西番莲果皮质构特性和显微结构特征分析

Analysis of texture characteristics and microstructure of passion fruit pericarp

【目的】筛选适合西番莲果皮质构特性的测试方法,综合评价西番莲的果皮质构特性与果皮显微结构的相关性,为提高西番莲果实耐贮性及改良种质资源提供参考。【方法】以台农1号(TN)及编号为MB、H2、DH、ZS的5个西番莲品种(系)的成熟果实为试验材料,分别采用质地剖面分析(TPA)和整果穿刺(分别设置穿刺深度为5 mm和10 mm)进行果皮质构分析,同时观察果皮显微结构,并对果皮质构特性和显微结构参数进行相关性分析。【结果】(1)TPA测试与穿刺测试的果皮硬度趋势不一致,而穿刺5 mm和穿刺10 mm测试多项结果一致,相关分析显示TPA测试与穿刺测试的质构指标间无显著相关性。(2)穿刺测试下的各项质构参数间存在显著相关性,穿刺硬度、硬度形变量、穿刺果皮做功、黏力和黏性均可以作为西番莲果皮质地的参数。(3)西番莲的果皮主要由外果皮和中果皮组成,外果皮由外向内结构依次为角质层、表皮细胞和内表皮细胞;中果皮细胞由外向内呈现形态逐渐增大的趋势,是构成西番莲果皮结构的最主要部分。(4)相关分析显示果皮厚度与TPA硬度、胶着性、咀嚼性和穿刺硬度均呈极显著正相关;角质层厚度与TPA硬度和胶着性呈显著正相关,而与内聚性呈极显著负相关;距离外果皮400~1000μm和1500~2300μm的中果皮细胞长径和短径、表皮细胞短径与硬度形变量均呈极显著负相关,而与黏力和黏性均呈极显著正相关。(5)5个西番莲品种(系)中TN的果皮角质层和果皮厚度最小,中果皮细胞大而稀疏,致使其果皮硬度最小;H2的中果皮细胞小而紧密,使其有较大的果皮硬度;DH和ZS的果皮最厚,ZS角质层最厚,更耐贮运,而MB的外果皮最薄。【结论】整果穿刺测试较TPA测试更适合西番莲果皮质构特性分析;西番莲果皮质构特性与果皮显微结构具有显著相关性,果皮硬度较大的西番莲果皮组织结构特点为角质层、表皮、果皮厚度较大且中果皮细胞小而排列紧密。

【Objective】In this study,we compared the pericarp texture characteristics of passion fruit by means of the texture profile analysis(TPA)and whole fruit puncture test to screen out suitable test methods for the texture characteristics of passion fruit.Combined with the observation results of pericarp microstructure,the correlation was comprehensively evaluated between the pericarp texture characteristics and the pericarp microstructure,so as to provide reference for improving the storage resistance and germplasm resources of passion fruit.【Methods】In this study,the mature fruits of Tainong 1(TN)and five passion fruit varieties(lines)coded as MB,H2,DH and ZS were used as experimental materials.Three kinds of pericarp texture analysis test modes were set up in the experiment:TPA,whole fruit puncture(puncture depth of 5 mm)and whole fruit puncture(puncture depth of 10 mm).Among them,TPA test required sample pre-treatment,and pericarps of 1.5 cm×1.5 cm square size on both sides of the central line were cut for testing.The puncture test samples were complete fruits,and the puncture site was along the central line of the horizontal axis of the fruit.In addition,we made paraffin sections of the pericarp and observed the microstructure of the longitudinal section of the pericarp.We also analyzed the correlation between pericarp texture characteristics and microstructure parameters.【Results】(1)The pericarp hardness trend of TPA test was not consistent with that of puncture test,while puncture 5 mm test and puncture 10 mm test had many consistent results.In addition,correlation analysis showed that there were no significant correlations in texture indexes between TPA test and puncture test.We speculated that the consistency of sample size could not be accurately controlled when the fruit pericarp samples were cut,and it was found in the test that the passion fruit pericarps were not completely flat and fitted to the test table,so the TPA test results would be affected.Therefore,we judged that puncture test was more suitable for texture analysis of passion fruit pericarp.(2)In puncture test mode(puncture depth of 10 mm),the results showed that there were significant correlations among texture parameters:pericarp hardness was significantly and extremely significantly positively correlated with deformation and pericarp puncture work;deformation was significantly and positively correlated with pericarp puncture work;adhesive force was significantly and positively correlated with adhesiveness.Therefore,puncture hardness,deformation,pericarp puncture work,adhesive force and adhesiveness can all be used as the parameters to reflect the texture of passion fruit pericarp.(3)The pericarp of passion fruit was mainly composed of exocarp and mesocarp.The exocarp was composed of cuticle,epidermal cells and inner epidermal cells from outside to inside.The thickness of the outermost cuticle was about 2.5-5.0μm.There were 1-4 layers of epidermal cells,which were closely arranged rectangular cells with the ratio of length to diameter by 1.15-1.65.There were 1-4 layers of inner epidermal cells,which were colorless and transparent,and were larger than the epidermal cells.Mesocarp cells gradually increased in shape from outside to inside,and the cell transition was from tight to sparse arrangement.Mesocarp was the most important part of passion fruit pericarp structure.(4)The correlation analysis of texture parameters and microstructure parameters of pericarp showed that there were significant and positive correlations between pericarp thickness and TPA hardness,gumminess,chewiness and puncture hardness.The thickness of cuticle was positively correlated with TPA hardness and gumminess,but negatively correlated with cohesiveness.Furthermore,the long and short diameters of mesocarp cells were 400-1000μm and 1500-2300μm away from exocarp,the short diameter of epidermal cells was significantly and negatively correlated with deformation,but significantly and positively correlated with adhesive force and adhesiveness.These results suggested that the relatively elongated epidermal cell morphology and the mesocele structure with compact arrangement of small cells were more conducive to improving the deformation and reducing the adhesive force and adhesiveness.(5)Among the 5 passion fruit varieties(lines),TN had the smallest cuticle and pericarp thickness,and its mesocarp cells were large and sparse,resulting in the lowest pericarp hardness.In contrast,the mesocarp cells of H2 were small and compact,giving it greater pericarp hardness.Besides,DH and ZS had the thickest pericarp,and ZS had the thickest cuticle and was more resistant to storage and transportation,while MB had the thinnest exocarp,and its thickness of cuticle,epidermal and pericarp was small.【Conclusion】Compared with TPA test,whole fruit puncture test was more suitable for analyzing the texture of passion fruit pericarp,the puncture depth can be set to 10 mm.There was a significant correlation between the texture and microstructure of passion fruit pericarp.According to this study,it can be concluded that the hard pericarp of passion fruit is characterized as large thickness of cuticle,epidermis and pericarp,and small and tight mesocarp cells.