Butterfly pea (Clitoria ternatea L.) is one of the plants containing antioxidant compounds, specifically inside its flower petals. The flower is edible and has a blue color, which is attributed to the pigment anthocyanin. The types of anthocyanins that are highly abundant in the flower petals are ternatins, (poly) acylated derivatives of delphinidin 3,3’,5’-triglucoside. Anthocyanins in the butterfly pea flower/BPF are mainly in the (poly)acylated form (Kazuma et al., 2003; Gamage et al., 2021). BPF anthocyanins are water-soluble and show higher thermal and storage stability than non-acylated anthocyanins, but less photostability. These characteristics make the anthocyanins of BPF suitable for food applications (Gamage et al., 2021). Further, Kazuma et al., (2003) explained that the chemical compounds inside the petals are flavonoids, anthocyanins, flavanol glycosides, kaempferol glycosides, quercetin glycosides, and myricetin glycosides. Flavanol glycosides of kaempferol, quercetin and myricetin are the major flavonoids that can be found in BPF. Fu et al., (2021); Jeyaraj et al., (2021); Gamage et al., (2021) mentioned that the anthocyanin extract or water extract of BPF showed significant radical scavenging activity.
       
In Indonesia, BPF has not been widely used in food applications. In some regions, it is used as a food coloring in traditional foods, cakes, rice products and beverages, but its use is limited due to its weak contribution to flavor and aroma. To address this limitation so that the product can be accepted well by consumers, an effervescent beverage was developed. The effervescent beverage has an acidic flavor and an effervescent effect, providing freshness. Laurent et al., (2023) mentioned that citric acid, tartaric acid, and sodium bicarbonate in effervescent granules have an important role in providing an effervescent effect. Citric acid and tartaric acid are organic acids that can react with sodium bicarbonate when they come in contact with water, releasing carbon dioxide gas. In this study, an effervescent beverage was developed containing an anthocyanin extract powder of BPF, formulated with citric acid, tartaric acid and sodium bicarbonate. This provides a potential approach for developing BPF into a functional beverage with antioxidant properties. These preparations contain active ingredients (BPF anthocyanins and other flavonoids/polyphenols) and effervescent agents, which can provide a splitting effect and release gases when the granules are diluted in water.
       
Anthocyanin extract powder of BPF, used as the main active ingredient in the effervescent beverage formulation, can be prepared using various drying techniques, such as thin-layer oven drying, spray drying, or sucrose crystallization with maltodextrin or sucrose as carrier and coating agents. However, the heating treatments involved in these processes may influence the stability of anthocyanins and other polyphenols within BPF. Previous research stated that one factor affecting anthocyanin degradation is temperature (Gamage et al., 2021). Therefore, selecting an appropriate drying method is essential to preserve the bioactive compounds and ensure the quality of functional food products, such as effervescent beverages. Accordingly, this research was conducted to formulate an effervescent powder beverage enriched with BPF anthocyanin extract powder prepared using different drying methods (thin-layer oven drying, spray drying, and sucrose crystallization) and to evaluate its physical, antioxidant and sensory properties. This research is expected to provide valuable information for developing effervescent powder beverages enriched with BPF anthocyanin as a functional beverage with health-related antioxidants.

Materials and chemicals
 
The present study was conducted at the laboratories of the Department of Agricultural Products Technology, Faculty of Agricultural Technology, Universitas Jember, Indonesia, from February to July 2024. The ingredients used for this study were obtained from a local market and supplier, except for BPF, which was harvested from the garden and sun-dried. All other chemicals and reagents used for the analytical procedures were of analytical grade.
 
Extraction and production of BPF anthocyanin extract powder
 
Dried BPFs were soaked in hot water (100°C) for 15 minutes and then filtered. This process was repeated three times and the resulting filtrates were combined. The BPF anthocyanin extract was subjected to a drying process, resulting in the production of an anthocyanin extract powder that is used as a primary ingredient in effervescent powder beverage formulations. The preparation of the anthocyanin extract powder was conducted via spray drying (inlet and outlet temperatures of 165°C and 87°C) and thin-layer oven drying at 60°C for three hours. Maltodextrin (DE 15) was used as a carrier and coating agent at a concentration of 10% in the total mixture. The preparation of anthocyanin extract powder also employed a crystallization technique utilizing sucrose, accompanied by heating and stirring treatments. The ratio of BPF anthocyanin extract to sucrose was maintained at 1:1.
 
Formulation and production of effervescent powder beverage
 
The effervescent powder beverages enriched with BPF anthocyanins were prepared by dry mixing ingredients of the acid and base phases, according to the method modification of Laurent et al., (2023). The acid phase comprises a mixture of 0.9 g of citric acid and 1.1 g of tartaric acid, with a base phase of 0.5 g of sodium bicarbonate. The mixture of acid and base phases powder was homogenized and subsequently combined with BPF anthocyanin extract powder, which was prepared using a variety of drying techniques, including thin-layer oven drying (0.5, 1 and 1.5 g), spray drying (0.5, 1 and 1.5 g), and sucrose crystallization (5, 10 and 15 g). Subsequently, the mixture was augmented with sugar powder (7 or 15 g), and ascorbic acid (0.09 g). The formulation of an effervescent powder beverage enriched with BPF anthocyanin is illustrated in Table 1.



Physical characterization
 
The pH was measured at room temperature using a pH meter that had been calibrated previously with buffer solutions at pH 4 and 7 (Bakhti et al., 2025). Color parameters were determined using a Minolta CR-400 Chroma Meter according to the method of Malien-Aubert et al. (2001). The sample was measured with a chromameter at five different points, producing outputs for L, a*, b*, C and °Hue.
 
Antioxidative properties
 
The total polyphenol content was measured spectrophoto-metrically using the Folin-Ciocalteu method, as originally described by (Singleton and Rossi, 1965). The total polyphenol content was expressed as milligrams of GAE per gram of sample (mg GAE/g), with GAE representing gallic acid equivalent. The anthocyanin content was analyzed using the single pH method, using pH 1, as described by Sari et al., (2025a). The anthocyanin content was expressed as milligrams of delphinidin equivalent per gram of sample (mg DE/g). The antioxidant capacity was analyzed using the DPPH radical scavenging method, as described by Mudoi and Das (2024); Sari et al., (2025b). Antioxidant capacity was expressed as milligrams of TE per gram of sample (mg TE/g), with TE representing the Trolox equivalent.
 
Sensory evaluation
 
The sensory evaluation was conducted using the hedonic rating method. The hedonic rating was performed to determine the preference level of panelists for effervescent powder beverages enriched with BPF anthocyanins, with attributes of color, taste, aroma, and overall acceptance assessed on a 7-point scale from 1 (dislike very much) to 7 (like very much) (Sari et al., 2019c).

In this study, BPF was transformed into an effervescent powder beverage to improve consumer appeal by combining BPF anthocyanins with a refreshing acidic taste. This product is an instant beverage with functional antioxidant properties. The primary ingredient of effervescent powder beverage is anthocyanin extract powder, produced by three drying methods: thin-layer oven drying, spray drying, and sucrose crystallization. The anthocyanin extract powder was added in varying quantities (Table 1), including citric acid (0.9 g), tartaric acid (1.1 g), sodium bicarbonate (0.5 g), ascorbic acid (0.09 g), and sucrose (7 or 15 g). Fig 1a shows the powder form of the effervescent powder beverages enriched with BPF anthocyanins. Upon rehydration (Fig 1b), the beverage exhibits a purple color, an acidic flavor, and effervescent characteristics. The effervescent effect arises from the reaction between acidic compounds (acidulants) and carbonates or bicarbonates, which produces carbon dioxide and imparts a refreshing sensation (Kumar et al., 2009). Anthocyanins serve as the primary pigments, giving the beverages their distinctive purple appearance.


 
Physical characteristic
 
The pH values of the effervescent beverages enriched with BPF anthocyanins, in their rehydrated liquid form, ranged from 4.96 to 5.19 (Table 2), reflecting their acidic nature and flavor. This is attributed to CO₂ dissolution during effervescent reactions, forming carbonic acid and lowering pH (Laurent et al., 2023). The acidic condition also contributes to the purple color of effervescent beverages enriched with BPF anthocyanins, as shown in Fig 1b.


       
Table 2 presents the color parameters of effervescent powder beverages enriched with BPF anthocyanins. Products F1-F3 produced by thin-layer oven drying treatment exhibited the highest lightness, L (78.6 to 94.4), and lowest chromaticity, C (1.73 to 2.02). Spray drying treatment (F4-F6) produced L values ranging from 63.1 to 77.3 and C values from 2.54 to 2.91. While sucrose crystallization treatment (F7-F9) had the lowest L values (48.5 to 60.5) and the highest C values (4.20 to 4.91). Overall, increasing the addition of BPF anthocyanin extract powder decreased L value and increased C value, consistent with a more intense coloration. The observed differences in color properties, specifically the lightness and chromaticity, were influenced by drying methods. Spray drying treatment led to lower L and higher C values due to short-term high-temperature exposure, whereas thin-layer oven drying, performed over three hours, preserved the higher lightness and lower chromaticity. Sucrose crystallization treatment produced the darkest and most chromatic powders, likely due to caramelized sugar residues and browning reactions during prolonged heating. Hue angles further distinguished the products, with Hue values of F1-F6 ranging from 299.69 to 335.71 (purple) and F7-F9 from 347.37 to 351.83 (reddish-purple). Anthocyanin extract powder contributes to the color properties of effervescent beverages.
 
Antioxidative properties
 
The antioxidative properties of effervescent powder beverages enriched with BPF anthocyanins, such as the total polyphenol content, anthocyanin content, and antioxidant capacity, are illustrated in Table 3. The variation in the quantity of anthocyanin extract powder addition exerted an influence on the total polyphenol content. Among the products treated with thin-layer oven drying, F3 exhibits the highest total polyphenol content compared to F1 and F2. Similarly, among the products treated with spray drying, F6 exhibits the highest total polyphenol content compared to F4 and F5. Moreover, among the products treated with sucrose crystallization, F9 exhibits the highest total polyphenol content compared to F7 and F8. However, products produced by sucrose crystallization (F7-F9) have the lowest range of total polyphenol content due to degradation from extended high-temperature treatment. Besides anthocyanins (ternatin), the effervescent beverages also contain other polyphenols, predominantly flavanol glycosides of kaempferol, quercetin and myricetin, which represent about 73% of total phenolics in BPF (Jeyaraj et al., 2021; Kazuma et al., 2003).


       
The anthocyanin content of this product is highly influenced by the amount of BPF anthocyanin extract powder added, with F3, F6 and F9 showing the highest levels within their respective drying methods (Table 3). The addition of more anthocyanin extract powder will result in a higher anthocyanin content. Products produced by sucrose crystallization also have a lower range of antocyanin content compared to thin-layer oven drying and spray drying treatment, which both have slightly different values. BPF petals predominantly contain ternatin A1-A3, B1-B4, C1-C5 and D1-D3, which are (poly)acylated anthocyanins recognized for their thermal stability (Kazuma et al., 2003; Gamage et al., 2021). However, anthocyanins represent only about 27% of total flavonoids in the BPF petals, with flavonol glycosides being more abundant (Kazuma et al., 2003).
       
The antioxidant property is the ability of compounds to donate hydrogen atoms or electrons to neutralize free radicals, thus preventing the damage caused by the free radicals (Tan and Lim, 2015). BPF anthocyanins and other flavonoids/polyphenols are reported to protect against cardiovascular, neurological disorders, cancer and diabetes due to their antioxidant capabilities (Gamage et al., 2021). The result analysis of the antioxidant capacity of these products (Table 3) showed that products obtained by sucrose crystallization treatment have the lowest range of values (5.08 to 5.74 mg TE/g) than the other drying methods, such as thin-layer drying (5.77 to 6.60 mg TE/g) and spray drying (5.90 to 6.96 mg TE/g). This result of antioxidant capacity correlated with total phenolic and anthocyanin content. Previous studies reported a positive correlation between total phenolic content and antioxidant capacity/DPPH assay (Wong and Tan, 2020). The contribution of other constituents, such as ascorbic acid, may also have enhanced the antioxidant capacity observed in the formulations.
 
Sensory characteristic
 
The hedonic rating sensory test was conducted to evaluate panelists’ preferences for effervescent powder beverages enriched with BPF anthocyanins. Attributes assessed included color, taste, aroma, and overall acceptance, rated on a 7-point scale. A scale range of 5-7 was considered an acceptable response, indicating good product acceptance (Table 4). Among all formulations, product F6 achieved the highest scores across attributes. Regarding the color attribute, product F6 scored 6.07 (‘like’), reflecting its clearer purple appearance and less brown color compared to products F4 and F5. In contrast, products treated with thin-layer oven drying and sucrose crystallization exhibited more brownish hues after rehydration (Fig 1b), which was met with low acceptance by the panelists. Product F6 also obtained the highest scores for taste (5.64, on a scale from ‘rather like’ to ‘like’), which were attributed to its acidic profile and effervescent sensation generated by the reaction of citric or tartaric acid and sodium bicarbonate. This acid-base reaction not only produces carbon dioxide, which creates the bubbly effect typical of effervescent beverages, but also lowers the pH of the solution, making it more acidic. The aroma attribute received lower scores overall, with F6 scoring 4.14 (neutral), consistent with the limited aroma typically associated with BPF-based products. This suggests that aroma-enhancing additives may be required to improve sensory appeal. In terms of overall acceptance, product F6 scored the highest, with a rating of 5.68 (ranging from ‘rather like’ to ‘like’). Across all drying methods, formulations with the highest addition of anthocyanin extract powder (F3, F6 and F9) achieved the highest scores in every attribute among their respective treatment groups. This suggests that a greater anthocyanin content contributes positively to panelists’ acceptance. Overall, spray drying treatment was the most preferred, followed by sucrose crystallization and thin-layer oven drying, respectively. Generally, mean scores of attributes remained below 6 (‘like’), indicating rather low acceptance. This may reflect panelists’ unfamiliarity with effervescent beverages derived from BPF, indicating a need for broader consumer education and product introduction.

Effervescent powder beverages enriched with BPF anthocyanins were developed using thin-layer oven drying, spray drying, and sucrose crystallization techniques. The products exhibited an acidic flavor, effervescent characteristics, and a purple to reddish-purple coloration, with measurable levels of polyphenols, anthocyanins and antioxidant capacity, which support their potential health benefits. Products obtained by thin-layer oven drying and sucrose crystallization appear more brownish after rehydration due to the high-temperature processing. Among the methods, spray drying treatment resulted in products with better antioxidative properties, as well as the highest sensory acceptance, particularly in terms of color, taste and overall preference. These findings revealed that products produced by spray drying have better properties. This research is expected to provide valuable insights for developing effervescent powder beverages enriched with BPF anthocyanins as functional products with health-related antioxidants that are applicable across food industries, from small-scale to large-scale food industries.

The present study was funded by Universitas Jember through the Hibah Kelompok Riset-KeRis research grant.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from using this content.
 
Informed consent
 
Sensory assessments were conducted in accordance with established ethical principles, guidelines, and regulations. Informed written consent was obtained from all participants involved in the study. The products that were subjected to testing were determined to be safe for consumption.

The authors declare that there are no conflicts of interest regarding the publication of this article.