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Article

Textural Characteristics and Anatomical Structure of Hard- and Soft-Fleshed Jujube Fruits

by
Xiaodong Zhang
1,2,†,
Min Yan
2,†,
Yongle Sun
1,
Xiaofeng Zhou
1,2,
Ze Yuan
1,
Xiangyu Li
1,2,
Minjuan Lin
1,2 and
Cuiyun Wu
1,2,*
1
National-Local Joint Engineering Laboratory of High Efficiency and Superior-Quality Cultivation and Fruit Deep Processing Technology on Characteristic Fruit Trees/Technology Innovation Center for Characteristic Forest Fruits in Southern Xinjiang, Alar 843300, China
2
Corps Key Laboratory of Conservation and Utilization of Biological Resources in Tarim Basin, Alar 843300, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Agriculture 2024, 14(12), 2304; https://doi.org/10.3390/agriculture14122304
Submission received: 21 October 2024 / Revised: 6 December 2024 / Accepted: 14 December 2024 / Published: 16 December 2024
(This article belongs to the Special Issue Fruit Quality Formation and Regulation in Fruit Trees)
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Versions Notes

Abstract

:
The aim of this study was to establish a standardized and unified method for identifying and evaluating jujube fruit texture quality and to provide a theoretical basis for determining the texture quality of jujube germplasm resources. The texture of 56 jujube germplasms was characterized via the texture profile analysis (TPA) method, and the texture and anatomical structure of three each of the hard- and soft-fleshed germplasms were analyzed. Cluster analysis was used to categorize the 56 germplasms into hard- (17) and soft-fleshed jujubes (39). Significant positive correlations were found between all other textural parameters of jujube fruits except adhesiveness. The hardness, springiness, and chewiness of the full-red period hard- and the soft-fleshed jujube fruit were lower than those of the half-red period. The hardness, adhesiveness, and chewiness of the hard-fleshed jujube fruits in the full-red period were 2.13–3.57, 3.00–4.99, and 4.39–9.58 times higher than those of the soft-fleshed jujube fruits, respectively. The findings of this study provide a theoretical foundation for the evaluation and classification of the texture and quality of jujube fruits and a basis for the breeding of new, high-quality jujube varieties with distinctive characteristics.

1. Introduction

The Chinese jujube (Ziziphus jujuba Mill.) is one of the most widely cultivated and economically important tree species in the Rhamnaceae family. Jujube fruit is rich in nutrients, has a unique flavor with a variety of textures and uses, and can be eaten fresh or processed into dried jujube slices, jujube wine, jujube vinegar, etc., which are popular with consumers [1]. Characterizing the texture of food involves evaluating a combination of its properties felt through the mouth, teeth, tongue, and mucous membranes, mainly providing a description of the density, looseness, crunchy, and juiciness of the flesh of fruit [2]. In addition to appearance and flavor, texture is one of the key attributes affecting the quality of jujube fruits and consumer preference. Fruit texture also has a significant effect on fruit transportation, storage freshness, and shelf life [3]. Fresh jujubes are usually picked early (fruit color change period) to maintain fruit hardness and to reduce mechanical damage and the effects of disease during production, thus maximizing storage and transportation time. However, consumers are dissatisfied with the taste and flavor of early-picked fruit. If harvested at optimal ripeness (full-red period), jujube fruit has its typical flavor and textural qualities that meet consumer expectations, so consumption increases. As such, the study of the mechanisms underlying the textural differences in jujube fruits may provide a theoretical basis for breeding efforts to increase fruit quality.
Fruit texture can generally be classified into three types: hard, crunchy, and soft [4,5,6]. Compared with the traditional sensory evaluation of texture, evaluating fruit and vegetable texture using a meter provides large amounts of information and is fast, so it is being increasingly used. Studies have focused on the relationship between texture meter evaluation and sensory evaluation indices for different fruits and vegetables [7,8,9]. The higher the index, such as the juice yield or pomaceability index, the finer the texture of the fruit and the better the taste [10]. A comparison of the texture of different taxa of fruit revealed that taxa with high cohesiveness, high adhesiveness, and softer texture had a lower rupture force and a softer texture. The crunchier the fruit texture, the higher the soluble protein content of the skin and pulp [11]. The texture of pear [12], apple [13], and grape [14] during development and ripening has been extensively studied. The biochemical characteristics of the various fruit developmental stages are important factors influencing fruit texture characterization [15]. The internal quality indicators of fruit, such as soluble solid content [4,16], titratable acid content [17], and soluble sugar content [18], also influence its texture. Changes in fruit texture are also closely related to cell morphology, expansion pressure, and cell wall structure [19]. Hard fruit usually has tightly arranged pulp cells with thicker and more structurally intact cell walls, brittle fruit has more tightly arranged cells but thin cell walls and larger pulp cells, and tough fruit has a high number of pulp cells with small individual cells and thin cell walls [20]. High concentrations of stone cells elevate the roughness of the texture of pear flesh [21]. The orderly arrangement of regular-shaped cells and loosely arranged irregular-shaped cells are responsible for crunchy and powdery melon textures, respectively [22]. Therefore, comparing the differences in textural characteristics and anatomical structure of the flesh of jujube fruits is important for exploring the key factors determining the formation of their textures and increasing their textural quality.
Fruit texture widely differs among the different jujube germplasms. Yet, the mechanisms responsible for the differences in fruit texture among different types of jujubes are not well understood. Most of the current studies have focused on postharvest softening of jujube fruits, with fewer studies on the different textures of jujube fruits. Therefore, analyzing the textural diversity of jujube germplasm and exploring the differences in the textural characteristics and anatomical structure of different jujube fruits are theoretically important for understanding the mechanism through which jujube fruit ripening and softening is regulated to enable a further genetic increase in the overall quality of jujube fruits. In this study, we determined the fruit texture of 56 jujube germplasms and examined the textural characteristics and microstructural differences among different types of jujube fruits. Our aim was to provide a theoretical basis for the establishment of a jujube fruit texture evaluation system and for the selection of high-quality jujube varieties for breeding, thus providing guidance and data for further analyzing the mechanism through which the textural characteristics of jujube fruits are formed.

2. Materials and Methods

2.1. Overview of Study Area

This study was conducted at the Live Jujube Progeny Selection Nursery of Tarim University, Alar, Xinjiang. It was located at 40°32′50′′ N and l 81°17′12′′ E, with an average altitude of 999 m. The area was characterized by a warm temperate and extreme continental arid desert climate, precipitation was scarce, and light hours were long. The average annual temperature was 12.3 °C, the frost-free period was 220 days, the average annual sunshine hours ranged from 2556.3 to 2991.8 h, the average annual precipitation was 40.1~82.5 mm, and the soil was light salinized soil.

2.2. Plant Materials

Fifty-six germplasms (live progeny monocots) from the Live Jujube Progeny Selection Nursery of Tarim University were used as the test materials. The germplasms were 9 years old, with the main stem shaped in a tree form, 1.5 m × 2 m spacing between rows and plants, and consistent management practices. In 2023, a total of 30 fruits were randomly selected from each germplasm during the full-red period (with fully red peel and no softening [23]) of fruiting. They come from different directions on the tree, and they have a consistent fruit size and maturity. We immediately brought the samples back to the lab and completed the textural characterization within 6 h. The 56 germplasms were classified into two categories according to the results of the cluster analysis of their textural characteristics: hard- and soft-fleshed jujube fruits.
In conjunction with the taste evaluation, three germplasms each of the hard-fleshed jujube fruits (2-11-10, 1-10-20, and 2-12-17) and soft-fleshed jujube fruits (2-6-5, 2-7-5, and 2-10-22) were selected and sampled at the half-red period (about 40–60% red peel [23]) and full-red period to determine the fruit quality, textural characteristics, and anatomical structure of the fruits. For fruit sampling, a total of 60 fruits were selected from each germplasm. They came from four directions in the middle of the canopy, east, west, south, and north. Ten fruits were randomly selected from each of the 60 fruits of each germplasm and sampled immediately for anatomical structure. The remaining 50 fruits were stored at low temperatures (temperature 4 °C, humidity 85–90%), and 30 fruits were randomly selected for textural characterization (completed within 6 h after picking) after the determination of fruit appearance quality was completed. The remaining 20 fruits were subsequently pitted, chopped, and mixed and stored in a refrigerator at −20 °C to determine the intrinsic quality of the fruits.

2.3. Test Methods

2.3.1. Determination of Physical Attributes of Jujube Fruit

Single fruits were weighed using an FA 1104 N electronic balance (Shanghai Pohai Instrument Company, Shanghai, China); the longitudinal and transverse diameters of the fruits were measured using Vernier calipers (Shanghai Deyixing Tools Co., LTD., Shanghai, China).

2.3.2. Determination of the Intrinsic Quality Parameters of Jujube Fruit

The soluble solid content was determined using a PAL-1 digital handheld pocket refractometer (ATAGO Co., Ltd., Tokyo, Japan). The determination of vitamin C content was conducted using the molybdenum blue colorimetric method [24]. Soluble sugar content was quantified through anthrone colorimetry [25]. Titratable acid content was determined via an acid–base neutralization method [26].

2.3.3. Determination of Textural Characteristics of Jujube Fruit

We used a TMS-Pro high-precision professional food property analyzer (Ensoul Technology LTD, Beijing, China) to determine the texture of the jujube fruits. The parameters were set to a maximum of 500 N, a lift height of 60 mm, a deformation of 10%, and a detection speed of 60 mm/min. Intact jujube fruits were placed on a tray to determine six TPA texture parameters, hardness, adhesiveness, cohesiveness, springiness, gumminess, and chewiness, according to the previously reported method [27], for the sensory definition of textural characterization indicators.

2.3.4. Determination of Anatomical Structure of Jujube Fruit

The jujube fruits were cut into small rectangular pieces, 0.5 cm long and wide, along the central equatorial line. The samples were placed in Formalin-Aceto-Alcohol (FAA) fixative for more than 24 h. After gradient ethanol dehydration to transparency, the samples were embedded in paraffin wax to completely solidify and then sliced with a YD-335 slicer (Jinhua YIDI Medical Appliance CO., LTD, Jinhua, China) into 8 μm sections. The sections were dried completely and dewaxed with xylene. The sections were stained and sealed with Arabic gum; an OLYMPUS fluorescence microscope was used to observe and measure epidermal cell thickness and thin-walled cell width, length, and area. Twenty fields of view per sample were observed, recorded, and averaged.

2.4. Data Processing and Analysis

All results were expressed as mean ± standard error. Duncan’s multiple comparison test and analysis of variance were performed using IBM SPSS Statistics version 26.0 (IBM, Armonk, NY, USA). The significance level was set to p < 0.05. The jujube pulp tissue section images were analyzed using OLYMPUS-cellsens standard software version 2.1 (Build 17342) to obtain epidermal cell thickness as well as thin-walled cell width, length, and area cytomorphological parameters. Cluster analysis, correlation analysis, and mapping were conducted with Chiplot (https://www.chiplot.online/) URL (accessed on 12 August 2024). Principal component analysis and plotting were performed with Origin 2021 (Origin Lab Inc., Northampton, MA, USA).

3. Results

3.1. Textural Characteristics of 56 Jujube Germplasms

The 56 germplasms were classified into two categories according to the results of the systematic cluster and correlation analyses of the standardized textural characteristic indices of the full-red fruits (Figure 1). Group I contained 17 germplasms, accounting for 30.36% of the total, e.g., 2-11-19, V1-1-17, and 2-3-6, which were characterized by higher fruit hardness, springiness, and chewiness. The mean fruit hardness, springiness, gumminess, and chewiness were 245.07 N, 3.51 mm, 101.89 N, and 370.68 MJ, respectively (Figure 2). Group II contained 39 germplasms, accounting for 69.24% of the total, e.g., 2-9-18, 2-6-5, and 2-10-9, which were characterized by lower fruit hardness, springiness, chewiness, and relatively loose and soft jujube flesh. The mean fruit hardness, springiness, gumminess, and chewiness in this group were 165.48 N, 2.40 mm, 47.64 N, and 124.18 MJ, respectively (Figure 2). We found no significant differences in the cohesiveness or adhesiveness of the germplasms between the two groups. The results of correlation analysis revealed significant positive correlations among the textural parameters, such as the hardness, cohesiveness, springiness, adhesiveness, and chewiness of the jujube fruits, with adhesiveness being significantly positively correlated with springiness (0.29) and significantly negatively correlated with cohesiveness (−0.39).

3.2. Analysis of Characteristics of the Different-Textured Jujube Fruits

The textural characteristics of the hard-fleshed (2-11-10, 1-10-20, and 2-12-17) and soft-fleshed (2-6-5, 2-7-5, and 2-10-22) jujube germplasms were analyzed, and the results are shown in Figure 3. The hardness, gumminess, and chewiness of the hard-fleshed jujube fruits were significantly higher than those of the soft-fleshed jujube fruits at the half-red and full-red periods, being 1.78–2.81, 2.48–3.62, and 2.62–7.66 times higher than those of the soft-fleshed jujube fruits and 2.13–3.57, 3.00–4.99, and 4.39–9.58 times higher than those of soft-fleshed jujube fruits, respectively. Soft-fleshed jujube fruits 2-6-5 and 2-7-5 had significantly lower cohesiveness than the other germplasms. The hardness, springiness, and chewiness of the full-red hard- and soft-fleshed jujube fruit were lower than those of the half-red fruits.

3.3. Analysis of External and Internal Quality of Different-Textured Jujube Fruits

The external and internal qualities of hard- and soft-fleshed jujube fruits were analyzed, and the results are shown in Figure 4. All germplasms had a higher single-fruit weight, longitudinal fruit diameter, transverse fruit diameter, soluble solid content, titratable acid content, and soluble sugar content in the full-red period than in the half-red period. Vitamin C content was lower in the full-red than in the half-red period. Hard-fleshed jujube fruit 1-10-20 had a significantly higher single-fruit weight and fruit transverse diameter than the other germplasms. Soft-fleshed jujube fruit 2-6-5 had the lowest weight per fruit, and 2-7-5 had a significantly lower vitamin C content than all the other germplasms. During the full-red period, hard-fleshed jujube fruit 1-10-20 had the highest soluble solid and vitamin C contents, at 32.17% and 468.04 mg/100 g, respectively.

3.4. Analysis of the Anatomical Structure of Different-Textured Jujube Fruits

The jujube fruit is a drupe, which consists of an exocarp, a mesocarp, and a pome. The exocarp consists of a cuticle, epidermal cells, and subepidermal cells from the outside to the inside; the mesocarp, which is the main edible part of the jujube fruit, mainly consists of thin-walled cells and vascular bundles [28]. The anatomical structures of hard-fleshed (2-11-10, 1-10-20, and 2-12-17) and soft-fleshed (2-6-5, 2-7-5, and 2-10-22) jujube fruits were observed (Figure 5) and analyzed (Figure 6). The thin-walled cells of the jujube fruits all showed irregular polygonal shapes, which were more uniformly and closely arranged in the half-red period; in the full-red period, the thin-walled cells were loosely arranged and larger. The thin-walled cell length, width, and area and pericarp thickness were larger in the full-red period than in the half-red period. Significant differences were found in the cellular anatomical structure of the jujube fruits of different textures: hard-fleshed jujube fruit pulp cells were orderly arranged and regular in shape, whereas soft-fleshed jujube fruits had loosely arranged thin-walled cells of uneven sizes, and more cellular cavities appeared in the pulp cells. In the soft-fleshed jujube fruits, the thin-walled cell length and area and pericarp thickness of 2-7-5 were significantly larger than those of the other germplasms. The pericarp of 2-6-5 showed severe cracks, and the cuticle was almost incoherent (Figure 5d,j), whereas we found no severe cracks in the remaining germplasms.

3.5. Principal Component Analysis of Jujube Fruits

The standardized textural, appearance quality, intrinsic quality, and anatomical structure indices of six hard- and soft-fleshed jujube fruits were subjected to principal component analysis, with the results shown in Figure 7. The contributions of the first three components to the variation in the indices were 52.90%, 16.60%, and 14.90%, respectively, for a cumulative contribution to the total variance of 84.40%. Therefore, the three extracted components were used as a comprehensive evaluation index of the quality of jujube fruits with different textures. In PC1, hardness, springiness, gumminess, and chewiness had high loadings and strong correlations, with all being positive in the same direction, thus indicating positive synergistic effects. We named these fruit texture factors because they are all indicators of textural characteristics. In PC2, the soluble solid and soluble sugar contents had high loadings, which we referred to as intrinsic fruit quality factors. PC2 is the second determinant used to evaluate fruit quality. In PC3, the cell width, length, and area had high loadings, so they were referred to as fruit cell size factors. The high PC1 (fruit texture factor) scores of 1-10-20 and 2-12-17 indicated that the hardness, springiness, gumminess, and chewiness of the hard-fleshed jujube fruits were high. Sample 2-7-5 had a low PC1 score but the highest PC3 (fruit cell size factor) score, indicating that 2-7-5 fruits were softer and had the largest fruit cells.

4. Discussion

The textural fruit characteristics vary considerably among jujube germplasms. Cluster analysis can be used to handle large amounts of data and observe the degree of similarity between different varieties for grading quality and classifying traits [29]. Cluster analysis has been used in the comprehensive quality evaluation and varietal genealogy delineation of pomegranate [30], plum [31], and pear [32]. Few studies have been conducted on the textural characteristics and classification of jujube germplasms using the TPA method. In this study, jujube germplasms were classified into hard- and soft-fleshed jujube fruit using systematic cluster analysis.
We found different degrees of correlations among the standardized textural characteristic indices of the full-red fruits of the 56 germplasms, with significant positive correlations among the textural parameters such as jujube fruit hardness, cohesiveness, springiness, gumminess, and chewiness. Adhesiveness indicates the work performed by a probe to disengage the fruit and the energy required to overcome the attraction between the surface of the fruit and the surface of the tooth of the probe during contact. Jujube has a fleshy fruit pulp that is dense and firm, with a high sugar content and less juice, so the probe work required is low, resulting in a high adhesiveness index accuracy. We found a significant positive correlation between jujube fruit adhesiveness and springiness, a significant negative correlation with cohesiveness (−0.39), and no significant correlations among the other indicators. In previous studies on jujube texture [33,34], the cohesiveness of jujube fruits significantly negatively correlated with adhesiveness, a finding consistent with that in the present study. The cohesiveness of jujube fruits was highly significantly and negatively correlated with hardness, a finding different from that in the present study. We hypothesized that this difference might be due to the differences in the contents of substances within the jujube fruits with different textures, which might have affected the results of the TPA analyses. Another study showed that changes in the anatomical structure of jujube pulp cells were related to the concentrations of fiber and sugars (sucrose and reducing sugars) [18]. In this study, soft-fleshed jujube fruit 2-7-5 had significantly lower vitamin C content than the other germplasms, and the hard-fleshed jujube fruits had overall higher vitamin C contents than the soft-fleshed jujube fruits during the full-red period. We hypothesized that a correlation may exist between vitamin C content and fruit texture.
The arrangement, size, and distribution of plant cells and the cell wall thickness are inextricably linked to fruit texture [35]. In grapes, the larger and more sparsely arranged the cells, the softer the fruit pulp texture [36]. In this study, hard-fleshed jujube fruits exhibited thin-walled cells in the pulp with a smaller area, had a tight arrangement, small cell gaps, and few small cavities; soft-fleshed jujube fruits had thin-walled cells with a larger area, lax arrangement, large cell gaps, and many large cavities, which is basically consistent with the results of a previous study [37]. The hardness of both hard- and soft-fleshed jujube fruits was lower in the full-red period than in the half-red period, which is similar to the findings of a previous study [38]. In this study, the soft-fleshed jujube fruits 2-6-5 and 2-7-5 were softer, but the fruit cell area was the largest among the tested germplasms. This indicates that fruit cell size is one of the key factors affecting fruit texture quality.
The principal component analysis method can be used to simplify and analyze multiple trait indices and to select the key indices from among multiple indices in performing comprehensive evaluations. As such, principal component analysis is widely used in the evaluation of the fruit quality of germplasm resources [39]. The results of the principal component analysis of 10 indicators from 20 peach varieties showed that the chemical composition of fruits substantially varied [40]. The results of the principal component analysis of pears showed that the effect of different Melatonin (MT) concentrations on the increase in pear fruit quality widely varied [41]. In this study, six textural indices, three appearance quality indices, four intrinsic quality indices, and four anatomical structure indices were subjected to principal component analysis, and three factors were retained, with a cumulative contribution of 84.4% to the overall variance in quality. Hardness, springiness, gumminess, and chewiness were more influential, as seen in PC1, and a strong link was identified from the correlation analysis. From the results of the principal component analysis, the influence of each factor on jujube quality was ranked as follows: fruit texture factors > fruit intrinsic quality factors > fruit cell size factors.

5. Conclusions

In this study, the 56 tested germplasms were categorized into two groups of hard-fleshed jujube fruits and soft-fleshed jujube fruits, and the main difference between these two groups was the obvious difference in hardness and springiness. The high hardness and high springiness group (Group I) is suitable for use as fresh jujube or dried jujube fruit, while the low hardness and low springiness group (Group II) jujube fruits are suitable for use in the production of a variety of processed foods, such as jujube powder, jujube wine, and so on. Significant positive correlations were found between all other textural parameters of jujube fruits except adhesiveness. Fruit hardness, springiness, and chewiness can be used as key indicators to evaluate the textural quality of jujube fruits. In summary, our results provide a theoretical basis for the evaluation and classification of jujube fruit texture quality and for further selection and breeding of new varieties of high-quality jujube with special characteristics.

Author Contributions

X.Z. (Xiaodong Zhang) and M.Y. designed the study, obtained data, performed statistical analyses, wrote the manuscript, and interpreted the data. C.W. revised and reviewed this article. Y.S., X.Z. (Xiaofeng Zhou), Z.Y., X.L. and M.L. participated in the conception and design of the study, interpreted the data, and reviewed and edited the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This study was funded by the Key Industry Support Plan Project of Xinjiang Jujube Industrial Technology System (No. XJCYTX-01-01-2024); the Technological Project ‘Selection and breeding of new varieties of early maturing, high-quality, large-fruited, and easy-to-yield fresh jujube’ (2024AB021); and the Tarim University Innovative Research Team Program (2023ZD104).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The original contributions presented in this paper are included in this article; further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Textural characteristics of 56 jujube germplasms. (a) Cluster and (b) correlation analyses of textural characteristics of 56 jujube germplasms. * indicates a significant difference (p < 0.05), and ** indicates a very signi ficant difference (p < 0.01) by t-test, the same below.
Figure 1. Textural characteristics of 56 jujube germplasms. (a) Cluster and (b) correlation analyses of textural characteristics of 56 jujube germplasms. * indicates a significant difference (p < 0.05), and ** indicates a very signi ficant difference (p < 0.01) by t-test, the same below.
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Figure 2. Textural characteristics of various groups of jujube germplasms: (a) hardness; (b) adhesiveness; (c) cohesiveness; (d) springiness; (e) gumminess; (f) chewiness. The dots in the figure indicate the mean value of each germplasm in the group.
Figure 2. Textural characteristics of various groups of jujube germplasms: (a) hardness; (b) adhesiveness; (c) cohesiveness; (d) springiness; (e) gumminess; (f) chewiness. The dots in the figure indicate the mean value of each germplasm in the group.
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Figure 3. Textural characteristics of different-textured jujube fruits: (a) morphology of jujube fruits with different textures; (b) hardness; (c) adhesiveness; (d) cohesiveness; (e) springiness; (f) gumminess; (g) chewiness. Different lowercase letters in the figure indicate significant (p < 0.05) differences between germplasm under the same period.
Figure 3. Textural characteristics of different-textured jujube fruits: (a) morphology of jujube fruits with different textures; (b) hardness; (c) adhesiveness; (d) cohesiveness; (e) springiness; (f) gumminess; (g) chewiness. Different lowercase letters in the figure indicate significant (p < 0.05) differences between germplasm under the same period.
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Figure 4. External and internal qualities of different-textured jujube fruits: (a) single-fruit weight; (b) longitudinal diameter; (c) transverse diameter; (d) soluble solid; (e) vitamin C; (f) titratable acid; (g) soluble sugar contents. Different lowercase letters in the figure indicate significant (p < 0.05) differences between germplasm under the same period.
Figure 4. External and internal qualities of different-textured jujube fruits: (a) single-fruit weight; (b) longitudinal diameter; (c) transverse diameter; (d) soluble solid; (e) vitamin C; (f) titratable acid; (g) soluble sugar contents. Different lowercase letters in the figure indicate significant (p < 0.05) differences between germplasm under the same period.
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Figure 5. Anatomical structure of different-textured jujube fruits: (a) ‘2-11-10’ half-red period; (b) ‘1-10-20’ half-red period; (c) ‘2-12-17’ half-red period; (d) ‘2-6-5’ half-red period; (e) ‘2-7-5’ half-red period; (f) ‘2-10-22’ half-red period; (g) ‘2-11-10’ full-red period; (h) ‘1-10-20’ full-red period; (i) ‘2-12-17’ full-red period; (j) ‘2-6-5’ full-red period; (k) ‘2-7-5’ full-red period; (l) ‘2-10-22’ full-red period.
Figure 5. Anatomical structure of different-textured jujube fruits: (a) ‘2-11-10’ half-red period; (b) ‘1-10-20’ half-red period; (c) ‘2-12-17’ half-red period; (d) ‘2-6-5’ half-red period; (e) ‘2-7-5’ half-red period; (f) ‘2-10-22’ half-red period; (g) ‘2-11-10’ full-red period; (h) ‘1-10-20’ full-red period; (i) ‘2-12-17’ full-red period; (j) ‘2-6-5’ full-red period; (k) ‘2-7-5’ full-red period; (l) ‘2-10-22’ full-red period.
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Figure 6. Cellular morphology of jujube fruits of different textures during the half- and full-red periods: (a) cell width; (b) cell length; (c) cell area; (d) pericarp thickness. Different lowercase letters in the figure indicate significant (p < 0.05) differences between germplasm under the same period.
Figure 6. Cellular morphology of jujube fruits of different textures during the half- and full-red periods: (a) cell width; (b) cell length; (c) cell area; (d) pericarp thickness. Different lowercase letters in the figure indicate significant (p < 0.05) differences between germplasm under the same period.
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Figure 7. Principal component analysis of different-textured jujube fruits. A: hardness; B: adhesiveness; C: cohesiveness; D: springiness; E: gumminess; F: chewiness; G: cell width; H: cell length; I: cell area; J: pericarp thickness; K: single-fruit weight; L: longitudinal diameter; M: transverse diameter; N: soluble solid content; O: vitamin C content; P: titratable acid content; Q: soluble sugar content.
Figure 7. Principal component analysis of different-textured jujube fruits. A: hardness; B: adhesiveness; C: cohesiveness; D: springiness; E: gumminess; F: chewiness; G: cell width; H: cell length; I: cell area; J: pericarp thickness; K: single-fruit weight; L: longitudinal diameter; M: transverse diameter; N: soluble solid content; O: vitamin C content; P: titratable acid content; Q: soluble sugar content.
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MDPI and ACS Style

Zhang, X.; Yan, M.; Sun, Y.; Zhou, X.; Yuan, Z.; Li, X.; Lin, M.; Wu, C. Textural Characteristics and Anatomical Structure of Hard- and Soft-Fleshed Jujube Fruits. Agriculture 2024, 14, 2304. https://doi.org/10.3390/agriculture14122304

AMA Style

Zhang X, Yan M, Sun Y, Zhou X, Yuan Z, Li X, Lin M, Wu C. Textural Characteristics and Anatomical Structure of Hard- and Soft-Fleshed Jujube Fruits. Agriculture. 2024; 14(12):2304. https://doi.org/10.3390/agriculture14122304

Chicago/Turabian Style

Zhang, Xiaodong, Min Yan, Yongle Sun, Xiaofeng Zhou, Ze Yuan, Xiangyu Li, Minjuan Lin, and Cuiyun Wu. 2024. "Textural Characteristics and Anatomical Structure of Hard- and Soft-Fleshed Jujube Fruits" Agriculture 14, no. 12: 2304. https://doi.org/10.3390/agriculture14122304

APA Style

Zhang, X., Yan, M., Sun, Y., Zhou, X., Yuan, Z., Li, X., Lin, M., & Wu, C. (2024). Textural Characteristics and Anatomical Structure of Hard- and Soft-Fleshed Jujube Fruits. Agriculture, 14(12), 2304. https://doi.org/10.3390/agriculture14122304

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