1 Introduction

Hangbaiju, a cultivar of Chrysanthemum morifolium widely produced in Zhejiang, China, is an important traditional medicinal and edible plant that has long been used in tea, food, and health-related products. Chrysanthemum has been cultivated in China for tea and food use for more than two thousand years, and the dried capitulum is commonly consumed both as a traditional Chinese medicine and as a functional food material (Yuan et al., 2015; Ouyang et al., 2022). In Hangbaiju specifically, the capitulum is rich in flavones and caffeoylquinic acids, which are regarded as the principal active substances and are associated with anti-inflammatory, antibacterial, antioxidant, and antidiabetic activities (Lu et al., 2024). Hangbaiju is also favored by consumers because of its disease-preventing and health-improving functions, and both its flowers and leaves show notable antioxidant, antibacterial, antiviral, anti-inflammatory, antitumor, and immunomodulatory activities (Liu et al., 2025). Beyond medicinal use, chrysanthemum products are valued for flavor, aroma, and sensory quality, which supports their role in health teas and other edible applications (Xu et al., 2022a). Because Hangbaiju quality directly determines its medicinal efficacy, edible value, and market competitiveness, establishing scientific quality evaluation criteria is essential. Current studies show that relying only on geographical origin or traditional experience can lead to biased quality judgment, whereas comprehensive evaluation based on chromatographic fingerprints, bioactive compounds, and bioactivity provides a more reliable basis for quality control (Lu et al., 2022). Consistent with this, flavones and caffeoylquinic acids are not only major active ingredients but also important indicators for evaluating Hangbaiju quality, while compounds such as chlorogenic acid, 3,5-O-dicaffeoylquinic acid, luteolin, and related flavonoids repeatedly emerge as key discriminatory or quality-marker substances across chrysanthemum cultivars.

The quality of Hangbaiju is not static, but is formed dynamically during flower development and is strongly influenced by harvest period. Developmental-stage studies on Hangbaiju have shown that total flavonoid content is higher in the early stages S1 and S2, while total polyphenol content rises first and then declines, peaking at S2, indicating that major active constituents accumulate preferentially before full senescence (Lu et al., 2024). More broadly in medicinal chrysanthemum, flavonoid and chlorogenic acid contents differ significantly across floral development stages and reach their highest values at the bud stage, while comprehensive analysis suggests that the best harvest stage for simultaneously obtaining relatively high active and nutritional ingredients lies between the bud and young flower stages. Similar patterns have been reported in other chrysanthemum materials, where most differential flavonoids and phenolic acids were higher at the initial or full-bloom stages than at late stages, supporting the idea that optimal harvest windows are closely tied to metabolite accumulation patterns (Yang et al., 2024). Even when antioxidant activity does not always shift in parallel, harvest stage still significantly affects moisture, phenolics, flavonoids, anthocyanins, and carotenoids, and its interaction with genotype can further shape functional quality (Julianti et al., 2026). In addition, morphological traits may reflect chemical quality: in a Hangbaiju-related subtype, smaller inflorescence diameter was associated with higher chlorogenic acid and 3,5-O-dicaffeoylquinic acid contents, suggesting that external appearance can have value when linked with internal markers in quality grading (Yang et al., 2025). Together, these findings indicate that harvest timing is a key determinant of the accumulation of active substances and therefore a central factor in the quality formation of Hangbaiju.

After harvest, drying is the critical processing step that further determines whether the intrinsic quality of Hangbaiju can be preserved, enhanced, or degraded. Drying is widely used to prolong shelf life, improve storability, and support the processing of chrysanthemum into teas and medicinal products, but it also alters chemical composition, color, aroma, microstructure, and bioactivity (Xu et al., 2022a; Wang et al., 2024). Multiple studies show that drying method significantly affects bioactive constituents and antioxidant properties in chrysanthemum flower heads (Yuan et al., 2015; Shi et al., 2017). In medicinal chrysanthemum, appropriate oven drying has been recommended at about 55~65 ℃, while for specific cultivars oven-drying at 60 ℃ or 70 ℃ produced favorable outcomes, indicating that suitable temperature ranges can improve the retention of active ingredients (Shi et al., 2017). Drying technology also matters beyond simple temperature control: combined infrared and hot-air drying increased chlorogenic acid, luteolin, total phenolics, and total flavonoids, and infrared-assisted methods strongly affected aroma retention and color behavior. Pulsed vacuum drying preserved total phenolics and flavonoids, enhanced antioxidant activity, and favored volatile retention under lower temperature and pulsed ratio conditions, while vacuum drying more generally was reported to retain antioxidant components in a shorter time (Sun et al., 2021; Lu et al., 2020). Microwave-assisted and combined pretreatments can also improve quality by inhibiting enzymatic browning and preserving biologically active compounds, although excessive heat or prolonged treatment may accelerate oxidation and degradation of flavonoids and other heat-sensitive constituents (Wang et al., 2019; Xu et al., 2022a; Miao et al., 2026). Recent work further shows that kill-green pretreatment can shorten subsequent drying time and improve color, phenolics, amino acids, volatiles, and sensory acceptance, emphasizing that processing sequence as well as drying mode contributes to final quality (Xu et al., 2024).

This study will investigate the effects of harvest period and drying methods on the formation and preservation of Hangbaiju quality, with the aim of further clarifying the major characteristics of quality changes in Hangbaiju under different harvest stages and processing conditions. The quality of Hangbaiju is not determined by a single factor, but results from the coordinated effects of multiple chemical markers, antioxidant-related properties, sensory traits, and morphological characteristics; meanwhile, floral developmental stage and post-harvest processing can both significantly alter these quality indicators. However, current studies often examine harvest stage or drying technology separately, and some studies focus mainly on other chrysanthemum cultivars. Therefore, a comprehensive evaluation of the combined effects of harvest period and drying methods on Hangbaiju remains necessary. By comparing changes in key active constituents, nutritional and functional indicators, and related quality traits of Hangbaiju under different harvest periods and drying methods, this study analyzes the patterns of quality formation and preservation, screens harvest and processing conditions suitable for the production of high-quality raw materials, and provides a reference for optimizing field harvest decisions, improving post-harvest processing parameters, enhancing product quality consistency, and promoting the standardized development of the Hangbaiju industry.

2 Quality Evaluation Indicator System for Hangbaiju

2.1 Appearance and commercial quality indicators of Hangbaiju

Appearance and commercial quality are the most direct indicators in the primary grading of Hangbaiju, because consumers and traders usually judge flower products first by inflorescence integrity, size, color, and external uniformity. Chrysanthemum flower color and luster are recognized consumer-facing quality traits, while petal color and shape also affect preference and market acceptance (Xu et al., 2022a; Wei et al., 2024). At the same time, appearance alone is not a reliable proxy for intrinsic quality, because different quality grades may show no obvious difference in smell or visible traits, and market practices such as sulfur fumigation can artificially improve appearance while reducing antioxidant activity and bioactive constituents (Wei et al., 2024).

For Hangbaiju-related materials, inflorescence morphology has practical grading value when linked with chemical markers. In Fubaiju, a subvariety introduced from Hangbaiju, inflorescence diameter was negatively correlated with chlorogenic acid and 3,5-O-dicaffeoylquinic acid, and first-grade samples had significantly smaller diameters and higher polyphenol contents (Yang et al., 2025). Studies using hyperspectral imaging further show that exterior morphology can be fused with spectral information to predict total flavonoids and chlorogenic acids with high accuracy, supporting the use of image-based appearance indexes as rapid commercial evaluation tools rather than purely subjective observations (Wei et al., 2024).

2.2 Active components and physicochemical indicators of Hangbaiju

Active components and physicochemical indexes are the core of scientific Hangbaiju quality evaluation, because the nutritive and commercial values of chrysanthemum tea depend directly on phytochemical composition. Flavones and caffeoylquinic acids are the main active ingredients of Hangbaiju and are explicitly identified as important indicators for evaluating its quality (Lu et al., 2024). Across chrysanthemum cultivars, chlorogenic acid, luteolin, apigenin-7-glucoside, cryptochlorogenic acid, and isochlorogenic acid C contribute strongly to varietal discrimination, while spectrum-effect analysis has further identified chlorogenic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, and kaempferol-3-O-rutinoside as candidate Q-markers for quality evaluation (Ouyang et al., 2022; Lu et al., 2022).

The physicochemical indicator system should therefore include total flavonoids, total phenolics, chlorogenic acid and related CQA derivatives, moisture-related drying sufficiency, antioxidant activity, and selected nutritional indexes such as amino acids, soluble sugars, and vitamin C. Developmental studies in Hangbaiju showed that total flavonoids were higher at S1-S2 and total polyphenols peaked at S2, while other chrysanthemum studies found that flavonoid and chlorogenic acid contents were highest at the bud stage or between the bud and young flower stages (Lu et al., 2024). Drying also reshapes these indexes: oven drying at suitable temperatures, microwave-hot air drying, pulsed vacuum drying, and infrared-assisted drying each improved retention of different phenolics or antioxidant properties, showing that physicochemical evaluation must be tied to post-harvest processing conditions rather than measured as a fixed inherent trait (Wang et al., 2019; Sun et al., 2021; Xu et al., 2022a).

2.3 Sensory quality and safety indicators of Hangbaiju

Sensory quality and safety indicators form the third essential dimension of Hangbaiju evaluation because chrysanthemum is both a medicinal and edible material used in tea and food applications (Xu et al., 2022a). Sensory quality includes aroma, taste, color stability, and overall acceptance after processing. Different drying strategies dramatically change aroma profiles, and infrared-hot air drying produced the highest volatile concentration, while kill-green pretreatment with high-humidity air impingement improved color and retained more phenolics, amino acids, volatile compounds, and higher sensory acceptance than steam kill-green (Xu et al., 2024).

Safety evaluation should emphasize authenticity, processing cleanliness, and the stability of active compounds during storage and heating. Appearance-based adulteration is a real concern in chrysanthemum tea, because sulfur fumigation can counterfeit quality while damaging antioxidant properties and causing loss of bioactive compounds (Wei et al., 2024). In addition, chrysanthemum flavonoids are sensitive to light, oxygen, high temperature, and extreme pH, so storage and processing stability should be treated as part of product safety and quality assurance (Miao et al., 2026). Functional verification can also assist sensory-safety grading: first-grade Fubaiju showed stronger saltiness and astringency by electronic tongue and stronger antibacterial effects against Escherichia coli and Staphylococcus aureus, indicating that sensory discrimination and biological activity can serve as auxiliary indexes in Hangbaiju quality evaluation (Yang et al., 2025).

3 Effects of Harvest Period on the Quality of Hangbaiju

3.1 Effects of harvesting at the bud stage and early flowering stage on the quality of Hangbaiju

Harvesting Hangbaiju at the bud stage and early flowering stage generally favors the accumulation of key medicinal constituents, especially flavonoids and chlorogenic-acid-related compounds. In Hangbaiju capitula, total flavonoids were higher at S1 and S2 than at later stages, and total polyphenols rose first and then declined, peaking at S2 (Lu et al., 2024). HPLC-based analysis of four Hangbaiju products likewise showed that total flavonoids and chlorogenic acid reached their maximum at the Hualei stage, with Taiju ranking next. In medicinal chrysanthemum more broadly, flavonoid and chlorogenic acid contents were highest at the bud stage, and comprehensive evaluation placed the best harvest window between the bud and young-flower stages when both active and nutritional ingredients were considered (Ma et al., 2016). Untargeted and targeted metabolomics in Chrysanthemum indicum also showed that most varying flavonoids and phenolic acids were higher at the initial stage than at the eventual stage, supporting the value of early harvest for preserving active compounds (Yang et al., 2024).

Early harvest also appears advantageous for commercial differentiation and antioxidant potential, although the exact optimum depends on which compounds are prioritized. Taiju, defined as flower heads with opened ray florets but closed tubular florets and harvested earlier than Duoju, showed higher caffeoylquinic acids and stronger antioxidant activities than the later-harvested Duoju samples (Gong et al., 2019). In Hangbaiju harvested at different collection periods, metabolomics identified distinct volatile and flavonoid markers between Taiju and Duoju, and in Taiju most of the differential flavor volatiles and five of six flavonoid markers showed upward trends, indicating that earlier harvest contributes to a unique flavor and efficacy profile (Yang et al., 2022). A related grading study on Fubaiju, a Hangbaiju subvariety, found that smaller inflorescence diameter was associated with higher chlorogenic acid and 3,5-O-dicaffeoylquinic acid, and these trends were consistent with changes across the chrysanthemum picking period (Yang et al., 2025). Together, these findings indicate that bud-stage to early-flowering harvest is usually more favorable when the goal is to maximize polyphenol-rich medicinal quality rather than flower size or yield.

3.2 Effects of harvesting at the full flowering stage on the quality of Hangbaiju

Harvesting at the full flowering stage often provides a balanced quality profile, especially when producers must weigh active constituents against morphology, harvest efficiency, and marketable output. Developmental classification work in edible Hangju separates blooming into five stages and places harvest standards around stages 4 and 5, indicating that practical harvest commonly occurs near full opening rather than at the earliest bud stages (Liu et al., 2025). A cultivar study comparing half-bloom and full-bloom flowers found that harvest stage significantly affected moisture, total phenolics, total flavonoids, anthocyanins, and β-carotene, even though antioxidant activity did not differ significantly overall (Julianti et al., 2026). The same study also showed that harvest stage interacted with cultivar to alter phenolics, anthocyanins, β-carotene, and antioxidant activity, which suggests that full-bloom performance cannot be judged independently of genotype (Julianti et al., 2026).

For Hangbaiju specifically, full bloom appears to be a compromise stage rather than the peak for most medicinal markers. The 2011 Hangbaiju harvesting-stage study showed that delaying harvest increased yield markedly, but the highest total flavonoids and chlorogenic acid occurred earlier than full flowering, while luteolin-7-O-glucoside and 3,5-O-dicaffeoylquinic acid peaked at the Taiju stage rather than the latest stage. In Fubaiju, literature summarized within the grading study noted that chlorogenic acid and 3,5-O-DCQA were higher at initial bloom than at full bloom, while luteolin-7-O-glucoside varied little across the Hangbaiju flowering period (Yang et al., 2025). Even so, full bloom can remain commercially acceptable because flower heads are morphologically complete and easier to standardize, and moderate environmental conditions can concentrate harvest timing and improve flower yield near marketable stages (Liu et al., 2025). Therefore, full-flowering harvest is suitable when a balance is needed between visual maturity, operational convenience, and acceptable internal quality, but it usually does not maximize the full spectrum of active ingredients.

3.3 Effects of harvesting at the late flowering stage on the quality of Hangbaiju

Harvesting Hangbaiju at the late flowering stage generally reduces core bioactive quality, especially for flavonoids, chlorogenic acid derivatives, and some antioxidant-related markers. In Hangbaiju metabolomic analysis, flavones and caffeoylquinic acids accumulated at higher levels in S1 and S2 and then gradually declined from S3 to S5, with S5 corresponding to the stage when the outer whorl of ray florets began to decay (Figure 1) (Lu et al., 2024). The broader chrysanthemum developmental study under UV-B likewise showed that flavonoid and chlorogenic acid contents were highest at the bud stage rather than later stages, while soluble sugar, amino acid, and vitamin C increased as flowers developed, demonstrating that late harvest shifts quality away from medicinal phenolics toward some nutritional traits (Ma et al., 2016). In Chrysanthemum indicum, eventual-stage samples differed clearly from initial and full-bloom samples, and most varying constituents were lower at the eventual stage than at initial or full bloom (Yang et al., 2024).

Late harvest may still increase flower yield and opening degree, but these gains tend to come with weaker medicinal and sensory advantages. The Hangbaiju stage-comparison study found that yield increased obviously as collection time was deferred, yet overall evaluation still identified the Taiju stage as the best harvest time when functional constituents, yield, and timing were considered together. Comparison of commercial Hangbaiju types also showed that the later-harvested Duoju, collected when both ray and tubular florets were fully opened, had lower caffeoylquinic acids and weaker antioxidant activities than the earlier-harvested Taiju (Gong et al., 2019). Because harvest time also affects inflorescence diameter, and larger-diameter samples are associated with lower chlorogenic acid and 3,5-O-dicaffeoylquinic acid in Fubaiju, excessive delay in harvest likely improves external fullness at the expense of internal quality markers (Yang et al., 2025). Overall, late flowering harvest is less favorable for high-quality Hangbaiju if the evaluation emphasizes medicinal actives, antioxidant capacity, and premium-grade commercial quality rather than yield alone.

4 Effects of Drying Methods on the Quality of Hangbaiju

4.1 Effects of sun drying and shade drying on the quality of Hangbaiju

Sun drying and shade drying are traditional methods for processing chrysanthemum, but their effects on Hangbaiju quality are not identical. Studies comparing sun-dried, shade-dried, and oven-dried chrysanthemum flower heads showed that drying process significantly altered both bioactive constituent contents and antioxidant properties, indicating that natural drying cannot be regarded as a neutral preservation step. Metabolomic comparison of shade drying and heat drying further showed that the two methods produced clear differences in flavonoids, phenolic acids, and terpenoids, and that the levels of key indicator compounds and their precursors also changed significantly between treatments. In that comparison, most flavonoids, major phenolic acids, terpenoids, and carbohydrates were higher after shade drying than after heat drying, suggesting that slower, milder dehydration is more favorable for preserving many medicinally relevant components (Chen et al., 2024).

However, the advantages of natural drying are method-specific and must be weighed against efficiency and quality stability. One study found that nature and vacuum drying were both beneficial for increasing phenolic contents and antioxidant capacities in chrysanthemum flowers, indicating that low-stress dehydration can help preserve functional quality (Lu et al., 2020). Another study reported that total phenols and total flavonoids in infrared-dried chrysanthemums were significantly higher than in shade-dried ones, which implies that shade drying does not necessarily maximize active-component retention when compared with improved low-thermal technologies (Xu et al., 2022a). More broadly, direct sun exposure in plant materials is often associated with higher losses of light- and heat-sensitive pigments, because open-air drying exposes tissues to oxygen, radiation, and prolonged dehydration time (Belwal et al., 2022). Therefore, for Hangbaiju, shade drying is generally preferable to sun drying for preserving internal quality, but its long drying cycle and weaker process control limit its suitability for standardized, large-scale production.

4.2 Effects of hot-air drying on the quality of Hangbaiju

Hot-air drying is the most common industrial method for chrysanthemum because the equipment is simple and the drying rate is fast, but product quality depends strongly on temperature control. Chrysanthemum studies consistently show that increasing hot-air temperature shortens drying time and increases drying rate and moisture diffusivity (Xu et al., 2022a). At the same time, prolonged exposure to hot aerobic conditions can cause losses of bioactive and volatile substances and can also induce browning and petal curling, so faster drying does not automatically mean better quality. In chrysanthemum flowers, conventional hot-air drying produced the lowest total flavonoid values in one direct comparison, which was attributed to reactions between flavonoids and oxidase during drying (Wang et al., 2019).

The best hot-air conditions therefore appear to be moderate rather than extreme. For flower heads harvested at different developmental stages, appropriate oven drying was recommended at 60 ℃ for Xiaobaiju and 70 ℃ for Taiju. Another study concluded that an oven temperature of about 55~65 ℃ could simultaneously maintain relatively high active and nutritional ingredient contents (Shi et al., 2017). Evidence from pulsed-vacuum and related low-oxygen drying also supports the same general principle: lower temperature or staged heating better protects color, chlorogenic acid, luteolin, total phenolics, total flavonoids, and antioxidant capacity, whereas excessive temperature increases thermal degradation despite higher efficiency (Figure 2) (Xu et al., 2022a). Variable-temperature drying can even increase phenolic compounds, total flavonoids, and antioxidant capacity in chrysanthemum tea, showing that controlled thermal profiles can promote quality formation rather than simple degradation (Sun et al., 2026). Thus, hot-air drying is practical for Hangbaiju processing, but its final quality is governed by the coordinated control of temperature, time, and oxygen exposure.

4.3 Effects of microwave drying and vacuum freeze-drying on the quality of Hangbaiju

Microwave drying and vacuum freeze-drying represent two contrasting technical routes for improving Hangbaiju quality: one emphasizes rapid dehydration and enzyme inactivation, and the other emphasizes low-temperature preservation. In medicinal chrysanthemum, flavone and chlorogenic acid contents increased significantly with increasing microwave power, although amino acid content decreased significantly under microwave treatment (Shi et al., 2017). Considering efficiency and energy consumption, microwave drying was identified as the most suitable method among four tested methods for retaining higher flavone, vitamin C, and soluble sugar contents. In a direct comparison of drying methods, microwave treatment for 30 s combined with 75 ℃ hot-air drying was the most effective at preserving biologically active compounds and produced higher antioxidant capacity and stronger acetylcholinesterase inhibition (Wang et al., 2019). Another kinetics study similarly found that mild microwave-assisted hot-air treatment retained higher total phenolics, total flavonoids, and seven monomeric compounds with only limited conformational change (Wang et al., 2018).

Vacuum freeze-drying generally performs best for preserving physical structure, appearance, and many bioactive compounds, but its cost and drying time are major drawbacks. Freeze-drying improves the bioactive composition and physical structure of chrysanthemum products, although it is often considered economically unrealistic for seasonal herbs because of high energy consumption and equipment investment (Xu et al., 2022a). In Taihang chrysanthemum, freeze-drying maintained phenylpropanoid-rich bioactive compounds, gave superior antioxidant activity, and also supported stronger antibacterial and pancreatic lipase inhibitory activities (Fan et al., 2024). Evidence from other dried floral materials points in the same direction: vacuum freeze-dried petals showed the best appearance, highest bioactive compounds and antioxidant activity, and the best sensory similarity to fresh infusions (Suo et al., 2023). Freeze-dried samples also tend to preserve lighter color and heat-sensitive carotenoids better than convective drying, although the retention of phenolics can still depend on the specific plant matrix (Chua et al., 2019). Therefore, for Hangbaiju, microwave-assisted drying is more advantageous when processing efficiency and active-component retention must be balanced, whereas vacuum freeze-drying is more suitable when the goal is premium-grade product quality and maximum preservation of appearance and functional constituents.

5 Interactive Effects of Harvest Period and Drying Methods on the Quality of Hangbaiju

5.1 Adaptability of Hangbaiju raw materials at different maturity stages to drying methods

The adaptability of Hangbaiju raw materials at different maturity stages to drying methods is mainly reflected in their different starting compositions, tissue states, and responses to heat and dehydration. Harvest stage significantly affects the functional constituents of Hangbaiju, and the contents of total flavonoids and chlorogenic acid were highest at the Hualei stage, while luteolin-7-O-glucoside and 3,5-O-dicaffeoylquinic acid peaked at the Taiju stage. Taiju and Duoju, which are harvested at different times, also show clearly different phenolic profiles and antioxidant properties, with Taiju containing higher caffeoylquinic acids and stronger antioxidant activities than Duoju (Gong et al., 2019). Metabolomic analysis further showed that Taiju and Duoju differ in both volatile oils and flavonoids, and that most characteristic flavonoids and flavor-related volatiles increased in Taiju, indicating that early-and mid-maturity materials enter drying with different chemical bases and flavor potentials (Yang et al., 2022).

Because the raw material differs by maturity stage, the most suitable drying conditions also differ. A direct study of chrysanthemum flower heads harvested at two developmental stages found that drying process significantly affected bioactive constituents and antioxidant properties, and recommended oven drying at 60 ℃ for Xiaobaiju and 70 ℃ for Taiju. More generally, the nature of the starting material, including harvesting time, strongly influences drying dynamics and compound degradation, so drying parameters should be optimized together with raw-material condition rather than chosen independently (Belwal et al., 2022). This interaction is also consistent with process studies showing that structural state governs drying behavior: tempering reduced moisture heterogeneity between the central and marginal parts of chrysanthemum and improved subsequent drying performance, indicating that flowers at different maturity stages are likely to differ in their tolerance to the same drying route (Xu et al., 2023).

5.2 Effects of harvest period and drying conditions on the retention of active components in Hangbaiju

The retention of active components in Hangbaiju depends on the combined effect of harvest period and drying conditions, because flowers harvested at different stages begin with different dominant compounds and these compounds differ in thermal stability. In chrysanthemum flowers, phenolic acids were more stable than flavonoids during dehydration (Lu et al., 2020). This matters for Hangbaiju because early or Taiju-stage materials are richer in flavonoids, chlorogenic acid, and caffeoylquinic acids (Gong et al., 2019), so poorly controlled drying can erase the compositional advantages created by earlier harvest. Quality-marker studies also indicate that chlorogenic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, and kaempferol-3-O-rutinoside are key compounds for chrysanthemum quality evaluation, making their retention especially important when assessing harvest-processing interactions (Lu et al., 2022).

The evidence suggests that moderate or staged drying preserves these compounds better than uncontrolled high heat, while some intensified methods can further improve retention. Conventional hot-air drying gave the lowest total flavonoid values in one comparison, whereas microwave-hot air drying for 30 s plus 75 ℃ hot air best preserved biologically active compounds and increased antioxidant capacity (Wang et al., 2019). In medicinal chrysanthemum, microwave drying retained higher flavone, vitamin C, and soluble sugar overall, but amino acid content fell as microwave power increased, showing that the best method depends on which quality dimension is prioritized (Shi et al., 2017). Pulsed vacuum drying and multi-stage low-oxygen drying better preserved chlorogenic acid, luteolin, total phenolics, and total flavonoids, while tempering-incorporated infrared-assisted hot-air drying further increased chlorogenic acid, luteolin, total phenolic content, total flavonoid content, antioxidant capacity, and volatile compounds (Sun et al., 2021; Xu et al., 2022a; Xu et al., 2023).

5.3 Effects of harvest-processing combinations on the comprehensive quality of Hangbaiju

The best harvest-processing combination for Hangbaiju should be judged by comprehensive quality, not by a single component, because appearance, color, aroma, antioxidant activity, and sensory acceptance often respond differently to the same treatment. Earlier-harvested Taiju appears to provide the strongest starting point for comprehensive quality, since it balances functional constituents with yield better than Hualei, Youju, or Quanju. It also shows stronger antioxidant activity than later-harvested Duoju and carries a distinctive flavor-related metabolite profile (Gong et al., 2019; Yang et al., 2022). This makes Taiju-stage raw material especially suitable for high-quality processing, provided that the drying method protects both phenolic compounds and volatile aroma substances.

Among processing options, no single method dominates all endpoints, but several combinations stand out. Infrared-assisted hot-air drying increased chlorogenic acid, luteolin, total phenolics, total flavonoids, and volatile concentration, while sequential IR-HAD plus HAD better controlled color deterioration (Xu et al., 2022a). High-humidity air impingement kill-green for 60 s improved PPO and POD inactivation, retained more individual phenolics, sugars, amino acids, and volatiles than steam kill-green, and produced higher sensory acceptance (Xu et al., 2024). Freeze-drying maintained bioactive compounds and strong antioxidant and antibacterial activities in Taihang chrysanthemum, but other work showed that microwave-assisted or moderate-temperature oven drying can provide better efficiency or a more practical quality-cost balance (Shi et al., 2017; Fan et al., 2024). For Hangbaiju, the current evidence therefore supports a strategy in which Taiju or near-Taiju raw material is paired with a moderate, staged, or assisted drying process rather than late-harvest material combined with simple high-temperature drying.

6 Comprehensive Quality Evaluation Methods for Hangbaiju

6.1 Determination and comparison of single quality indicators of Hangbaiju

The determination and comparison of single quality indicators of Hangbaiju should begin with the targeted quantification of representative active constituents. HPLC has been used to simultaneously quantify eight bioactive compounds in chrysanthemum flower heads harvested at different stages and subjected to different drying processes, showing that single-index comparison remains the foundation of process evaluation. Near-infrared hyperspectral imaging has also shown good feasibility for the rapid prediction of luteolin and quercetin in fresh and dry Hangbaiju, indicating that instrumental screening can complement conventional wet chemistry for routine quality control (He et al., 2021). In practice, chlorogenic acid, luteolin-7-O-glucoside, 3,5-O-dicaffeoylquinic acid, flavonoids, phenolics, soluble sugar, amino acids, and vitamin C are the single indicators most often compared across harvest and drying treatments (Shi et al., 2017; Sun et al., 2021).

Single indicators should not be limited to chemical contents alone, because sensory, morphological, and functional traits also discriminate quality. Inflorescence diameter was negatively correlated with chlorogenic acid and 3,5-O-dicaffeoylquinic acid in Fubaiju, and samples with smaller diameters had higher polyphenol contents, supporting the use of appearance traits as measurable grading indexes. Electronic tongue analysis further distinguished high- and low-grade samples by stronger saltiness and astringency, while antibacterial assays confirmed better inhibitory activity in the higher-grade group (Yang et al., 2025). Antioxidant activity can also serve as a single functional endpoint, and antioxidant activity–fingerprints based on HPLC-DPPH-MS and NIR calibration have shown strong predictive ability for chrysanthemum quality assessment (Zhang et al., 2022).

6.2 Construction of a multi-indicator comprehensive evaluation model for Hangbaiju

A multi-indicator comprehensive evaluation model for Hangbaiju should integrate fingerprint similarity, multi-component quantification, biological activity, and multivariate statistics into one framework. In Chrysanthemum morifolium, chromatographic fingerprints of 30 flower-head samples were analyzed by similarity analysis, cluster analysis, and principal component analysis, and the common peaks accounted for major differences among samples (Lu et al., 2022). Spectrum–effect analysis further linked chemical peaks to antioxidant activity and identified chlorogenic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, and kaempferol-3-O-rutinoside as candidate Q-markers, which provides a model for linking measurable compounds to actual efficac. A related integrated approach in edible chrysanthemum combined HPLC, chemometrics, chromatogram-effect relationships, and bioinformatics to discover Q-markers and authenticate samples, showing that multi-indicator models can simultaneously serve quality evaluation and authenticity control (Yuan et al., 2022).

For Hangbaiju, the construction of such a model should also include weighted evaluation and classification steps. Analytic hierarchy process can be used to assign weights to different indicators, simplify complex evaluation problems, and identify the best scheme when multiple traits must be balanced (Zhao et al., 2022). In garden chrysanthemum, AHP combined with K-means clustering generated comprehensive scores and classified materials into four grades, illustrating a transferable framework for grading Hangbaiju lots or process treatments (Zhao et al., 2022). Spectroscopic chemometric models also support rapid multi-index evaluation: excitation-emission matrix fluorescence with random forest regression predicted 12 functional compounds while simultaneously authenticating geographical origin, and this “two-in-one” strategy is directly relevant to rapid Hangbaiju screening (Guo et al., 2025).

6.3 Screening of the optimal combination of harvest period and drying method for Hangbaiju

The screening of the optimal combination of harvest period and drying method for Hangbaiju should be based on comprehensive quality rather than on yield or one compound alone. Harvest stage significantly affected the functional constituents of Hangbaiju, and the contents of total flavonoids and chlorogenic acid were highest at the Hualei stage, whereas luteolin-7-O-glucoside and 3,5-O-dicaffeoylquinic acid were highest at the Taiju stage (Zhao et al., 2022). Because yield increased as collection time was delayed, the best harvest period could only be selected after balancing constituent retention against output, and that comparison favored the Taiju stage overall (Lu et al., 2020). This conclusion is consistent with metabolomic evidence showing that Taiju and Duoju have distinct volatile and flavonoid profiles, giving Taiju a different flavor and efficacy basis (Yang et al., 2022).

Drying-method screening should then be matched to the selected harvest stage. For flower heads harvested at two developmental stages, the appropriate drying process was suggested to be oven-drying at 60 ℃ for Xiaobaiju and 70 ℃ for Taiju, directly showing that maturity stage changes the optimal drying condition. Other studies indicate that microwave drying best preserved flavone, vitamin C, and soluble sugar when efficiency was considered (Shi et al., 2017), while microwave treatment for 30 s combined with 75 ℃ hot air was most effective at preserving biologically active compounds and antioxidant capacity (Wang et al., 2019). More advanced methods such as tempering-incorporated infrared-assisted hot-air drying and pulsed vacuum drying further improved chlorogenic acid, luteolin, total phenolics, total flavonoids, antioxidant capacity, volatile retention, or color preservation (Xu et al., 2023; Sun et al., 2021). Across specialty crops more broadly, intermediate harvest timing and drying temperatures around 30~60 ℃ tend to perform best, which supports the principle that Hangbaiju optimization should avoid both overly early harvest and excessive thermal stress (Pedrosa et al., 2024).

7 Existing Problems and Optimization Strategies

7.1 Non-uniform harvest standards for Hangbaiju and optimization strategies

A major problem is that Hangbaiju harvest standards remain insufficiently uniform, even though harvest stage clearly changes composition, antioxidant capacity, and product identity. In Hangbaiju, total flavonoids and chlorogenic acid peaked at the Hualei stage, while luteolin-7-O-glucoside and 3,5-O-dicaffeoylquinic acid peaked at Taiju, and overall evaluation favored Taiju when constituents, yield, and timing were considered together. Taiju and Duoju also separate clearly by phenolic profile, with Taiju showing higher caffeoylquinic acids and stronger antioxidant activities, and PCA distinguished the two groups using phenolic variables (Gong et al., 2019). Metabolomics likewise identified 11 markers that can authenticate Taiju and Duoju, indicating that harvest period creates stable chemical signatures rather than only visual differences (Yang et al., 2022).

Optimization should therefore replace rough visual or customary picking rules with maturity-indexed harvest criteria. A practical framework is to define harvest windows by inflorescence opening stage together with indicator compounds such as chlorogenic acid, luteolin-7-O-glucoside, and 3,5-O-dicaffeoylquinic acid. Diameter-based grading can help operationalize this, because smaller-diameter Fubaiju samples had higher chlorogenic acid and 3,5-O-dicaffeoylquinic acid contents and were validated by sensory and antibacterial differences (Yang et al., 2025). Since Hangbaiju quality also varies with geography, harvest time, and cultivation management, unified standards should combine maturity stage with origin and batch testing rather than rely on calendar date alone (Zhang et al., 2023).

7.2 Instability of drying process parameters for Hangbaiju and optimization strategies

A second problem is the instability of Hangbaiju drying parameters, because different methods change active compounds, antioxidant properties, color, volatiles, and energy use in different directions. Drying process significantly affected bioactive constituents and antioxidant properties in Xiaobaiju and Taiju, and the suggested optimal oven conditions already differed by harvest type: 60 ℃ for Xiaobaiju and 70 ℃ for Taiju. More broadly, medicinal chrysanthemum studies found that the best oven temperature was about 55~65 ℃, while optimal microwave power, microwave time, steam kill-enzyme time, and kill-enzyme time each had different windows (Shi et al., 2017). The absence of a single best method is reinforced by metabolomics showing that shade drying and heat drying produced significantly different flavonoids, phenolic acids, and terpenoids, with most key flavonoids and phenolic acids higher after shade drying (Chen et al., 2024).

Optimization should focus on process stabilization by product type, not one uniform drying recipe. For quality retention, moderate or staged heating performs better than excessive heat: multi-stage pulsed-vacuum drying better protected color, chlorogenic acid, luteolin, total phenolics, total flavonoids, and antioxidant capacity than higher-temperature schedules (Xu et al., 2022b). Targeted process intensification can further improve consistency, because tempering-incorporated infrared-assisted hot-air drying reduced drying time and energy use while increasing chlorogenic acid, luteolin, total phenolics, total flavonoids, antioxidant capacity, and volatile number (Xu et al., 2023). Pretreatment control is also critical: high-humidity air impingement kill-green shortened subsequent drying time by up to 46.15%, improved color through faster PPO and POD inactivation, and retained more phenolics, sugars, amino acids, and volatiles than steam kill-green (Xu et al., 2024). For premium products, microwave-hot air, pulsed vacuum, or freeze-drying can be selected when the priority is bioactive retention rather than lowest cost (Wang et al., 2019; Sun et al., 2021; Fan et al., 2024).

7.3 Incomplete quality evaluation system for Hangbaiju and optimization strategies

A third problem is that the Hangbaiju quality evaluation system is still incomplete, because traditional judgment by habitat or processing history alone neglects bioactive ingredients and functional quality. A spectrum-effect study on Chrysanthemum morifolium concluded that evaluation strategies based mainly on habitat and processing can deviate from true quality, and identified chlorogenic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, and kaempferol-3-O-rutinoside as candidate Q-markers. Fingerprint similarity among 30 chrysanthemum samples ranged widely, and cluster analysis could divide them into multiple classes, showing substantial heterogeneity even within commercial materials (Lu et al., 2022). Methods that integrate chemical data with sensory traits are more discriminating: electronic tongue captured overall solution characteristics, and in Fubaiju the higher-grade group showed stronger saltiness and astringency together with better antibacterial activity (Yang et al., 2025).

Optimization should build a multi-indicator comprehensive evaluation model for Hangbaiju. A strong template is the combined use of chromatographic fingerprinting, multi-component quantification, antioxidant assays, and spectrum-effect relationships to define Q-markers and rank samples (Lu et al., 2022). Weighting methods such as analytic hierarchy process, followed by clustering, can convert multiple quality dimensions into comprehensive scores and grade categories (Zhao et al., 2022). Rapid instrumental models can support implementation: near-infrared hyperspectral imaging predicted luteolin and quercetin well in fresh and dry Hangbaiju, and newer clustering frameworks for edible chrysanthemum were proposed specifically to avoid information loss from using too few indicators (Xu et al., 2022b; Jing et al., 2024). In practice, the best strategy is to screen harvest–drying combinations against a weighted panel that includes marker compounds, antioxidant activity, aroma or sensory data, morphology, and where needed antibacterial or other functional endpoints.

8 Conclusion and Prospects

An appropriate harvest period is the basis for high-quality production of Hangbaiju because the flowering stage directly determines the accumulation of phenolic acids, flavonoids, volatile substances, antioxidant capacity, and even the sensory identity of the final product. Studies on Hangbaiju showed that harvest stage significantly affected functional constituents, with total flavonoids and chlorogenic acid highest at the Hualei stage, luteolin-7-O-glucoside and 3,5-O-dicaffeoylquinic acid highest at the Taiju stage, and the overall balance of constituents, yield, and harvest timing favoring Taiju as the best picking stage. Comparative work on Taiju and Duoju further showed that products harvested at different times differ substantially in phenolic profiles, antioxidant activity, flavor-related volatiles, and flavonoid composition, and metabolomic analysis identified 11 marker metabolites that can distinguish the two harvest periods. Related evidence from Fubaiju also showed that inflorescence diameter was negatively correlated with chlorogenic acid and 3,5-O-dicaffeoylquinic acid, and that smaller-diameter samples had higher polyphenol content and better sensory and antibacterial performance, which supports using maturity-linked morphological traits as operational harvest indices. More broadly, metabolomics-based work in Chrysanthemum indicum found that most varied active constituents were highest or relatively high at initial or full-bloom stages, reinforcing the general principle that intermediate maturity often provides the best quality foundation for chrysanthemum materials.

Rational drying methods are the key to maintaining Hangbaiju quality because drying not only removes moisture but also reshapes the retention of active compounds, aroma, color, antioxidant capacity, and microstructure. Direct evidence showed that drying process significantly affected the bioactive chemical contents and antioxidant activities of Xiaobaiju and Taiju, with suitable oven drying suggested at 60 ℃ for Xiaobaiju and 70 ℃ for Taiju, indicating that even closely related harvest materials require different drying settings. Across chrysanthemum studies, moderate or optimized drying usually outperformed uncontrolled heating: oven drying around 55~65 ℃ better balanced active and nutritional ingredients, pulsed vacuum drying preserved total phenolics, flavonoids, and marker compounds while improving antioxidant activity, and lower temperature or pulsed conditions better protected color and volatile components. Microwave-assisted and infrared-assisted methods also showed clear advantages, as microwave drying retained higher flavone, vitamin C, and soluble sugar under efficient conditions, microwave-hot air drying best preserved biologically active compounds and acetylcholinesterase inhibitory activity, and infrared-assisted or tempering-incorporated drying increased chlorogenic acid, luteolin, total phenolics, total flavonoids, antioxidant capacity, and volatile compounds while reducing energy use. At the same time, shade drying tended to preserve more flavonoids, phenolic acids, and terpenoids than heat drying, and even general chrysanthemum flower studies found better color, shape, and petal integrity under shade drying, which shows that the best method depends on whether priority is given to processing efficiency, medicinal components, or external appearance.

Standardization of harvest and processing is an important direction for upgrading the Hangbaiju industry because current quality differences across batches cannot be fully controlled by origin labels or traditional experience alone. Quality evaluation studies showed substantial variation even among commercial Chrysanthemum morifolium samples, with fingerprint similarities ranging from 0.640 to 0.956, and demonstrated that relying mainly on habitat and processing history while neglecting bioactive ingredients can lead to deviation in quality assessment. More robust strategies already exist: chromatographic fingerprinting combined with multi-component quantification, antioxidant evaluation, and spectrum-effect analysis identified Q-markers such as chlorogenic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, and kaempferol-3-O-rutinoside, while integrated chromatogram-effect approaches and antioxidant activity-fingerprint models provided practical frameworks for quality assessment and authentication. Rapid detection technologies also support industrial upgrading, since near-infrared hyperspectral imaging predicted luteolin and quercetin in fresh and dry Hangbaiju, and fluorescence spectroscopy with chemometrics achieved high-accuracy origin authentication and functional compound prediction in chrysanthemum materials. Future optimization should therefore establish standardized harvest criteria centered on maturity stage, build process-specific drying protocols for different product goals, and adopt weighted multi-index models such as AHP, clustering, and chemometric authentication to achieve stable grading, premium branding, and higher-value utilization of Hangbaiju.

Conflict of Interest Disclosure

The author affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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