Next Article in Journal
Effects of Drought Stress on the Growth and Physiological Characteristics of Idesia polycarpa Maxim
Previous Article in Journal
Bionanocomposite Coating Film Technologies for Disease Management in Fruits and Vegetables
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Horticulturae
Volume 11
Issue 7
10.3390/horticulturae11070833
horticulturae-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Evaluation of Nutrient Composition and Bioactive Substances in Water Caltrop from Different Origins

by
Haizhen Si
1,
Yang Yi
1,2,
Limei Wang
3,
Wenfu Hou
1,
Hongxun Wang
2,3,
Youwei Ai
1 and
Ting Min
1,2,*
1
College of Food Science & Engineering, Wuhan Polytechnic University, Wuhan 430023, China
2
Hubei Key Laboratory for Processing and Transformation of Agricultural Products, Wuhan Polytechnic University, Wuhan 430023, China
3
School Biology & Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan 430023, China
*
Author to whom correspondence should be addressed.
Horticulturae 2025, 11(7), 833; https://doi.org/10.3390/horticulturae11070833
Submission received: 10 June 2025 / Revised: 5 July 2025 / Accepted: 10 July 2025 / Published: 14 July 2025
(This article belongs to the Section Plant Nutrition)
Browse Figures
Versions Notes

Abstract

This study analyzed eight origins of water caltrop: HH; XG; XT; ST; JY; CZ; YN; JX. The evaluations focused on visual appearance, nutritional quality, and bioactive substances. Additionally, the shells and pulp of the JY were examined for the same parameters. The results demonstrated that the JY exhibited the highest total phenolic content (121.74 mg GAE/100 g) and total flavonoid content (196.67 mg GAE/100 g). The XG demonstrated the highest water content (87.35%) and soluble protein content (15.36 mg/g). JX exhibits the highest total phenolic and flavonoid content, as well as the strongest DPPH radical scavenging rate in the fruit pulp, indicating its superior biological activity and antioxidant capacity compared to water caltrop from other regions. In addition, JX has the highest soluble solids and sugar content in fruit pulp, indicating a sweeter taste. The YN exhibited the highest pulp starch and lowest water content. Principal component analysis revealed that the pulp of the ST and the shell of the JY scored the highest. These findings provide valuable insights for evaluating and processing the nutritional quality of water caltrop from different sources and provide a theoretical basis for consumers to choose water caltrop according to their needs.

1. Introduction

Water caltrop (Trapa spp.) belongs to the Trapaceae family and is commonly known as the rhombus or water chestnut. Its main species are classified based on the morphology into three categories: hornless water caltrop, two-horned water caltrop (T. bispinosa), and four-horned water caltrop (T. quadrispinosa Roxb.) [1]. Water caltrop is an annual aquatic herbaceous plant and also an important aquatic economic plant. Water caltrops are suitable for wet and muddy areas with temperate climates, such as ponds and swamps. Water caltrops prefer warm, humid, and sunny environments, but are not resistant to frost. Their optimal temperature is 25–36 °C and the water depth is around 60 cm. The old water caltrop is easy to grow when it falls into the mud. It sprouts and sprouts in March, blooms from April to August, opens at night, closes during the day, and moves with the moon’s fullness. The fruit ripens from July to September. Water caltrop has been cultivated in Asia for thousands of years. It commonly grows in freshwater wetlands, lakes, ponds, and stagnant river sections in tropical, subtropical, and temperate regions [2]. Water caltrop is popular among consumers for its crunchy texture and juicy pulp [3].
Water caltrop is highly valued for its nutritional content and is often called the “underwater peanut.” According to Chiang et al. [1], carbohydrates are the primary components of water caltrop pulp, with starch content being particularly abundant. Studies have demonstrated that the starch content in water caltrop pulp can reach 142–156 g/kg [1]. As the growing period extends, the starch content in the water caltrop further increases [4]. Research by Li et al. indicates that, in addition to starch, the fruit pulp of water caltrop is rich in various minerals, including potassium, phosphorus, and iron, with potassium content being notably high, which aids in maintaining the body’s water and electrolyte balance [5]. Additionally, the fat content in water caltrop pulp is low, ranging from 0.1% to 0.5% [1], the protein content in the pulp of water caltrops is about 11% to 19% [6], making it a healthy food. Studies have demonstrated that the dietary fiber in water caltrop promotes intestinal peristalsis and helps lower cholesterol and triglyceride levels, preventing coronary heart disease and diabetes [6]. Li [7] identified gallic acid, followed by catechins, as the primary bioactive compound in the fruit pulp of water caltrop. Water caltrop is a highly nutritious ingredient and offers many health benefits. Its pulp’s nutrients and bioactive compounds present significant potential for applications in food and healthcare products. Some studies have focused on food processing technologies utilizing water caltrop pulp as the primary raw material. Pei et al. [8] developed a functional cookie for patients with diabetes using water caltrop and seaweed sugar, which features a crispy texture and distinctive water caltrop aroma. Yan et al. [9] developed a yogurt product with sweet taste and high nutritional value by using water chestnut, water caltrop, and pure milk as the main raw materials.
Water caltrop sales and processing typically focused on pulp, producing many water caltrop shell by-products. Although the shell cannot be consumed fresh, the diamond-shaped shell extract is rich in flavonoids, phenolic compounds, and other bioactive ingredients, offering significant food and medicinal value with immense development potential [10]. Niranjan et al. [11] identified gallic acid, caffeic acid, quercetin, and kaempferol in the pericarp of three different water caltrop origins. In addition, research by Li [7] revealed that caffeic acid is the prominent compound in the shells of water caltrop. Moreover, some studies have indicated that water caltrop shell extract inhibits the growth of human gastric cancer cells in vitro [12]. Regarding bacteriostasis, water caltrop shell extract has proven effective in inhibiting a range of common pathogenic bacteria. The polyphenolic compounds in water caltrop shells exhibit great promise in antidiabetic and immunomodulatory applications. The bioactive substances in water caltrop shells have found widespread application in developing healthcare products, functional foods, and pharmaceuticals. Lu et al. [13] developed a water caltrop shell fiber chewable tablet using water caltrop shell as the primary ingredient, which promotes intestinal peristalsis and aids digestion. The active ingredients in water caltrop shells have also been employed to produce natural food additives and preservatives with antibacterial and antioxidant properties. These examples highlight the significant development potential of water caltrop shells in the food and medicinal fields, owing to their rich bioactive substances. They are expected to play a crucial role in the burgeoning health industry in the future.
There are notable differences in the nutrient composition and bioactive substances of water caltrop from different origins [5]. Although some studies have examined the nutrient composition of water caltrop, research focusing on the nutrient composition and functional active substances of origins from different origins remains limited, with insufficient species coverage. Existing studies predominantly focus on individual parts of the plants, with few addressing the combined evaluation of water caltrop pulp and shell. This gap in research restricts the ability to ensure the quality of water caltrop during processing and storage. It is essential to select suitable raw materials based on specific processing and storage requirements to maintain optimal standards in the market. This study investigated water caltrop from eight different regions, focusing on the shell and pulp of these water caltrops from different sources, and analyzed the overall quality of water caltrop. The study examined various parameters such as appearance, texture, nutrient composition, phenolic substances, and antioxidant capacity in the fruit shells and pulp of water caltrop from different origins. The findings aim to provide theoretical insights into the characteristics of water caltrop from different origins and to support the development of precise selection strategies.

2. Materials and Methods

2.1. Plant Material

Hubei Province has selected three production areas for water caltrops, namely Xiantao, Honghu, and Xiaogan. Xiantao (113°45′ E, 30°35′ N), Xiaogan (113°42′ E, 30°38′ N), and Honghu (113°19′ E, 29°50′ N) have a humid climate in June. The precipitation in Xiantao is 200–300 mm; the precipitation in Xiaogan is 250–350 mm, with occasional rainstorm; Honghu has a precipitation of 300–400 mm, with rain and heat occurring during the same season. The growth cycles of water caltrops are 120–130 days, 120–140 days, and 130–150 days, respectively. Honghu has large fruits and a high Xiaogan biomass.
Guangdong Province has selected three production areas for water caltrops, namely Shantou, Jieyang, and Chaozhou. Shantou (116°35′ E, 23°26′ N), Jieyang (116.37° E, 23.55° N), and Chaozhou (116.62° E, 23.67° N) have a warm and rainy June with a precipitation of 350–500 mm. The growth cycle of water caltrops is 110–135 days, and the plant height is 1.0–1.2 m. The biomass of Jieyang and Chaozhou is high.
Zhejiang Province has selected a production area for water caltrops, which is Jiaxing, Zhejiang. Jiaxing (120.75° E, 30.77° N) is mild and humid from May to June, with precipitation ranging from 300 to 400 mm. The growth cycle of water caltrops is 120–145 days, with many four cornered water caltrops. The plants are 1.2–1.5 m tall and have moderate biomass.
Yunnan Province has selected a production area of water caltrops, which is the Honghe Hani and Yi Autonomous Prefecture in Yunnan. The Honghe Hani and Yi Autonomous Prefecture in Yunnan Province (101°39′ E, 23°33′ N) is warm and humid from May to June, with precipitation of 300–400 mm. The growth cycle of water caltrops is 130–160 days, with a plant height of 1.0–1.2 m and a moderate biomass.
This study selected 8 different origins of water caltrops for analysis, namely Honghu and Hubei (HH); Xiaogan, Hubei (XG); Xiantao, Hubei (XG); Shantou, Guangdong (ST); Jieyang, Guangdong (JY); Chaozhou, Guangdong (CZ); Honghe Hani and Yi Autonomous Prefecture, Yunnan (YN); and Jiaxing, Zhejiang (JX). After picking on the same day, farmers transport freshwater caltrops to the laboratory through express cold chain and store them in a refrigerator at 4 °C until further analysis. The fruit shell and pulp are separated during sample pretreatment before retesting.

2.2. Methodologies

2.2.1. Sample Preparation

Rinse the surface of water caltrops with ultrapure water to remove impurities. Separate the shell and pulp with a sheller. Cut the horseshoe shell and fruit pulp into small pieces with a disinfectant knife to avoid microbial contamination, and then store them on a tray.

2.2.2. Appearance and Color Difference

The quality of the entire water caltrop was assessed through standardized photography in a small studio using a Canon EOS 550D digital camera (Canon (China) Ltd., Beijing, China) [14].
The L*, a*, and b* values of the shell and pulp surface were determined using a JZ-500 universal colorimeter (Shenzhen Jinhuai Instrument and Equipment Co., Ltd., Shenzhen, China), with a uniform area randomly selected for measurement on the surface of the water caltrop [15].

2.2.3. Texture

The pulp of the water caltrop was cut into thick pieces, approximately 1 × 1 × 1 cm (length × width × thickness). The texture analyzer (Shanghai Baosheng Industrial Development Co., Ltd., Shanghai, China) was set to the Texture Profile Analysis (TPA) mode, with a P/45 probe, trigger force of 100 g, and initial, downward compression, and end upward speed of 10.0, 0.5, and 10.0 mm/s, respectively. The residence time between the two compression phases was set to 5 s, with a deformation value of 35% [16].

2.2.4. Water Content and Browning Degree

The trays were placed in an oven at 105 °C until a constant weight (±2 mg) was achieved. A total of 3 g of water caltrop was weighed and placed in the trays, dried in an oven at 105 °C (Beijing Yong Guangming Medical Instrument Co., Ltd., Beijing, China) to a constant weight (±2 mg). Each sample was tested in triplicate, and the water content was calculated as a percentage [17].
The browning degree of water caltrop was measured following the method described by Min et al. [18]. A total of 3 g sample of water caltrop was homogenized in an ice bath, centrifuged, and the supernatant warmed in a water bath at 25 °C for 5 min. Absorbance was measured at 410 nm using a UV-visible spectrophotometer (model A360, Aoyi Instruments, Shanghai, Co., Ltd., Shanghai, China), and the browning degree is expressed as A410 nm × 10.

2.2.5. Soluble Sugar Content, Starch Content, Soluble Protein Content, and Soluble Solids Content

Soluble sugar content was determined using the method described by Yang et al. [19], with results expressed as percentages.
Starch content was measured using the total starch assay kit (Beijing Solebo Biotechnology Co., Ltd., Beijing, China) following the manufacturer’s instructions. Separate soluble sugars and starch in the sample using 80% ethanol further decomposed starch into glucose using the acid hydrolysis method and determined glucose content using anthrone colorimetric method to calculate starch content. A total of 3 biological replicates were established.
Soluble protein content was determined using the soluble protein assay kit (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) following the manufacturer’s instructions. The principle of this method is to use the anions on the Coomassie Brilliant Blue reagent to bind with Protein-NH3+ in the sample, causing the solution to turn blue. The absorbance is measured at 595 nm and three biological replicates are performed. A total of 4 g of pulp tissue and 36 mL of phosphate-buffered solution (0.1 mol/L, pH = 7.0) were used to prepare the extraction mixture, which was centrifuged for 10 min (4 °C, 10,000× g); then, the supernatant was saved for subsequent measurement. Absorbance was measured three times at 595 nm, and the results were expressed in mg/g.
The total soluble solids content was measured using a portable refractometer (Hangzhou Pu’en Technology Co., Ltd., Hangzhou, China) following the method outlined by Xu [20].

2.2.6. Vitamin C (VC) Content, Total Phenolic Content, Total Flaonoid Content, and DPPH Radical Scavenging Rate

VC content was determined using the VC assay kit (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) according to the manufacturer’s instructions. The principle of this method is to rapidly react Fe3+ with reduced ascorbic acid to generate Fe2+, which then reacts with phenanthroline for color development. The sample was homogenized with phosphate-buffered solution (0.1 mol/L, pH = 7.0) at a ratio of 1:9 under ice bath conditions. After centrifugation at 4 °C at 10,000× g for 10 min, the supernatant was saved for later use. Absorbance was measured three times for each sample at 536 nm, and the results were expressed in µg/g.
The total phenol content was measured using the Folin–Ciocalteu method with minor adjustments [21]. In brief, 3.0 g of pulp tissue was ground with 30 mL of 60% ethanol, followed by centrifugation. Then, the absorbance was determined at 760 nm in triplicate using the Folin–Ciocalteu reagent. A standard curve was prepared using standard gallic acid to calibrate the total phenol content in freshly cut water caltrop, with the results expressed as mg GAE/100 g.
The total flavonoid content was determined according to the method of Chen et al. [22] with minor modifications. Five grams of pulp tissue and 50 mL of 60% ethanol were used to prepare the extraction mixture, which was centrifuged for 10 min (4 °C, 10,000× g). Rutin was used as a standard for quantifying total flavonoid content, and the results are expressed as mg GAE/100 g.
The DPPH free radical scavenging rate was determined using a slightly modified method described by Yi et al. [23] The method for determination of the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging rate was modified from the reference. A total of 2 g of the sample was homogenized in 25 mL ethanol and sonicated (50 °C) for 30 min and centralized for 10 min (4 °C, 10,000× g). The supernatant absorbance was then triply measured for each sample at 517 nm, with anhydrous ethanol used to blank the instrument. The results are expressed as a percentage (%).

2.2.7. Statistical Analysis

Data analysis was conducted using Origin software (version 2021, OriginLab Corporation, Northampton, MA, USA). Statistical significance testing (one-way ANOVA), correlation analysis, and principal component analysis (PCA) were performed using Statistical Package for the Social Sciences software (version 20.0, IBM Corporation, Armonk, NY, USA).

3. Results

3.1. Appearance

As can be seen from Figure A1, JX exhibited a four-horned morphology of water caltrop, whereas others displayed a two-horned structure. These differences primarily stem from variations in the water caltrop outline and morphology, influenced by its growth habit and genetic inheritance. Regarding coloration, JX and XG exhibited a distinctly reddish hue, while HH and XT appeared considerably greenish (Appendix A). A significant difference was observed in the appearance of various water caltrop origins (p < 0.05), as illustrated in Figure 1. The L* value represents the brightness level (Figure 1a). XG and JY exhibited lower L* values in their shells, reduced brightness, and a darker appearance compared to the other origins. As illustrated in Figure 1b, the YN has the highest L* value for its pulp, indicating superior surface brightness and a higher gloss, which enhances consumer appeal. The a* value represents the degree of red and green. As depicted in Figure 1c, the JX has the highest a* value for its shells, resulting in a noticeably redder appearance compared to the other origins. This red coloration is associated with the four-horned shape of the JX. In Figure 1d, the JY exhibits the highest value for its pulp, indicating a more pronounced red coloration on the pulp surface. The b* value represents the yellow–blue degree. As illustrated in Figure 1e, XG and JX shells have the lowest b* value, while Figure 1f depicts that JY and YN have the lowest b* value for pulp.

3.2. Texture

Texture plays a crucial role in consumers’ perception of agricultural product quality [24]. Genetic characteristics, storage conditions, growing period, harvesting stage, and processing methods influence the texture of fruits and vegetables. The pulp texture of water caltrop directly impacts its edibility and processing adaptability. These characteristics are closely linked to cell wall components, including the content and proportion of pectin, cellulose, and others, which determine pulp hardness and elasticity. Any disruption to the pectin structure due to external environmental changes can weaken plant cell integrity, ultimately leading to fruit softening and a decline in overall texture quality [25]. Significant differences were observed in the hardness, chewiness, and cohesiveness of water caltrop pulp across different origins (Table 1). The XT exhibited the highest pulp hardness, measuring 14,144.124 ± 1043.115 gf, 3.6 times that of the CZ. ST and JX demonstrated moderate pulp hardness, making them more suitable for slicing, steaming, and other processing methods to accommodate diverse consumer preferences for water caltrop consumption [26]. Distinct textural variations among fruit and vegetable origins are closely linked to cellular structure and cell wall composition. The expression levels and enzymatic activity of endogenous enzymes in fruits and vegetables also play a critical role in texture formation.
Chewiness is a key parameter that determines the ease of mastication in water caltrop, which directly influences the eating experience. Cohesion plays a vital role in assessing the quality stability of water caltrop during storage and processing, making it a crucial factor in evaluating shelf life and processing adaptability [27]. The JX exhibited the highest chewiness of the pulp, measured at 6073.649 ± 861.064 gf, and the highest cohesion was recorded at 0.129 ± 0.040, ranking first among the eight origins. These values indicate a superior pulp texture, with a more compact and homogeneous internal structure, contributing to a richer eating experience compared to the other origins. Previous studies on pumpkin [25], grapes [28], and lotus root [29] suggest that variations in textural characteristics among different origins provide diverse options for processing and utilization in fruits and vegetables. A deeper analysis of these attributes enhances the selection of optimal origins and improves processing applications for water caltrop.

3.3. Water Content and Browning Analysis

Water content greatly influences the freshness and flavor of fruits and vegetables. A higher water content enhances the tenderness and juiciness of fruits and vegetables, making it a key quality indicator. Fresh fruits and vegetables with elevated water content exhibit a delicate texture and distinct flavor. Certain origins develop more robust root systems, enabling efficient water absorption from the soil and promoting higher water content. Factors such as leaf thickness, surface area, and stomatal density influence plant transpiration, directly affecting water retention capacity [29]. The water content in the shell and pulp of water caltrop exceeded 60% (Figure 2a,b). Among the origins, the YN exhibited significantly lower water content, measuring 73.04% in the shell and 63% in the pulp, suggesting a weaker ability to retain water due to structural or physiological characteristics. Figure 1b indicates that the pulp water content of JX and XG was significantly higher than that of other origins, exceeding 88%. Adequate water content enhances crispness and juiciness, while insufficient water content degrades texture. However, excessive water content increases susceptibility to water loss and wilting during storage, resulting in quality degradation. As a result, maintaining optimal water levels throughout storage and transportation is essential to preserving superior quality.
The appearance of fruits and vegetables directly influences consumer buying decisions, with browning degree affecting aesthetic appeal and serving as a key indicator of freshness perception [30,31]. Browning primarily results from enzymatic reactions in water caltrop, where polyphnol oxidase and peroxidase oxidize phenolic compounds into quinones under aerobic conditions. These quinones subsequently polymerize to form melanin, leading to browning [32]. As illustrated in Figure 2c, the JX exhibited the highest shell browning at 7.80 A410 × 10, while the CZ recorded the lowest at 2.21 A410 × 10. The shell browning of the JX was 3.5 times higher than that of the CZ. Figure 2d illustrates that the XG exhibited the highest pulp browning at 2.520 A410 × 10. In contrast, the YN recorded the lowest pulp browning at 0.51 A410 × 10, with the XG exhibiting a 4.94-fold increased pulp browning degree compared to the YN. Elevated pulp browning alters the texture and diminishes flavor, negatively impacting overall quality. The factors that affect browning include differences in variety or origin, environmental conditions, and post-harvest treatments. Elevated temperature and humidity can accelerate enzymatic browning, increasing the degree of discoloration. Additionally, post-harvest storage conditions and processing methods considerably impact browning. Storage at low temperatures can slow the enzymatic reaction, thereby reducing the extent of browning [33].

3.4. Soluble Sugar, Starch, Protein, and Soluble Solids Content

Soluble sugar is a key indicator of the physiological state and quality of water caltrop, providing insights into its nutritional value, maturity, and environmental stress response. Additionally, soluble sugar notably influences soluble solids content [34]. The concentration of soluble sugar in fruit is determined by genetic traits, growth temperature, water availability, soil composition, and light intensity. Greater temperature fluctuations between day and night, particularly in warmer regions, enhance the photosynthesis of plants during the day while minimizing respiration at night, facilitating the accumulation of soluble sugar. Statistical analysis revealed significant differences (p < 0.05) in soluble sugars among water caltrop origins, highlighting genotype and physiological metabolism variations. Figure 3a illustrates that the XT contained the highest shell-soluble sugar content, reaching 11.01 mg/g. As depicted in Figure 3b, the JX exhibited a significantly higher pulp-soluble sugar content of 14.54 mg/g, suppressing other origins. The soluble sugar content of most water caltrop origins analyzed in this study exceeded the values reported by Singh et al. [35,36]. A high soluble sugar concentration of water caltrop enhances sweetness and flavor while contributing to nutritional value, supporting overall health when consumed in moderation. In addition, soluble sugars are crucial in plant response to environmental stress. Under adverse conditions, plants increase soluble sugar levels to improve adaptability by enhancing water retention, maintaining expansion pressure, and scavenging reactive oxygen species. Consequently, XT and JX of water caltrops may exhibit greater resilience due to their higher soluble sugar content, enabling them to better sustain physiological functions and maintain quality stability under unfavorable environmental conditions [37].
Starch is a primary nutrient component of water caltrop, making it a valuable and versatile starch resource. Moderate starch intake contributes to increased energy. The unique physicochemical properties of water caltrop starch enhance its potential for application in the food industry. Figure 3c,d reveal significant differences (p < 0.05) in starch content between the shell and pulp of various water caltrop origins. Some origins may possess a more efficient starch synthase system, enabling them to more effectively convert photosynthetically produced sugars into starch. Additionally, temperature and light intensity in the growing environment are important in starch accumulation. Under optimal conditions, water caltrop can enhance photosynthesis and accumulate greater starch content [37]. The pulp starch content in the water caltrop was markedly higher than the starch content in the shell. The shell starch content of the CZ was measured at 70.64 mg/g. As depicted in Figure 3d, the YN exhibited the highest pulp starch content, reaching 272.91 mg/g, which aligns with the findings of Jin [38]. In contrast, the JX contained the lowest pulp starch content, with a difference of approximately 4.4-fold compared to the YN. These variations highlight distinct physiological mechanisms in starch synthesis and accumulation across water caltrop origins.
Soluble proteins are essential nutrients closely linked to plant metabolism and senescence. The reduction in soluble proteins is a key aspect of macromolecular degradation that occurs as fruits age [39]. Significant differences (p < 0.05) in soluble protein content were observed among different water caltrop origins (Figure 3e). The XG exhibited the highest soluble protein content (15.22 mg/g) in its shell, surpassing all other origins. As illustrated in Figure 3f, the soluble protein content in the pulp of the ST and JY exceeded 14 mg/g, with the difference between these origins and the HH being approximately 8-fold. The soluble protein content in the pulp of HH was notably low, at only 1.59 mg/g.
Soluble solids, including sugars, organic acids, vitamins, and other soluble components, are an important indicator of the taste and ripeness of fruits and vegetables and serve as a key parameter for evaluating their internal quality [40]. Optimal temperature and adequate light conditions promote the accumulation and transformation of sugar in fruits, greatly influencing their growth, development, and soluble solids content. As depicted in Figure 3g, the soluble solids content in the pulp of all eight water caltrop origins exceeded 12%, surpassing the levels reported by Singh, et al. [35]. The JX exhibited the highest soluble solids content, with 20% in the pulp, ranking it as the first soluble among the eight origins of water caltrop. Soluble sugars greatly influence the sweetness of fruits and vegetables, serving as the primary component of soluble solids. Consequently, soluble solids are a key characteristic for evaluating the sugar level in fruits and vegetables [41]. The JX exhibits the highest soluble sugar content in the pulp and the highest soluble solids, demonstrating a positive correlation between these two factors. This observation aligns with the findings of Fang et al. [42].

3.5. VC, Total Phenols, Total Flavonoids, and DPPH Radical Scavenging Rate

VC is a vital bioactive compound in fruits and vegetables, primarily consisting of ascorbic acid and deoxyascorbic acid. It possesses significant antioxidant and antimicrobial properties, effectively scavenging free radicals in the body, delaying cellular aging, enhancing immunity, and positively influencing the quality and shelf life of post-harvest fruits and vegetables. Increasing VC content enhances the color, flavor, and nutritional value of fruits and vegetables while extending their shelf life [43,44]. Significant differences in VC content exist among various water caltrop origins, affected by factors such as origin, growing environment, and post-harvest management. As illustrated in Figure 4a, the VC content in the shell of water caltrops exceeded that in the pulp, indicating that water caltrops have stronger antioxidant capacity. Guangdong, located in the subtropical region of China, features a warm and humid climate suitable for the growth of water caltrop. These climatic conditions enhance the photosynthesis process of water caltrop, fostering the synthesis and accumulation of VC. The JY exhibited the highest VC content in the shell at 28.28 mg/100 g, while the XG contained the lowest VC content at 17.23 mg/100 g. In Figure 4b, the ST demonstrated the highest VC content in the fruit pulp at 7.32 mg/100 g, while the YN exhibited the lowest VC content at 2.17 mg/100 g. The VC content of ST was 3.37 times higher than that of the YN.
Phenolic compounds are crucial in defending plants against insect feeding, pathogen attack, and microbial infection. Concurrently, their potent antioxidant properties help plants eliminate excessive free radicals, reducing oxidative damage and enhancing their competitiveness in the natural environment. As an aquatic plant [45], water caltrop is rich in phenolics, especially in its shell portion. The phenolic content in the shell of water caltrop was notably higher than that in its pulp, with the total phenol content in the shell and pulp differing by as much as 110 times in specimens from the same origin. Figure 4c illustrates that the JY exhibited the highest total phenolic content in its fruit shell, reaching 121.74 mg GAE/100 g, while the XT demonstrated the lowest total phenolic content in the fruit shell at 69.83 mg GAE/100 g. The total phenolic content in the fruit shell of the JY was 1.74 times higher than that of the XT. The total phenol content in the shells of water caltrop in this study was higher than the results reported by Zhang et al. [46]. Figure 4d depicts that the JX exhibited the highest total phenol content in the pulp, with 3.68 mg GAE/100 g, while the XG demonstrated the lowest at 0.72 mg GAE/100 g. The total phenol content in the pulp of JX was 5.13 times higher than that of the XG. This study’s results exceeded the total phenolic content of water caltrop reported in the study by Lu et al. [47]. Phenolics in water caltrop exhibit various medicinal properties, such as antioxidant and antitumor activities, and significant differences in phenolic content and activity were observed among water caltrop from different origins. Previous research indicated that the total phenolic content in the shell of JY and JX was superior, aligning with the findings of this study [48].
Flavonoids, as abundant and widely distributed phenolic compounds in the plant kingdom, play a crucial role in physiological functions and ecological interactions [47]. Flavonoids participate in cell signaling, gene expression regulation, and adaptation to environmental stress, contributing to various plant life processes [48,49]. The total flavonoid content in water caltrop shells was markedly higher than in the pulp. Similarly, the total phenolic content between the shells and the pulp of the same species exhibited differences of up to 25-fold. As illustrated in Figure 4e, ST, JY, and JX exhibited high total flavonoids, each surpassing 185 mg GAE/100 g, while the XT demonstrated the lowest flavonoid content in the shell at 103.33 mg GAE/100 g. The favorable climate in these areas, characterized by optimal temperatures, ample sunlight, and abundant precipitation, creates ideal conditions for water caltrop growth. In addition, excellent soil fertility and water quality further support its development. The fertility of the soil and the exceptional water quality enhanced nutrient absorption in water caltrop, contributing to increased flavonoid content. Genetic variations among water caltrop origins from different regions may also influence flavonoid synthesis and accumulation efficiency. These factors collectively result in higher flavonoid content in water caltrop shells from JY, ST, and JX. As presented in Figure 4f, the total flavonoid content in the pulp of JX reached 26.33 mg GAE/100 g, significantly surpassing other pulp origins, with a content 3.65 times higher than that of the XG. The elevated flavonoid content in the JX of water caltrop may be attributed to the geographic location of JX. JX is located in the Hangjiahu Plain of the Yangtze River Delta and falls within the subtropical monsoon climate zone. It experiences four distinct seasons, abundant sunlight, ample precipitation, and fertile soil, all of which favor the water caltrop growth and promote flavonoid synthesis and accumulation [49].
Figure 4g illustrates that the DPPH free radical scavenging content in the shells of all eight origins exceeded 90%. Among them, ST, JY, and JX exhibited superior DPPH free radical scavenging ability, with rates exceeding 95%, surpassing the findings of Rehman et al. [50]. This enhanced activity may be attributed to the high levels of antioxidant-active compounds, such as polyphenols, flavonoids, and other compounds, present in their shells. These compounds effectively scavenge free radicals in the body, exhibit antioxidant properties, and potentially delay aging. Figure 4h depicts that DPPH free radical scavenging capacity in the pulp of JX and ST was stronger. This result aligns with the earlier finding that ST and JX have higher phenolic content. Studies have demonstrated that phenolics possess significant antioxidant activity, effectively scavenging free radicals and protecting cells from oxidative damage [49]. Therefore, the higher phenolic content in the shell and pulp of ST and JX contribute to their enhanced DPPH radical scavenging capacity.

3.6. PCA

PCA is a widely used dimensionality reduction technique that transforms high-dimensional datasets into low-dimensional representations through linear transformation. Principal Component Analysis (PCA) involves a mathematical process that transforms many (possibly) related variables into a (relatively) small number of uncorrelated variables called principal components. The first principal component explains as much variability as possible in the data, and each subsequent principal component explains as much remaining variability as possible [51]. This process reduced the data complexity while preserving its main features and information [52]. This study applied PCA to establish a comprehensive evaluation model for the key indicators of eight water caltrop origins in shells and pulp. This approach provides a scientific foundation for origin selection and product development. It helps avoid one-sided assessments that rely on a single indicator or a few general indicators to evaluate fruit quality.
This study developed a comprehensive model to quantitatively assess the nutritional attributes of water caltrop pulp. Nine quality indicators, including water content, total phenols, total flavonoids, soluble protein, starch, VC, soluble sugar, DPPH radical scavenging rate, and browning degree, were consolidated into three significant components through PCA, enabling a comprehensive evaluation of the water caltrop pulp’s quality profile.
Table 2 presents the first three principal component eigenvalues of water caltrop pulp, all greater than 1. The first principal component eigenvalue was 4.251, the second was 2.525, and the third was 1.179, with a cumulative contribution of 88.382% from these components. The first principal component primarily reflects variations in active ingredients, including total phenols, total flavonoids, and DPPH free radical scavenging rate. The second principal component was mainly associated with water content, browning degree, and starch. The third principal component mainly represents the content of soluble protein. Using the composite factor scores obtained from PCA, the following formulas were obtained:
PC1 = 0.283X1 + 0.21X2 + 0.227X3 − 0.002X4 + 0.248X5 + 0.116X6 + 0.126X7 − 0.028X8 − 0.175X9
PC2 = −0.106X1 + 0.014X2 − 0.002X3 + 0.379X4 + 0.104X5 − 0.04X6 + 0.008X7 − 0.349X8 + 0.334X9
PC3 = 0.117X1 − 0.091X2 + 0.033X3 − 0.024X4 + 0.356X5 + 0.708X6 − 0.332X7 − 0.006X8 − 0.134X9
PC = 0.534PC1 + 0.317PC2 + 0.148PC3
where PC1, PC2, PC3, and PC represent the first, second, and third principal components, and the composite principal components, respectively. X1 to X9 correspond to the standardized values for total phenols, total flavonoids, DPPH radical scavenging rate, water content, VC content, soluble proteins, soluble sugars, starch content and browning degree of water caltrop pulp.
Table 3 results indicate that in the first principal component, JX and ST achieved higher pulp scores than other origins. This outcome corresponds to their elevated total phenols, flavonoids, and DDPH levels, indicating their greater concentration of active ingredients and stronger antioxidant capacity. In the second principal component, the XG ranked highest in pulp score, demonstrating more intense browning and greater water content than other origins. The composite scores indicated that ST and JX ranked high in pulp scores, reflecting their higher content of active substances and superior nutritional value. These origins also performed better in the quality indicators represented by the principal components. PCA enabled a comprehensive evaluation and comparison of water caltrop pulp across different origins, offering a scientific foundation for breeding, cultivation, storage, and processing. This analysis also reveals the intrinsic relationship among various quality indicators in the pulp, providing valuable insights into the nutritive value and mechanism underlying quality formation in water caltrop.
To comprehensively evaluate the quality profile of water caltrop shells further, nine quality indicators, including total phenols, total flavonoids, DPPH radical scavenging, VC, soluble protein, soluble sugar, starch, browning degree, and water content, were condensed into four major components for PCA.
Table 4 indicates that the first principal component eigenvalue reached 3.788, mainly reflecting differences in active ingredients, including total phenols, total flavonoids, DPPH radical scavenging rate. The second principal component eigenvalue measured 2.103, which is primarily associated with soluble protein and browning degree. The third principal component eigenvalue reached 1.195, representing starch and soluble sugar. The fourth principal component corresponded to the water content. All four principal component eigenvalues for water caltrop fruit shells exceeded 1, with a cumulative contribution of 90.474%. Using the composite factor scores derived from PCA, the following formulas were established:
PC1 = 0.380X1 + 0.337X2 + 0.321X3 + 0.135X4 + 0.118X5 + 0.041X6 + 0.019X7 + 0.119X8 − 0.059X9
PC2 = 0.085X1 + 0.134X2 + 0.127X3 − 0.299X4 + 0.523X5 + 0.013X6 + 0.162X7 − 0.483X8 − 0.037X9
PC3 = 0.104X1 − 0.072X2 − 0.065X3 + 0.141X4 − 0.057X5 + 0.511X6 − 0.537X7 − 0.041X8 − 0.032X9
PC4 = −0.3X1 + 0.104X2 + 0.054X3 + 0.012X4 − 0.17X5 − 0.19X6 − 0.129X7 + 0.156X8 + 0.8X9
PC = 0.465PC1 + 0.258PC2 + 0.147PC3 + 0.130PC4
Table 5 results indicate that in the first principal component, JY, ST, and JX scored higher than other origins, demonstrating greater active ingredient content in the shells, strong free radical scavenging, and antioxidant capacity. Experimental findings by Zuo YuanYuan also confirmed that total polyphenol extracts from samples produced in JX exhibited the highest DPPH radical scavenging rate [26]. In the second principal component, the CZ achieved the highest score for the shells, attributed to its soluble protein. Composite scores revealed that the JY and JX ranked highest for their shells, possessing superior nutritional content and bioactive substances among the eight origins. The pulp of ST and the shell of JY ranked the highest, demonstrating excellent qualities through their high level of active compounds and significant nutritional value. These factors serve as the core indexes for quality assessment. This study provides a systematic and scientific comparison of quality characteristics across different water caltrop origins, offering valuable insights for precise raw material selection before shell processing to enhance the overall quality and commercial value of water caltrop.

4. Discussion

This study revealed variations in nutritional and functional active substances across different water caltrop origins. These compositional differences may result from genetic inheritance, growing conditions, and agricultural climate change across different regions [53].
Starch aging occurs exclusively in pasted starches and tends to decrease water retention while increasing hardness. The high starch and low-fat content of water caltrop provide medicinal benefits, aiding in the relief of gluten-induced diseases such as celiac disease, which impair intestinal digestion [6]. In this study, starch content was greatly higher in water caltrop pulp than in the shell. Elevated starch levels contribute to increased hardness of the water caltrop, as observed in YN and XT, where higher starch content in the pulp corresponds to greater hardness. This effect results from tightly arranged starch granules in the water caltrop forming a denser structure. As starch content rises, stronger interactions between granules further enhance the overall hardness of the horn [54]. The pulp of YN and XT in Table 1 exhibit lower water content, maximum hardness, and higher starch content. Previous studies have reported a negative correlation between water content and hardness and a positive correlation between water content and starch levels, aligning with the findings of Liu J [32]. Based on this correlation, the low water content and high starch content of the YN create a firmer, harder texture with a more powdery consistency, while the JX, with the highest water content and lowest starch content, has more tender and juicier texture. The high starch content of water caltrop enhances gelatinization and pasting properties in food processing, making it suitable for producing starchy foods, such as water caltrop powder and water caltrop cake. Water caltrop origins with low starch content are ideal for making low-GI foods. Research by Syed Zameer Hussain et al. highlights that optimizing resistant starch in water caltrops makes its flour a promising gluten-free and low-GI ingredient [55,56].
Research has indicated that the phenolic content of plants is quantitatively and qualitatively influenced by their genetic makeup. Different species within the same genus and different cultivars within the same species exhibit varying levels of phenolic compounds [57]. The high content of total phenols, total flavonoids, and vitamin C in JY fruit shells, ST, and JX fruit pulp may be due to the abundant sunlight, heat, and precipitation in Guangdong and Zhejiang provinces, which are conducive to the growth of water chestnuts and the synthesis of secondary metabolites. Adequate light can promote photosynthesis, increase organic matter accumulation, and provide a material basis for the synthesis of bioactive substances; higher temperatures can accelerate the rate of biochemical reactions, promote the activity of related enzymes, and accelerate the synthesis of phenolic and flavonoid substances. However, Hubei has relatively less sunshine hours; Yunnan has diverse climate types, and in some areas, the duration of light is affected by factors such as terrain. The temperature is relatively low and the precipitation situation is relatively complex. These factors may inhibit some metabolic activities and affect the accumulation of phenolic and flavonoid substances. PCA results revealed a strong correlation between DPPH radical scavenging rate and phenolic content in water caltrop [54]. The study’s findings confirm that the shells of water caltrop possess superior DPPH radical scavenging capacity. The DPPH free radical scavenging rate of water caltrop shells exceeded 90%, while the pulp demonstrated a scavenging rate above 66%, surpassing the findings of Rehman et al. [50]. JX and ST of the fruit pulp scored higher, with these origins containing elevated total phenolics and total flavonoids, indicating superior antioxidant capacity. The higher DPPH radical scavenging rate of ST and JX was strongly correlated with their high phenolic content, suggesting that these origins possess enhanced free radical scavenging capacity. These results align with the existing literature, which emphasizes that genetic and agronomic factors influence the phenolic composition of fruits [58].
The taste and quality of the water caltrop pulp as the primary edible portion are crucial for consumer preference [1]. The results demonstrated that higher soluble sugars, soluble solids, and lower starch content contribute to a crisper texture and fresher quality in water caltrop [59]. The shells are an excellent source of phenolics, which influence the appearance, flavor, and other quality attributes of water caltrop fruit [60]. The pulp of JX contains the highest levels of soluble sugars, soluble solids, and water content and the lowest starch content, giving it a crispier, sweeter texture and juicier pulp, which enhances the overall eating experience. The shells of JY have the highest levels of total phenolics, flavonoids, and VC content, indicating the strongest antioxidant ability. This high antioxidant ability and free radical scavenging ability capacity make the shell of this origin ideal for phenolic extraction, with application in food, medicine, and other industries [49]. Although the shells of water caltrop are often discarded due to their non-consumer nature, their rich phenolic content endows them with significant biological activity. The phenolic content of water caltrop shells varies considerably across different origins, emphasizing the importance of selecting material-based demand. By optimizing the processing conditions and techniques, the nutritional value of processed products can be notably enhanced, ensuring maximum retention and extraction of phenolic substances from water caltrop shells [61,62].

5. Conclusions

This study focused on eight different origins of water caltrop, analyzing and evaluating the nutritional and functional active substances. The results indicate that the starch content in the pulp of water caltrops is much higher than that in the shell. High levels of moisture content, soluble sugar content, and starch content can result in better and fresher taste of water caltrop fruit pulp, making it more suitable for fresh consumption, such as JX fruit pulp. The total phenols, total flavonoids, DPPH free radical scavenging rate, and VC content in the shells of water caltrop fruit are higher than those in the pulp. Water caltrop shells containing higher levels of phenolic and flavonoid substances have stronger biological activity and antioxidant capacity, making them more suitable for extracting and processing bioactive substances, such as JY shells. The findings offer valuable insights for differentiating water caltrop fresh food, processing technologies, and origins in the market. In the future, the variations among different water caltrop origins may facilitate the implementation of more targeted development strategies.

Author Contributions

Conceptualization, H.S.; methodology, H.S. and T.M.; software, Y.Y.; validation, H.S. and W.H.; formal analysis, H.S. and Y.A.; investigation, Y.Y. and W.H.; resources, L.W. and T.M.; data curation, H.W. and T.M.; writing—original draft preparation, H.S.; writing—review and editing, T.M., Y.Y. and H.W.; visualization, Y.A. and H.W.; supervision, L.W. and Y.Y.; project administration, H.S.; funding acquisition, T.M., H.W. and W.H. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Science and Technology Department of Hubei Province [2024BBB027].

Institutional Review Board Statement

This article does not contain any studies with human or animal subjects.

Data Availability Statement

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

Conflicts of Interest

The authors confirm that they have no conflicts of interest with respect to the work described in this manuscript. The authors declare no competing interests.

Appendix A

Horticulturae 11 00833 g0a1
Figure A1. Differences in the appearance of different origins of Water caltrops.
Figure A1. Differences in the appearance of different origins of Water caltrops.
Horticulturae 11 00833 g0a1

References

  1. Chiang, P.; Li, P.; Huang, C.; Wang, C.R. Chemical composition and physical characteristics of water caltrop during growth. J. Sci. Food Agric. 2009, 89, 1298–1306. [Google Scholar] [CrossRef]
  2. Adkar, P.; Dongare, A.; Ambavade, S.; Bhaskar, V.H. Trapa bispinosa Roxb.: A review on nutritional and pharmacological aspects. Adv. Pharmacol. Sci. 2014, 2014, 959830. [Google Scholar] [CrossRef]
  3. Señorans, F.J.; Ibáñez, E.; Cifuentes, A. New trends in food processing. Crit. Rev. Food Sci. Nutr. 2003, 43, 507–526. [Google Scholar] [CrossRef] [PubMed]
  4. Tran, P.L.; Lee, J.S.; Park, K.H. Molecular structure and rheological character of high-amylose water caltrop (Trapa bispinosa Roxb.) starch. Food Sci. Biotechnol. 2013, 22, 979–985. [Google Scholar] [CrossRef]
  5. Li, X.; Yin, J.; Du, S.; Yang, Z.; Liu, P.; Wu, X. Research progress on nutrition and medicinal value of aquatic vegetables. Yangtze River Veg. 2015, 32, 25–30. [Google Scholar] [CrossRef]
  6. Niu, F.L.; Dong, W.Y.; Cheng, G.; Liang, R.; Gong, H.W. Analysis of nutrients in Northeast water caltrops. Food Sci. 2002, 23, 272–274. [Google Scholar] [CrossRef]
  7. Li, Y. Study on Postharvest Quality, Physiological and Biochemical Characteristics and Enzymatic Browning of Sparganium stoloniferum Buchenau; Nanjing Agricultural University: Nanjing, China, 2006. [Google Scholar] [CrossRef]
  8. Pei, M.M.; Wu, Y.Q.; Wang, Y.Y.; Dong, T.T.; Wang, L.Y. Development of Sparganium stoloniferum Buchenau trehalose biscuits. J. Luoyang Norm. Univ. 2022, 41, 26–30. [Google Scholar] [CrossRef]
  9. Yan, B.Y.; Huang, A.N.; Li, L.; Zhang, C.Y.; Wang, O. Development of Sparganium stoloniferum Buchenau and water chestnut yogurt. Chin. Dairy Cattle 2022, 40, 47–52. [Google Scholar] [CrossRef]
  10. Long, H.R. Extraction, Separation, and Antioxidant Activity Study of Flavonoids from Sparganium stoloniferum Buchenau Shell; Guangxi University: Nanning, China, 2009. [Google Scholar] [CrossRef]
  11. Niranjan, A.; Verma, S.; Lehri, A.; Amla, D. High-performance thin-layer chromatographic analysis for the simultaneous quantification of four phenolic compounds in green, red, and black fruits of Trapa natans var. bispinosa Roxb. (Singhara). Jpc—J. Planar Chromatogr.-Mod. Tlc 2013, 26, 316–321. [Google Scholar] [CrossRef]
  12. Dong, J.L.; Gao, G.C.; Huang, H.; Zhu, Q.F.; Jiang, X.H. Research progress on chemical composition and pharmacological activity of Sparganium stoloniferum Buchenau shell. J. Jiaxing Univ. 2014, 26, 68–71. [Google Scholar] [CrossRef]
  13. Lu, M.; Zhou, Y.J.; Li, L.; Xu, S.Q.; Kan, Y.F. Development of Sparganium stoloniferum Buchenau shell fiber chewing tablets. Food Process. 2018, 17, 19–20. [Google Scholar] [CrossRef]
  14. Xie, Y.; Lin, Q.; Guan, W.; Cheng, S.; Wang, Z.; Sun, C. Comparison of sodium acid sulfate and UV-C treatment on browning and storage quality of fresh-cut potatoes. Quality 2017, 2017, 58–67. [Google Scholar] [CrossRef]
  15. Chen, J.; Xu, Y.; Yi, Y.; Hou, W.; Wang, L.; Ai, Y.; Min, T. Regulations and mechanisms of 1-methylcyclopropene treatment on the browning and quality of fresh-cut lotus (Nelumbo nucifera Gaertn.) root slices. Postharvest Biol. Technology 2022, 185, 111782. [Google Scholar] [CrossRef]
  16. Wang, H.; Chen, J.; Yi, Y.; Wang, L.; Hou, W.; Ai, Y.; Wang, H.; Min, T. Regulation and mechanism of ethylene treatment on storage quality of fresh-cut lotus (Nelumbo nucifera Gaertn.) root slices. Sci. Hortic. 2023, 313, 111900. [Google Scholar] [CrossRef]
  17. Xue, T.-T.; Ruan, K.-H.; Xu, H.-B.; Liu, H.-B.; Tang, Z.-S.; Yang, Y.-G.; Duan, J.-A.; Sun, X.-X.; Wang, M.; Song, Z.-X. Effect of different drying methods on the drying characteristics, chemical properties and antioxidant capacity of Ziziphus jujuba var. spinosa fruit. LWT 2024, 196, 115873. [Google Scholar] [CrossRef]
  18. Min, T.; Xie, J.; Zheng, M.; Yi, Y.; Hou, W.; Wang, L.; Wang, H. the effect of different temperatures on browning incidence and phenol compound metabolism in fresh-cut lotus (Nelumbo nucifera G.) root. Postharvest Biol. Technol. 2017, 123, 69–76. [Google Scholar] [CrossRef]
  19. Yang, Y.; Liu, R.; Han, Y.; Wu, W.; Fang, X.; Mu, H.; Gao, H.; Chen, H. Critical taste substances and regulatory pathways of fresh lotus seed pulps at different ripeness stages. Postharvest Biol. Technol. 2023, 205, 112522. [Google Scholar] [CrossRef]
  20. Xu, Y.; Yu, J.; Chen, J.; Gong, J.; Peng, L.; Yi, Y.; Min, T. Melatonin maintains the Storage quality of fresh-cut Chinese water chestnuts by regulating phenolic and reactive oxygen species metabolism. Food Qual. Saf. 2022, 6, fyac002. [Google Scholar] [CrossRef]
  21. Xu, Y.; Bao, Y.; Chen, J.; Yi, Y.; Ai, Y.; Hou, W.; Wang, L.; Wang, H.; Min, T. Mechanisms of ethanol treatment on controlling browning in fresh-cut lotus roots. Sci. Hortic 2023, 310, 111708. [Google Scholar] [CrossRef]
  22. Chen, Z.; Xu, Y.; Lu, Y.; Miao, Z.; Yi, Y.; Wang, L.; Hou, W.; Ai, Y.; Wang, H.; Min, T. Effect and mechanism of eugenol on storage quality of fresh-peeled Chinese water chestnuts. Front. Plant Sci. 2022, 13, 965723. [Google Scholar] [CrossRef]
  23. Yi, Y.; Han, M.-M.; Huang, F.; Wang, L.-M.; Min, T.; Wang, H.-X. Effects of a Lysine-Involved Maillard Reaction on the Structure and In Vitro Activities of Polysaccharides from Longan Pulp. Molecules 2019, 24, 972. [Google Scholar] [CrossRef] [PubMed]
  24. García-Segovia, P.; Andrés-Bello, A.; Martínez-Monzó, J. Textural properties of potatoes (Solanum tuberosum L., cv. Monalisa) as affected by different cooking processes. J. Food Eng. 2008, 88, 28–35. [Google Scholar] [CrossRef]
  25. Hu, X.; Ma, T.; Ao, L.; Kang, H.; Hu, X.; Song, Y.; Liao, X. Effect of high hydrostatic pressure processing on textural properties and microstructural characterization of fresh-cut pumpkin (Cucurbita pepo). J. Food Process Eng. 2020, 43, e13379. [Google Scholar] [CrossRef]
  26. Biliaderis, C.G.; Maurice, T.J.; Vose, J.R. Starch gelatinization phenomena studied by differential scanning calorimetry. J. Food Sci. 1986, 45, 1669–1674. [Google Scholar] [CrossRef]
  27. Gao, F.; Li, D.; Li, H.; Chen, H.; Mao, X.; Wang, P. Influence of Post-Heating Treatment on the Sensory and Textural Properties of Stirred Fermented Milk. Foods 2023, 12, 3042. [Google Scholar] [CrossRef] [PubMed]
  28. Zhang, W.; Mayinur, J.; Wang, M.; Han, S.A.; Xie, H.; Pan, M.Q. Analysis on the pulp texture, cell architecture and its physiological characteristics of different grape varieties. Acta Bot. Boreali-Occident. Sin. 2022, 42, 1870–1879. [Google Scholar] [CrossRef]
  29. Dong, W.; Liu, X.; Yi, Y.; Wang, L.; Hou, W.; Ai, Y.; Wang, H.; Min, T. Evaluation of Pre-Harvest Nutrient Composition and Functional Active Substances in Various Lotus Roots. Foods 2024, 13, 2297. [Google Scholar] [CrossRef] [PubMed]
  30. Tu, Y.; Yan, S.; Li, J. Impact of harvesting time on the chemical composition and quality of fresh lotus seeds. Hortic. Environ. Biotechnol. 2020, 61, 735–744. [Google Scholar] [CrossRef]
  31. Vella, F.M.; Calandrelli, R.; Laratta, B. Influence of ripening on polyphenolic content, degradative, and browning enzymes in Cantaloupe varieties (C. melo, L.). Horticulturae 2021, 7, 421. [Google Scholar] [CrossRef]
  32. Liu, J.; Peng, J.; Yang, J.; Wang, J.; Peng, X.; Yan, W.; Zhao, L.; Peng, L.; Zhou, Y. Comparative Analysis of the Physicochemical Properties and Metabolites of Farinose and Crisp Lotus Roots (Nelumbo nucifera Gaertn.) with Different Geographical Origins. Foods 2023, 12, 2493. [Google Scholar] [CrossRef]
  33. Xu, C.; Song, L. Research progress on browning control of fresh-cut fruits and vegetables. Food Saf. Guide 2022, 32, 188–192. [Google Scholar] [CrossRef]
  34. Tang, Y.; Ren, J.; Liu, C.; Jiang, J.; Yang, H.; Li, J. Genetic characteristics and QTL analysis of the soluble sugar content in ripe tomato fruits. Sci. Hortic. 2021, 276, 109785. [Google Scholar] [CrossRef]
  35. Singh, G.D.; Siingh, S.; Jindal, N.; Bawa, A.S.; Saxena, D.C. Physico-chemical characteristics and sensory quality of Singhara (Trapa natans L.): An Indian water chestnut under commercial and industrial storage conditions. Afr. J. Food Sci. 2010, 4, 693–702. Available online: https://academicjournals.org/journal/AJFS/article-full-text-pdf/FCB17F326177 (accessed on 12 May 2025).
  36. Singh, G.D.; Bawa, A.S.; Riar, C.S.; Saxena, D.C. Influence of heat-moisture treatment and acid modifications on physicochemical, rheological, thermal and morphological characteristics of Indian water chestnut (Trapa natans) starch and its application in biodegradable films. Starch 2009, 61, 503e513. [Google Scholar] [CrossRef]
  37. Ma, Y.; Lu, M.; Yuan, G.; Wang, X.; Liu, J.; Zhang, J.; Wang, D. Analysis of seven soluble sugar fractions from chestnut nuts. Econ. For. Res. 2024, 42, 215–223. [Google Scholar] [CrossRef]
  38. Jin, M. Effects of Different Packing Methods and Temperatures on the Storage Quality of Water Caltrop Fruit Pulp. Master’s Thesis, Wuhan Polytechnic University, Wuhan, China, 2021. [Google Scholar] [CrossRef]
  39. Yuan, X.; Wu, Z.; Li, H.; Wang, Y.; Liu, F.; Cai, H.; Newlove, A.A.; Wang, Y. Biochemical and proteomic analysis of ‘Kyoho’grape (Vitis labruscana) berries during cold storage. Postharvest Biol. Technol. 2014, 88, 79–87. [Google Scholar] [CrossRef]
  40. Zhang, H.; Zhao, Q.; Lan, T.; Geng, T.; Gao, C.; Yuan, Q.; Zhang, Q.; Xu, P.; Sun, X.; Liu, X.; et al. Comparative Analysis of Physicochemical Characteristics, Nutritional and Functional Components and Antioxidant Comparative Analysis of Physicochemical Characteristics, Nutritional and Functional Components and Antioxidant Capacity of Fifteen Kiwifruit (Actinidia) Cultivars- Comparative Analysis of Physicochemical Characteristics, Nutritional and Functional Components and Antioxidant Capacity of Fifteen Kiwifruit (Actinidia) Cultivars. Foods 2020, 9, 1267. [Google Scholar] [CrossRef]
  41. Del Rio, D.; Rodriguez-Mateos, A.; Spencer, J.P.E.; Tognolini, M.; Borges, G.; Crozier, A. Dietary (poly)phenolics in human health: Structures, bioavailability, and evidence of protective effects against chronic diseases. Antioxid. Redox Signal. 2013, 18, e1818–e1892. [Google Scholar] [CrossRef]
  42. Fang, L.; Wei, K.; Feng, L.; Tu, K.; Peng, J.; Wang, J.; Pan, L. Optical absorption and scattering properties at 900–1650 nm and their relationships with soluble solid content and soluble sugars in apple pulp during storage. Foods 2020, 9, 1881. [Google Scholar] [CrossRef]
  43. Yang, B.; Han, Y.; Wu, W.; Fang, X.; Chen, H.; Gao, H. Impact of melatonin application on lignification in water bamboo shoot during storage. Food Chem. 2022, 13, 100254. [Google Scholar] [CrossRef]
  44. Alañón, M.E.; Ivanović, M.; Gómez-Caravaca, A.M.; Arráez-Román, D.; Segura-Carretero, A. Choline chloride derivative-based deep eutectic liquids as novel green alternative solvents for extraction of phenolic compounds from olive leaf. Arab. J. Chem. 2020, 13, 1685–1701. [Google Scholar] [CrossRef]
  45. Hu, G.; Li, X.; Lai, A.; Liu, Y.; Zhang, Y.; Wang, J.; Sun, S.; Zhu, J.; Yang, M. Comparative analysis of the nutritional quality of Zizania latifolia cultivars harvested in different growing seasons. Foods 2023, 13, 30. [Google Scholar] [CrossRef] [PubMed]
  46. Zhang, Y.; Cai, S.; Ma, S.; Zhao, S.; Yi, J.; Zhou, L. Water caltrop (Trapa quadrispinosa Roxb.) shell improves oxidative stress and postprandial blood glucose in diabetes. Phenolic profiles, antioxidant activities and α-glycosidase inhibition of different fractions with in vitro and in silico analyses. Antioxidants 2022, 11, 1873. [Google Scholar] [CrossRef]
  47. Lü, H.; Zuo, Y.; Meng, X.; Ding, X.; Jian, T.; Liu, Y.; Ren, B.; Chen, J.; Li, W. Phenolic profiles, antioxidant activity and inhibition of digestive enzymes of water caltrop pericarps. J. Sci. Food Agric. 2022, 102, 2342–2351. [Google Scholar] [CrossRef]
  48. Zuo, Y.Y.; Lv, H.; Wu, Y.X.; Chen, J.; Jian, D.; Ren, B.; Li, W. Comparison on Total Phenols Content and Antioxidant Activity and Inhibitory Effect on α-Glucosidase Activity in Water caltrop Shells (Trapa natans Linn. Shells) from Different Regions. J. Plant Resour. Environ. 2018, 27, 112–114. [Google Scholar] [CrossRef]
  49. Tilistyák, J.T.; Kücsön, G. Evaluation of Trapa natans L. (water caltrop) harvested from Lake Tisza, Hungary. Rev. Agric. Rural. Dev. 2023, 12, 28–33. [Google Scholar]
  50. Rehman, A.U.; Khan, A.U.; Sohaib, M.; Rehman, H. Comparative Analysis of Nutritional Properties, Phytochemical Profile, and Antioxidant Activities between Red and Green Water Chestnut (Trapa natans) Fruits. Foods 2024, 13, 1883. [Google Scholar] [CrossRef] [PubMed]
  51. Paul, L.C.; Suman, A.A.; Sultan, N. Methodological analysis of principal component analysis (PCA) method. Int. J. Comput. Eng. Manag. 2013, 16, 32–38. Available online: https://www.researchgate.net/publication/325011441_Methodological_analysis_of_principal_component_analysis_PCA_method (accessed on 12 May 2025).
  52. Wen, X.; Xiao, Y.D.; Nie, M.M.; Li, D.; Liu, C.; Niu, L.; Bao, Y.; Tang, D. Comprehensive evaluation of blueberry crisp quality of different varieties based on principal component analysis. Food Sci. Technol. 2024, 45, 208–217. [Google Scholar] [CrossRef]
  53. Zhang, Z.W.; Huang, L.; Deng, Z.C.; Wang, Z.; Hu, C.; Jiang, W.; Zhang, Y.; Peng, Y.; Wang, Z. Research Progress on the Water Purification Function and Cultivation Technology of Trapa. J. Agron. 2022, 12, 37–41. [Google Scholar] [CrossRef]
  54. Ferrer-Gallego, R.; Hernández-Hierro, J.M.; Rivas-Gonzalo, J.C.; Escribano-Bailón, M.T. Influence of climatic conditions on the phenolic composition of Vitis vinifera L. cv. Graciano. Anal. Chim. Acta 2012, 732, 73–77. [Google Scholar] [CrossRef] [PubMed]
  55. Gani, A.; Haq, S.S.; Masoodi, F.A.; Broadway, A.A.; Gani, A. Physico-chemical, morphological and pasting properties of starches extracted from water chestnuts (Trapa natans) from three lakes of Kashmir, India, Braz. Arch. Biol. Technol. 2010, 53, 731–740. [Google Scholar] [CrossRef]
  56. Gluten, M.N.M. major histocompatibility complex, and the small intestine: A molecular and immunobiologic approach to the spectrum of gluten sensitivity (‘celiac sprue’). Gastroenterology 1992, 102, 330–354. [Google Scholar] [CrossRef]
  57. Cai, J.; Cai, C.; Man, J.; Zhou, W.; Wei, C. Structural and functional properties of C-type starches. Carbohydr. Polym. 2014, 101, 289–300. [Google Scholar] [CrossRef]
  58. Singh, J.; Kaur, L.; McCarthy, O.J.; Moughan, P.J.; Singh, H. Rheological and textural characteristics of raw and par-cooked Taewa (Maori potatoes) of New. J. Texture Stud. 2008, 39, 210–230. [Google Scholar] [CrossRef]
  59. Hussain, S.Z.; Beigh, M.A.; Naseer, B.; Amin, T.; Naik, H.R. Characteristics of resistant starch in water chestnut flour as improved by preconditioning process. Int. J. Food Prop. 2019, 22, 449–461. [Google Scholar] [CrossRef]
  60. GarcõÂa-Viguera, C.; TomaÂs-BarberaÂn, F.A.; Ferreres, F.; ArteÂs, F.; TomaÂs-Lorente, F. Determination ofcitrus jams genuine-ness by avonoid analysis. Z. Für Lebensm.-Unters. Und Forsch. 1993, 197, 255–259. [Google Scholar] [CrossRef]
  61. Gao, Z.M.; Luo, Y.H.; Chen, Z.L.; Pan, Z. Development of water chestnut peel fruit vinegar beverage. China Brew. 2010, 29, 164–166. [Google Scholar] [CrossRef]
  62. Wang, S.; Zhu, F. Dietary antioxidant synergy in chemical and biological systems. Crit. Rev. Food Sci. Nutr. 2017, 57, 2343–2357. [Google Scholar] [CrossRef] [PubMed]
Horticulturae 11 00833 g001
Figure 1. Shell L* values (a), pulp L* values (b), shell a* values (c), pulp a* values (d), shell b* values (e), pulp b* values (f) of different origins of water caltrop. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Figure 1. Shell L* values (a), pulp L* values (b), shell a* values (c), pulp a* values (d), shell b* values (e), pulp b* values (f) of different origins of water caltrop. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Horticulturae 11 00833 g001
Horticulturae 11 00833 g002
Figure 2. Shell water content (a), pulp water content (b), shell browning (c), and pulp browning (d) of different origins of water caltrops. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Figure 2. Shell water content (a), pulp water content (b), shell browning (c), and pulp browning (d) of different origins of water caltrops. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Horticulturae 11 00833 g002
Horticulturae 11 00833 g003
Figure 3. Soluble sugar of shell (a), soluble sugar of pulp (b), starch of shell (c), starch of pulp (d), soluble protein of shell (e), soluble protein of pulp (f), and soluble solids of pulp (g) of different origins of water caltrop. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Figure 3. Soluble sugar of shell (a), soluble sugar of pulp (b), starch of shell (c), starch of pulp (d), soluble protein of shell (e), soluble protein of pulp (f), and soluble solids of pulp (g) of different origins of water caltrop. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Horticulturae 11 00833 g003
Horticulturae 11 00833 g004
Figure 4. VC of shells (a), VC of pulp (b), total phenols of shells (c), total phenols of pulp (d), total flavonoids of shells (e), total flavonoids of pulp (f), free radical scavenging rate of DPPH in shells (g), and free radical scavenging rate of DPPH in pulp (h) of different origins of water caltrop. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Figure 4. VC of shells (a), VC of pulp (b), total phenols of shells (c), total phenols of pulp (d), total flavonoids of shells (e), total flavonoids of pulp (f), free radical scavenging rate of DPPH in shells (g), and free radical scavenging rate of DPPH in pulp (h) of different origins of water caltrop. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Horticulturae 11 00833 g004
Table 1. Hardness, chewiness, and cohesiveness of water chestnuts from different origins. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Table 1. Hardness, chewiness, and cohesiveness of water chestnuts from different origins. Note: Different letters, e.g., a, b, c, etc., indicate significant differences (p < 0.05) between origins at the same harvesting stage.
Hardness gfChewiness gfCohesiveness
HH7703.331 ± 1414.274 bc3158.659 ± 446.003 c0.129 ± 0.033 e
CZ5310.493 ± 867.348 d2604.313 ± 255.078 cd0.332 ± 0.038 bcd
ST5702.515 ± 1441.559 cd3399.198 ± 449.448 c0.230 ± 0.018 de
JY9092.815 ± 1492.718 b2207.109 ± 329.968 d0.264 ± 0.016 cd
YN12,746.764 ± 1729.968 a4533.122 ± 534.988 b0.439 ± 0.086 b
XT14,144.124 ± 1043.115 a2151.391 ± 464.048 d0.363 ± 0.036 bc
JX9598.567 ± 541.574 b6073.649 ± 861.064 a0.680 ± 0.136 a
XG6678.571 ± 816.277 cd1816.271 ± 375.514 d0.272 ± 0.013 cd
Table 2. Variance eigenvalues, contribution ratio, and composite matrix values of pulp principal components.
Table 2. Variance eigenvalues, contribution ratio, and composite matrix values of pulp principal components.
VariablePC1PC2PC3
Total Phenol Content0.283−0.1060.117
Total Flavonoid Content0.210.014−0.091
DPPH0.227−0.0020.033
Water Content−0.0020.379−0.024
VC Content0.2480.1040.356
Soluble Protein0.116−0.040.708
Soluble Sugar0.1260.008−0.332
Starch Content−0.028−0.349−0.006
Browning Degree−0.1750.334−0.134
Characteristic Values4.2512.5251.179
Variance Percentage/%47.23128.05513.096
Accumulate/%47.23175.28688.382
Table 3. Principal component scores, composite scores and ranking of component indicators of different origins of water caltrop pulp. (The “R” in the table represents the pulp of water caltrop).
Table 3. Principal component scores, composite scores and ranking of component indicators of different origins of water caltrop pulp. (The “R” in the table represents the pulp of water caltrop).
OriginsPC1PC2PC3PCRANK
HHR−0.202−0.589−0.942−0.4347
CZR−0.5120.6410.428−0.0073
STR1.332−0.2741.9020.9061
JYR−0.8250.6690.572−0.1445
YNR0.082−1.464−0.971−0.5648
XTR−0.1520.401−0.387−0.0114
JXR1.184−0.352−0.2820.4792
XGR−0.9050.968−0.319−0.2246
Table 4. Shell principal component variance eigenvalues, contribution ratio, and composite matrix values.
Table 4. Shell principal component variance eigenvalues, contribution ratio, and composite matrix values.
VariablePC1PC2PC3PC4
Total Phenol Content0.380.0850.104−0.3
Total Flavonoid Content0.3370.134−0.0720.104
DPPH0.3210.127−0.0650.054
Vc Content0.135−0.2990.1410.012
Soluble Protein0.1180.523−0.057−0.17
Soluble Sugar0.0410.0130.511−0.19
Starch Content0.0190.162−0.537−0.129
Browning Degree0.1190.483−0.0410.156
Water Content−0.059−0.037−0.0320.8
Characteristic Values3.7882.1031.1951.057
Variance Percentage/%42.08923.36713.27811.74
Accumulate/%42.08965.45678.73490.474
Table 5. Principal component scores, composite scores and ranking of component indexes of different origins of water caltrop shells. (The “K” in the table represents the shell of water caltrop).
Table 5. Principal component scores, composite scores and ranking of component indexes of different origins of water caltrop shells. (The “K” in the table represents the shell of water caltrop).
OriginsPC1PC2PC3PC4PCRANK
HHK−0.3700.642−0.6200.518−0.0304
CZK−0.2451.727−1.483−1.454−0.0755
STK0.8350.3260.1960.1610.5223
JYK1.9451.199−0.597−1.1050.9821
YNK−0.904−0.7250.2700.026−0.5646
XTK−1.058−1.298−0.2400.321−0.8218
JXK0.616−0.0300.5041.7800.5842
XGK−0.819−1.8401.970−0.247−0.5987
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Si, H.; Yi, Y.; Wang, L.; Hou, W.; Wang, H.; Ai, Y.; Min, T. Evaluation of Nutrient Composition and Bioactive Substances in Water Caltrop from Different Origins. Horticulturae 2025, 11, 833. https://doi.org/10.3390/horticulturae11070833

AMA Style

Si H, Yi Y, Wang L, Hou W, Wang H, Ai Y, Min T. Evaluation of Nutrient Composition and Bioactive Substances in Water Caltrop from Different Origins. Horticulturae. 2025; 11(7):833. https://doi.org/10.3390/horticulturae11070833

Chicago/Turabian Style

Si, Haizhen, Yang Yi, Limei Wang, Wenfu Hou, Hongxun Wang, Youwei Ai, and Ting Min. 2025. "Evaluation of Nutrient Composition and Bioactive Substances in Water Caltrop from Different Origins" Horticulturae 11, no. 7: 833. https://doi.org/10.3390/horticulturae11070833

APA Style

Si, H., Yi, Y., Wang, L., Hou, W., Wang, H., Ai, Y., & Min, T. (2025). Evaluation of Nutrient Composition and Bioactive Substances in Water Caltrop from Different Origins. Horticulturae, 11(7), 833. https://doi.org/10.3390/horticulturae11070833

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop