to 2.30 mg · 100 g^-1. The values of respiratory intensity and ethylene release both reached their highest values on the 6^th day, which were 155.76 μL· kg^-1·h^-1 and 91.14 mg · kg^-1·h^-1, respectively.【Conclusion】During the after-ripening of European pear fruit, starch content and firmness of fruit decreased gradually and the skin color changed from green to yellow. Fruit with a firmness of 3.0 kg· cm^-2 had the best taste. During the after-ripening and softening of the fruit, the skin color and chlorophyll fluorescence parameters could be used as the standards for judging the fruit status with the best taste. In the case of‘Docteur Jules Guyot＇, the best eating quality was attained when fruit h° value was below 105, L＊value above 70 and Fv/Fm below 0.7.
作者
马风丽
贾晓辉
王志华
李艳
杜艳民
佟伟
孙平平
崔建潮
王阳
王文辉
MA Fengli;JIA Xiaohui;WANG Zhihua;LI Yan;DU Yanmin;TONG Wei;SUN Pingping;CUI Jianchao;WANG Yang;WANG Wenhui(Research Institute of Pomology, Chinese Academy of Agricultural Sciences, Xingcheng 125100, Liaoning, China;Beijing Daring District Landscaping Bureau, Beijing 102600, China)
出处
《果树学报》
CAS
CSCD
北大核心
2018年第6期718-728,共11页
Journal of Fruit Science
基金
国家重点研发计划项目(2016YFD0400903-06)
国家现代农业产业技术体系建设专项(CARS-29-19)
中国农业科学院科技创新工程(CAAS-ASTIP)
关键词
'三季梨’
后熟
果皮颜色
生理生化
相关性
‘Docteur Jules Guyot＇
Ripening
Physiological and biochemical changes
Correlation
作者简介
马风丽，女，在读硕士研究生，主要从事果实品质生理研究。Tel：15533816736，E-mail：2689466330@qq．com;通信作者．Tel：0429—3598188，E-mail：wangwenhui@caas．cn
