Dataset of ultrasound-assisted extraction of anthocyanin from the petals of Clitoria ternatea using Taguchi method and effect of storage conditions on the anthocyanin stability

Anthocyanins are natural water-soluble colourants with a number of reported health benefits and are an excellent alternative to artificial dyes. Anthocyanins from Clitoria ternatea were obtained using ultrasound-assisted extraction with glycerol-water (60:40 w/v). The anthocyanins in the extract were measured at wavelength 550 and 700 nm using a UV-visible spectrophotometer and expressed in terms of total anthocyanins content (TAC). Taguchi method was employed to optimize the extraction parameters that include the extraction time (30 to 50 min), extraction temperature (40 to 60 °C), and solvent to solid ratio (10:1 to 30:1), with TAC as the response. The obtained data showed the optimum extraction parameters as 30 min extraction time, 50 °C extraction temperature, and 10:1 solvent to solid ratio. The anthocyanin's storage stability was analyzed for 7 days at varying storage temperatures and exposure to light. The present dataset in this article indicated the glycerol-water system as a green alternative for anthocyanin extraction and acted as a storage medium. Furthermore, our methodology can be applied to optimize the anthocyanins extraction process, manipulate storage conditions and improve the extract quality.


a b s t r a c t
Anthocyanins are natural water-soluble colourants with a number of reported health benefits and are an excellent alternative to artificial dyes. Anthocyanins from Clitoria ternatea were obtained using ultrasound-assisted extraction with glycerol-water (60:40 w/v). The anthocyanins in the extract were measured at wavelength 550 and 700 nm using a UV-visible spectrophotometer and expressed in terms of total anthocyanins content (TAC). Taguchi method was employed to optimize the extraction parameters that include the extraction time (30 to 50 min), extraction temperature (40 to 60 °C), and solvent to solid ratio (10:1 to 30:1), with TAC as the response. The obtained data showed the optimum extraction parameters as 30 min extraction time, 50 °C extraction temperature, and 10:1 solvent to solid ratio. The anthocyanin's storage stability was analyzed for 7 days at varying storage temperatures and exposure to light. The present dataset in this article indicated the glycerol-water system as a green alternative for anthocyanin extraction and acted as a storage medium. Furthermore, our methodology can be ap-plied to optimize the anthocyanins extraction process, manipulate storage conditions and improve the extract quality.
© , and solvent to solid ratio (10:1, 20:1, and 30:1), and the response was TAC. TAC was expressed in terms of the differences in the absorbance (wavelength 550 and 700 nm) between pH 1.0 and 4.5. Parameters for the storage stability were temperature (4 and 25 °C) and lighting conditions (fluorescent light and dark). The percentage of anthocyanins degradation was expressed in terms of absorbance differences at wavelength 550 nm during 0, 1, 3, 6, and 7 days of storage. Description of data collection UAE with glycerol-water (60:40 w/v) was used to prepare the anthocyanins extract from the dried powder of C. ternatea flowers. Taguchi method was used to optimize the extraction condition of UAE. The absorbance value of anthocyanins in the extract was measured at wavelength 550 nm. TAC was quantified using the spectrophotometric pH differential method. Storage stability of anthocyanins extract was performed at different temperature and lighting condition. All samples were stored in a tightly sealed glass bottle and fully covered with aluminum foil except for fluorescent light condition. Absorbance readings at wavelength 550 nm were taken at 0, 1, 3, 6, and 7 days of storage for the percentage of anthocyanins degradation analysis.

Value of the Data
• The dataset of anthocyanins obtained from UAE from the C. ternatea flowers with glycerolwater system can be used as a reference to enhance the extraction efficiency of bioactive compounds in terms of quantity and quality compared to other types of extraction method. • The data provided in this article can be used by natural food colourant producers and the food industry to optimize the anthocyanins extraction process and storage conditions. • The data showed the extractability and storage ability of bioactive compound using glycerolwater system and the potential application of this solvent in the food, cosmetic, nutraceutical and pharmaceutical industry for developing new natural products. • The dataset of TAC and the absorbance reading of anthocyanins extract from C. ternatea can serve as a benchmark for the analysis of anthocyanins-related compounds from different types of plant, fruit, berries, herb and spices. Fig. 1 and Supplemental data 1 show the TAC in solvent screening process using UAE at 40 °C for 15 min, using 10:1 of solvent to solid ratio. Solvents used were water and glycerol-water (60:40 w/v and 90:10 w/v). Table 1 and Supplemental data 2 tabulate the TAC and S/N ratio data delivered from the Taguchi method with 27 experimental runs. The data in Table 2 describes the effects of factors estimated based on the means of TAC. Fig. 2 visualize the magnitudes of the main effects of factors. Data in Table 3 correspond to Fig. 3 , which reports the interaction of 3 factors at 3 levels on the S/N ratio. The ANOVA and percentage of contribution for the 3 factors are displayed in Table 4 . Table 5 and Supplemental data 3 illustrate the validation of predicted and experimental values (TAC and S/N ratio). Table 6 and Supplemental data 4 report the percentage of anthocyanin degradation in lighting conditions (fluorescent light and dark) and temperature (4 and 25 °C). Supplemental data 5 shows the lack of fit, model summary, coefficients, regression equation of S/N ratio, fits and diagnostics for unusual observations. The raw and processed dataset of solvent screening, Taguchi L27 experimental result, optimization

Materials
Fresh C. ternatea flowers were collected from a private residence in, Kedah, Malaysia. The fresh flowers were cleaned with tap water and dried under the sun. Only the blue color petals were selected ( Fig. 4 ) and used for extraction purposes. The dried petals were ground and sieved to particle size below 710 μm. The sample was stored at 4 °C in a tightly sealed container until further use.
Glycerol with a purity of 99.5% (QReC, New Zealand) was used to prepare green solvent. Potassium chloride (Merck, Germany) was used to prepare pH 1.0 buffer solution. tri-Sodium citrate-2-hydrate (Riedel-de Haen, Germany) and citric acid (R&M Chemicals, United Kingdom) were used to prepare citrate buffer solution at pH 4.5.

UAE and solvent screening
Water and glycerol-water (60:40 w/v and 90:10 w/v) were used for the screening process. Extraction was conducted by adding 1 g of C. ternatea powder into three different solvents with a solvent to solid ratio of 10:1 and maintained at 40 °C for 15 min in an ultrasonic bath (Elmasonic, S80H) [1] . After the extraction time, the extract was vacuum filtered using filter paper, followed by centrifugation at 40 0 0 rpm for 15 min. The supernatant was collected for further analysis. The solvent that produced the highest total anthocyanin content was used in the op- timization and storage stability test. The extraction and solvent screening were performed in triplicate.

Determination of total anthocyanins content
The TAC in the C. ternatea extract was determined using the spectrophotometric pH differential method [2] . The C. ternatea extract was diluted separately with pH 1.0 and pH 4.5 buffer solutions. The absorbance value of equilibrated sample solution was measured at wavelength 550 and 700 nm using a UV-visible spectrophotometer (Agilent Technologies, Cary 60). The absorbance value of diluted sample (A) and TAC were calculated using Eqs. (1) and (2) , respectively: Where MW is the molecular weight of the anthocyanins reference pigment (cyanidin-3glucoside, MW = 449.2 g/mol), DF is the dilution factor, ε is the molar absorptivity of the reference pigment (cyanidin-3-glucoside, ε = 26 900 L mol −1 cm −1 ), and l is the cuvette width (1 cm). The measurement of TAC was done in triplicate.

Experimental design
Taguchi method was adopted in this work to optimize the extraction condition. The three factors (extraction time, extraction temperature, and solvent to solid ratio), with three levels setting, were considered as independent variables and summarised in Table 7 . An L27 (3 3 ) orthogonal matrix showed 27 experimental runs derived from 3 factors (columns) with 3 levels (rows). The TAC (mg/L) was evaluated at the end of each experiment. The function higher the better was selected as maximizing the TAC was the main objective in this experiment. The function was represented as Signal-to-Noise (S/N) ratio and determined according to Eq.  Where n is the number of repetitions for an experimental combination, and y i is a performance value of the i th experiment. The extracts were prepared in triplicate.
The importance of factors on TAC was based on the delta value, and the highest S/N ratio for each factor at the particular level was selected as the optimum extraction parameter [3] .

Validation of experimental and predicted data
The experimental and predicted value of TAC and S/N ratio under optimum conditions were validated based on the percentage of bias [4] as stated in Eq. (4) . The experiment value was done in triplicate.

Anthocyanin's storage stability test
The effect of light on the stability of anthocyanin was studied in two conditions at room temperature. For dark condition, the C. ternatea extracts were stored in a tightly sealed glass bottle and were fully covered with aluminum foil. For light condition, the glass bottle was directly exposed to fluorescent light (Philips Lifemax, TLD 36 W/765, cool daylight). The effect of temperature was investigated at 4 °C and room temperature (25 °C). The extracts were stored in tightly sealed glass bottles wrapped with aluminum foils. The extracts were prepared in triplicate. The absorbance of all extract was measured at wavelength 550 nm using a UV-visible spectrophotometer (Agilent Technologies, Cary 60) on day 0, 1, 3, 6, and 7 of storage. The absorbance was used to determine the percentage of anthocyanin degradation using Eq. (5) , according to Askar et al. (2015) [5] : Where A initial is the initial absorbance of the sample solution, and A final is the absorbance at a specific time interval at different storage conditions.

Statistical analysis
All experiments were carried out in triplicates. The results of TAC and the percentage of anthocyanin degradation were expressed as the mean ± standard deviation. Taguchi experimental design was performed by Minitab 18 statistical software (Minitab, State College, PA, USA). Analysis of data was conducted using ANOVA to evaluate the significance of the independent variables and their interactions. The difference was considered statistically significant when the p -value ≤ 0.05.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have, or could be perceived to have, influenced the work reported in this article.