Title Science and Technology Indonesia e-ISSN:2580-4391 p-ISSN:2580-4405 Vol. 8, No. 3, July 2023 Research Paper Spectrophotometric Change of Butterfly Pea (Clitoria ternatea L.) Flower Extract in Various Metal Ion Solutions During Storage Abdullah Muzi Marpaung1*, Dania Pustikarini1 1Food Technology Department, Swiss German University, The Prominence Tower Jl. Jalur Sutera Barat. No. 15, RT.003/RW.006, Panunggangan Tim., Kec. Pinang, Tangerang, 15143, Indonesia *Corresponding author: abdullah.muzi@sgu.ac.id AbstractThis study aimed to investigate the effect of six chloride salts on butterfly pea flower extract’s anthocyanins stability. The salts wereNaCl, KCl, CaCl2, MgCl2, FeCl3, and AlCl3. The samples were analyzed using a UV-Vis spectrophotometer to observe color degradationand change in hue during storage. The extraction of anthocyanins was done using a modified method, and the solutions were storedin dark vials at room temperature. The degradation kinetics of benzene derivatives, acyl groups, non-anthocyanin flavonoid, flavyliumcation, quinonoidal base and anionic quinonoidal base were evaluated using the first-order reaction, and the half-life was calculated.The effect of metal ions was studied by analyzing the change in absorbance of each band using regression analysis and a slopetest. The results showed that monovalent (Na+ and K+) and divalent (Ca2+ and Mg2+) ions did not result in a significant shift in thespectrogram. Trivalent metal ions (Al3+ and Fe3+) had limited interaction with the anthocyanins, heightened the brown color, anddecreased the overall color quality. K+, Ca2+, Mg2+, Al3+, and Fe3+ ions showed the ability to improve the stability of the extract’scolor, while Na+ tended to accelerate color degradation. The pattern of changes in the spectrogram during storage suggests thatcolor degradation occurs in two ways: the unfolding of hydrophobic interactions and the deacylation of anthocyanin. Trivalent metalions showed the best stability performance, with Fe3+ preventing the unfolding of hydrophobic interactions and Al3+ hindering thedeacylation. The combination of the two is highly likely to improve the color stability of the butterfly pea flower extract. However,both increase the browning index, thus decreasing color quality. This research highlights the potential of adding cations to improvethe color stability of the butterfly pea flower extract, making it a more attractive food coloring agent. KeywordsAnthocyanin, Butterfly Pea Flower, Color Degradation, Metal Ions, Stability, UV-Vis Spectrophotometer Received: 12 February 2023, Accepted: 10 May 2023 https://doi.org/10.26554/sti.2023.8.3.367-372 1. INTRODUCTION The butterfly pea (Clitoria ternatea L.) flower extract is a rich source of anthocyanins that are well-known for their deep purple-blue color and their stability in low acidic solutions (Marpaung et al., 2017) . This relatively high stability is due to the presence of polyacylated anthocyanins in the butterfly pea flower extract, which has intramolecular copigmentation that helps to prevent the loss of color. The color of butterfly pea flowers can be used as food color- ing, but further research is required to ensure the color remains stable. Factors such as pH, chemical structure, light, heat, and metal ions can impact the stability of the color in butterfly pea flowers. Previous studies have investigated the effect of metal ions on the stability of anthocyanins from different sources, with varying results. Some studies have found that cations can improve anthocyanin stability, while others have found that they can provoke instability. For example, Na+ has been found to decrease (de Rosso and Mercadante, 2007; Hubber- mann et al., 2006), improve (Dangles and Brouillard, 1992; Figueiredo and Pina, 1994; Peng et al., 2016), or have no effect on anthocyanin stability (Wang et al., 2010) . K+ increases the color intensity and improves stability (Czibulya et al., 2015) , while others have found that Ca2+ enhances color Li (2014) without affecting stability (Ren et al., 2014) , but in some cases, it decreases stability (Ratanapoompinyo et al., 2017) . Studies have observed no impact on anthocyanin color from Mg2+ (Sigurdson et al., 2016) . Fe2+ and Fe3+ enhance the color and stabilize the configuration of anthocyanins but also destroy an- thocyanins (Li, 2014; Peng et al., 2016; Ratanapoompinyo et al., 2017). Al3+ has a positive effect on the stability of antho- cyanins (Maylinda et al., 2019; Peng et al., 2016), while others have found no effect (Li, 2014) . To date, there has been no study on the effect of metal ions https://crossmark.crossref.org/dialog/?doi=10.26554/sti.2023.8.3.367-372&domain=pdf https://doi.org/10.26554/sti.2023.8.3.367-372 Marpaung et. al. Science and Technology Indonesia, 8 (2023) 367-372 on the stability of butterfly pea anthocyanins. Therefore, the aim of this study is to investigate the impact of six different chloride salts (NaCl, KCl, CaCl2, MgCl2, FeCl3, and AlCl3) on the stability of butterfly pea flower extract anthocyanins. The UV-Vis spectrophotometer would be employed to monitor the color degradation and change in hue of the extract during storage over a wavelength range of 250-700 nm. 2. EXPERIMENTAL SECTION 2.1 Materials The study utilized fully opened flowers of butterfly pea (Clitoria ternatea L.) sourced from a private plantation in Tangerang, Banten, Indonesia. The petals were carefully separated from the sepals and steam-blanched for 6 minutes (Marpaung et al., 2012) . Various chemical reagents were utilized in the research, including Aluminum Chloride (AnalaR BDH, England), Cal- cium Chloride (Brataco, Indonesia), (Brataco, Indonesia), Iron (III) Chloride (Eterna, Indonesia), Magnesium Chloride (Brat- aco, Indonesia), Potassium Chloride (Brataco, Indonesia), and Sodium Chloride (AnalaR BDH, England). 2.2 Extraction and Addition of Metal Ion The extraction of anthocyanins from butterfly pea (Clitoria ternatea L.) flowers was conducted using a modified version of the previous research (Marpaung et al., 2017) . The extraction process involved mixing 20 grams of the fresh petals with 80 milliliters of deionized water at 60ºC for 30 minutes in the absence of light and under constant agitation. The resulting suspension was then filtered (Filter paper (Whatman 41)), with the filtrate collected and centrifuged at 7,000 revolutions per minute for 5 minutes to separate the pigments. The chloride salts used in this study were NaCl, KCl, CaCl2, MgCl2, FeCl3, and AlCl3, and each had a concentration of 0.025 M. 0.6 mL of the salt solution was added to 1 mL of butterfly pea flower extract, while 0.6 mL of deionized water was added to the control solution. The sample of each extract (2 mL) was placed in a quartz cuvette and then scanned using a UV-Vis spectrophotometer (Genesys 10uv Thermo Electron Corporation, U.S.A.) at a wavelength range of 250 - 700 nm with a 1 nm interval. 2.3 Stability Test Each of the 20 mL sample was repeated twice and placed in a dark vial, then stored in a room that was kept away from light at room temperature. The spectrogram of each sample was scanned with the spectrophotometer at an interval of every two days. The changes in each band in the spectrogram were then analyzed. 2.4 Kinetic Formulation and Statistical Analysis The degradation kinetics of all the bands were evaluated by the first-order reaction. A = A◦.e −kt (1) t0.5 = ln(2)/k (2) A is the final absorbance, A◦ is the initial absorbance, k is the constant of degradation rate (per day), t is the storage time (in days), and t0.5 is the half-life (in days).The trend of the change in absorbance of each band was analyzed using regression anal- ysis, with a significance level of 𝛼 = 0.05. The slope difference between two samples was assessed using a slope test. Both sta- tistical evaluations were conducted using Microsoft Excel® as part of Microsoft 365, which was developed by Microsoft in Redmond, Washington, USA, with a significance level of 𝛼 = 0.05. 3. RESULTS AND DISCUSSION 3.1 The Effect of the Metal Ions on the Spectrogram Six bands appeared in the spectrogram of the aqueous extract of the butterfly pea flower (Figure 1a). The UV region featured three bands, representing benzene derivatives (at ± 265 nm), acyl groups (at ± 310 nm), and non-anthocyanin flavonoids (at ± 350 nm). The visible light region featured three bands of the colored species of anthocyanins, at ± 550 nm representing the red flavylium cation AH+, at ± 574 nm, representing the purple quinonoidal base A, and at ± 617 nm representing the blue anionic quinonoidal base A− (Marpaung et al., 2019) . The addition of monovalent (Na+ and K+) and divalent (Ca2+ and Mg2+) did not give a significant shift in the spectro- gram of the extract (Figure 2b). The absence of the shift caused by the addition of monovalent and divalent metal ions was also observed in various anthocyanin source extracts, such as blueberries (Wang et al., 2010) , red cabbage (Guo et al., 2017) , black peanuts (Shao et al., 2015) , Buniusantidesma (Mustika and Marpaung, 2020) , cyanidin-derived anthocyanin (Sigurdson et al., 2017; Sigurdson et al., 2016), Ribes nigrum (Buchweitz et al., 2013) , dark maize (Mei et al., 2014) , and fungus Pycno- porus sanguineus (Zhang et al., 2019) . In contrast, sodium (Na+) enhances the color of malvidin-derived anthocyanin (Dangles and Brouillard, 1992; Figueiredo and Pina, 1994), potassium (K+) increases the intensity of anthocyanin in red wine (Cz- ibulya et al., 2015) , and calcium (Ca2+) has a color-enhancing effect on blueberry anthocyanin (Li, 2014) and a slight impact on the color of red cabbage anthocyanin (Ratanapoompinyo et al., 2017) . There was also limited evidence of interaction between trivalent metal ions (Al3+ and Fe3+) and the anthocyanins in the butterfly pea flower extract (Figure 1c). The spectrogram of the butterfly pea flower extract added with Al3+ showed only a minor increase in absorbance at ± 550 nm and a slight decrease at ± 617 nm, indicating a possible contribution of Al3+ to the protonation reaction A− ⇌ A ⇌ AH+. A similar outcome was observed in extracts containing Fe3+ ions. Although there was a noticeable shift towards red in hue, it appears to be the same effect exhibited by Al3+, where Fe3+ drove the protonation. Fe3+ had a more intense protonation effect than Al3+. © 2023 The Authors. Page 368 of 372 Marpaung et. al. Science and Technology Indonesia, 8 (2023) 367-372 Figure 1. UV-Vis Light Spectra of Butterfly Pea Flower Aqueous Extract (a), In Divalent Metal Ion (b), and Trivalent Metal Ion Solution (c) Aside from intensifying the red color, Al3+ and Fe3+ also heightened absorption at 420 nm, which reflects yellow-brown color. The average absorption at 420 nm (A420) in the extracts added with trivalent metal ions was ± 0.5, while in other ex- tracts it was ± 0.06. The high A420 significantly increased the browning and decreased the overall color quality of the extract (Cisse et al., 2012) . The reason why metal ions interact with anthocyanins is not known, but the case of butterfly pea flower extract provides a clear understanding. Metal ions typically interact with an- thocyanins via hydroxyl groups on the B-ring. However, the anthocyanins in butterfly pea flowers, the polyacylated antho- cyanins known as ternatins, lack free hydroxyl groups on the B-ring (Kazuma et al., 2003) . Significant changes occurred in the UV region in the ex- tract added with Al3+, including a new band around 380 nm, which appears to be a shift to a longer wavelength from the 350 nm absorption, which is the absorbance of non-anthocyanin flavonoids. This new band indicates the formation of a complex between the non-anthocyanin flavonoid and Al3+. Flavonol glycosides are the most found flavonoids in butterfly pea flow- ers, with kaempferol 3-glycoside being the main compound (Kazuma et al., 2003) . The interaction between kaempferol and Al3+ has been reported recently (Sun et al., 2021) . A significant shift to longer wavelengths was also observed in the UV region of the extract with Fe3+, indicating the poten- tial interaction between Fe3+ and non-anthocyanin phenolic compounds. 3.2 The Effect of the Metal Ions on the Color Stability Dur- ing Storage Scanning of butterfly pea flower extract’s light absorption (250- 700 nm) during storage revealed changes in benzene deriva- tives, acyl groups, non-anthocyanin flavonoids, and antho- cyanins over time (Figure 2). Overall, a degradation of color (A550 + A574 + A617) occurred in all extracts during the 12 days of storage. The rate of color degradation can be modeled by first-order degradation kinetics satisfactorily (p-value of the regression < 0.05). A slope test was carried out with an alpha level of 0.05 to assess the differences in degradation rate be- tween the control extract and extracts containing various metal Figure 2. UV-Vis Spectrogram of Butterfly Pea Flower Aqueous Extract in Various Metal Ion Solutions During 12 Days Storage (a), Control (b), Na+ (c); K+, (d) Ca2+, (e) Mg2+, (f) Al3+, and (g) Fe3+ ions, as seen in Table 1. The test indicated that K+, Mg2+, Ca2+, Al3+ and Fe3+ significantly prolonged the half-life of the flower extract’s color. Meanwhile, Na+ tended to shorten the half-life. Table 1. The Degradation Kinetics (k) and Half-life (t0.5) of the Color of Butterfly Pea Flower Extract in Various Metal Ion Solution Extract R2 p-value k (day-1)* t0.5 (days)* H2O 0.96 <0.01 0.068 10.23b NaCl 0.88 <0.01 0.305 2.27a KCl 0.90 <0.01 0.039 17.72c CaCl2 0.93 <0.01 0.030 23.20d MgCl2 0.79 <0.05 0.026 26.48d AlCl3 0.80 <0.05 0.024 28.91d FeCl3 0.80 <0.05 0.017 41.17e *stated as mean of two replications, different letters above data points indicate significant differences The effect of metal ions on anthocyanin stability is inconsis- tent, with some studies showing a negative effect of Na+ (Chen et al., 2019; de Rosso and Mercadante, 2007; Hubbermann et al., 2006), while others show no effect (Dangles and Brouil- lard, 1992; Figueiredo and Pina, 1994; Peng et al., 2016). The destabilization by Na+ is thought to result from increased solvation of the flavylium cation, leading to dissociation and © 2023 The Authors. Page 369 of 372 Marpaung et. al. Science and Technology Indonesia, 8 (2023) 367-372 Figure 3. Two Possible Pathway of Color Degradation of a Polyacylated Anthocyanin Like Ternatin in Butterfly Pea Flower Extract, (a) the First Way Initiated by the Unfolding of Flavylium Cation (AH+), (b) the Second Way Initiated by the Diacylation of Anionic Quinonoidal base (A−) color loss (Hubbermann et al., 2006) . The positive effect of K+ has been reported (Czibulya et al., 2015) , but differs from other findings (Guo et al., 2017) . The positive effect of Ca2+ observed in this study is consistent with Czibulya et al. (2015) , but differs from other studies that saw no significant impact (Buchweitz et al., 2013; Guo et al., 2017). This study showed a significant positive impact from Mg2+ on anthocyanin stabil- ity. Meanwhile, other studies show that Mg2+ give no effect (Peng et al., 2016; Sigurdson et al., 2016) or even decreased stability (Mei et al., 2014) . Peng et al. (2016) found a negative impact of Fe3+ and a positive impact of Al3+ on anthocyanin stability. The negative impact of Fe3+ was also reported by Guo et al. (2017) and Ratanapoompinyo et al. (2017) . This study supports the improvement of stability by both trivalent metals. In the aqueous system, polyacylated anthocyanins such as ternatins exist in a state of equilibrium between red, purple, and blue species: AH+ ⇌ A ⇌ A−. The hydration of AH+ into the colorless hemiketal B does not occur because it is prevented by the intramolecular copigmentation that forms through the hydrophobic interaction between p-coumaric acid and the anthocyanin molecule (Terahara et al., 1998) . Theoretically, two pathways can cause a polyacylated an- thocyanin to lose its color, as depicted in the scheme in Figure 3 (Marpaung et al., 2017; Marpaung et al., 2019). In the first pathway, the hydrophobic interaction in AH+ undergoes un- folding, causing AH+ to hydrate into B. This reaction disrupts the equilibrium of AH+ ⇌ A ⇌ A− and drives protonation of A → AH+ and A− → A to reach a new equilibrium (Figure 3a). In the second pathway, A− as the least stable species Terahara et al. (1998) is deacylated to A−unacylated, then deprotonated to Aunacylated, and then AH+unacylated, which immediately hydrated to Bunacylated. This series of reactions disrupt the equilibrium of AH+ ⇌ A ⇌ A− (polyacylated) leading to depro- tonation A → A− and AH+ → A (Figure 3b). In the next stage, after the loss of color in anthocyanin, degradation continues to de-glycosylation to anthocyanidin and further degradation to benzaldehyde derivatives and 4-hydroxybenzoic acid (Sun et al., 2011) . The first event of the color loss can be observed in the spec- trogram as a hypochromic shift and the constant or increasing concentration of AH+ relative to A (A550/A574) and the ratio of A− to A (A574/A620). Meanwhile, the second event can be observed as a hypochromic and bathochromic shift, as well as a decrease in A574/A620 and A550/A574. The extract added with Al3+ was the only sample that con- sistently shows an increase in A550/A574 and A574/A620. Con- versely, the extract added with Fe3+ consistently showed a de- crease in A550/A574 and A574/A620, although the bathochromic shift was not clearly visible. Meanwhile, in the control sample and those added with monovalent or divalent ions, there was an increase in A550/A574 and A574/A620 at the beginning of degra- dation, followed by a decrease in both ratios in the subsequent degradation stage. As an addition, a clear bathochromic shift is also seen in the control extract and those added with Na+, K+, and Mg2+ (Figure 2a, 2b, 2c, and 2e).The trend of changes in both ratios suggested that color degradation in the extract added with Al3+ occurred due to the unfolding of hydropho- bic interaction, while in the extract added with Fe3+ the color degradation occurred due to deacylation. Meanwhile, color degradation in the control sample and those added with mono- valent and divalent metal ions occurred due to the unfolding of hydrophobic interaction and followed by deacylation. 3.3 The Effect of the Metal Ions on Benzene Derivatives, Acyl Groups, Non-anthocyanin Flavonoids The light absorption at 265 nm (A265) represents benzene derivatives, including anthocyanins and other flavonoids. Fig- ures 2 clearly shows that the addition of trivalent metal ions inhibited the degradation of benzene derivatives. With a first- order degradation kinetics model (p-value), the degradation rate (k) of A265 in the extract added with Al3+ or Fe3+ was significantly lower compared to the k in other extracts. In line with the degradation of colored anthocyanins, the stability of benzene derivatives in the extract added with Na+ was lower compared to the control extract. However, there was no signif- icant difference in the stability of benzene derivatives between the control extract and those added with K+, Ca2+, and Mg2+. The evolution of light absorption at 310 nm (A310), which represents the acyl group, offered compelling evidence in sup- port of the hypothesis regarding the mechanisms of antho- cyanin degradation. The exponential regression analysis (1st order degradation kinetics) revealed that degradation of A310 in the extract added with Al3+ was the only one that was not statistically significant (p > 0.05). This supported the notion that deacylation did not occur in the extract containing Al3+, thereby reinforcing the idea that the degradation of colored anthocyanins in this sample was a result of the unfolding of hydrophobic interaction. The fact that degradation of A310 was not significant and the degradation rate of A265 in the extract containing Al3+ was low suggests that the color degradation in this extract has only © 2023 The Authors. Page 370 of 372 Marpaung et. al. Science and Technology Indonesia, 8 (2023) 367-372 reached the stage of transforming colored ternatin species into a reversible colorless one. There had not been any chemical degradation of the ternatins to unacylated anthocyanin and further to anthocyanidin, etc. The extract added with Al3+ is also the only sample that did not experience significant degradation of non-anthocyanin flavonoids (A350 and A380). It seemed that Al3+ successfully formed a stable complex with the non-anthocyanin flavonoids in the butterfly pea extract. Whether there is a connection between the stability of this complex and the inhibition of deacylation in butterfly pea flower anthocyanin, further study is needed. 4. CONCLUSION Scanning the UV-Vis spectrophotometer at the wavelength range of 250-700 nm on the butterfly pea flower extract in var- ious metal ion solutions during storage has provided a broader perspective on how color degradation occurs. K+, Ca2+, Mg2+, Al3+, and Fe3+ ions showed the ability to improve the stability of the butterfly pea flower extract color, while Na+ tended to accelerate color degradation. The pattern of changes in the extract spectrogram during storage suggests that the color degradation of the extract pro- ceeds through two mechanisms: the unfolding of hydrophobic interactions that establish the intramolecular copigmentation between ternatin and p-coumaric acid, and the deacylation of ternatin. Trivalent metal ions showed the best stability per- formance. Fe3+ prevented the unfolding of the hydrophobic interaction, while Al3+ hindered the occurrence of deacylation. The combination of the two is highly likely to improve the color stability of the butterfly pea flower extract. However, both in- crease the browning index, thus decreasing color quality. This research highlights that the addition of cations is a potential method for improving the color stability of the butterfly pea flower extract, making it a more attractive food coloring agent. 5. ACKNOWLEDGMENT The authors would like to express their gratitude to the Faculty of Life Sciences and Technology at Swiss German University for providing the necessary laboratory facilities to conduct this research. We greatly appreciate the support and resources provided by the faculty, which enabled us to carry out our experiments and collect valuable data. REFERENCES Buchweitz, M., M. Speth, D. Kammerer, and R. Carle (2013). Impact of Pectin Type on the Storage Stability of Black Currant (Ribes nigrum L.) Anthocyanins in Pectic Model Solutions. Food Chemistry, 139(1-4); 1168–1178 Chen, W., E. Karangwa, J. Yu, S. Xia, B. Feng, and X. Zhang (2019). Effect of Sodium Chloride Concentration on Off- flavor Removal Correlated to Glucosinolate Degradation and Red Radish Anthocyanin Stability. Journal of Food Science and Technology, 56; 937–950 Cisse, M., F. Vaillant, A. Kane, O. Ndiaye, and M. Dornier (2012). Impact of the Extraction Procedure on the Kinetics of Anthocyanin and Colour Degradation of Roselle Extracts During Storage. Journal of the Science of Food and Agriculture, 92(6); 1214–1221 Czibulya, Z., I. Horváth, L. Kollár, M. P. Nikfardjam, and S. Kunsági-Máté (2015). The Effect of Temperature, pH, and Ionic Strength on Color Stability of Red Wine. Tetrahe- dron, 71(20); 3027–3031 Dangles, O. and R. Brouillard (1992). Polyphenol Interac- tions the Copigmentation Case: Thermodynamic Data From Temperature Variation and Relaxation Kinetics Medium Ef- fect. Canadian Journal of Chemistry, 70(8); 2174–2189 de Rosso, V. V. and A. Z. Mercadante (2007). Evaluation of Colour and Stability of Anthocyanins From Tropical Fruits in an Isotonic Soft Drink System. Innovative Food Science & Emerging Technologies, 8(3); 347–352 Figueiredo, P. and F. Pina (1994). Formation of Anthocyanin Ion-pairs. A Co-pigmentation Effect. Journal of the Chemical Society, Perkin Transactions 2, 2(4); 775–778 Guo, S., W. Zhang, and Y. Lv (2017). Effect of Metal Ions on the Color Stability of Anthocyanins From Purple Cabbage. China Condiment, 42(6); 152–158 Hubbermann, E. M., A. Heins, H. Stöckmann, and K. Schwarz (2006). Influence of Acids, Salt, Sugars and Hydrocolloids on the Colour Stability of Anthocyanin Rich Black Currant and Elderberry Concentrates. European Food Research and Technology, 223; 83–90 Kazuma, K., N. Noda, and M. Suzuki (2003). Flavonoid Com- position Related to Petal Color in Different Lines of Clitoria Ternatea. Phytochemistry, 64(6); 1133–1139 Li, M. C. L. Y. . L. C., Y. (2014). Study on the Stability of Anthocyanins of Raspberry. Science and Technology of Food Industry, 10; 205–208 Marpaung, A., N. Andarwulan, and E. Prangdimurti (2012). The Optimization of Anthocyanin Pigment Extraction From Butterfly Pea (Clitoria ternatea L.) Petal Using Response Surface Methodology. Acta Horticulturae, 1011; 205–211 Marpaung, A. M., N. Andarwulan, P. Hariyadi, and D. N. Fari- dah (2019). The Difference in Colour Shifting of Clitoria ternatea L. Flower Extract at pH 1, 4, and 7 During Storage. Current Nutrition & Food Science, 15(7); 694–699 Marpaung, A. M., N. Andarwulan, P. Hariyadi, and D. Nur Faridah (2017). The Colour Degradation of Anthocyanin-rich Extract From Butterfly Pea (Clitoria Ter- natea L.) Petal In Various Solvents at pH 7. Natural Product Research, 31(19); 2273–2280 Maylinda, E. V., A. Rinadi, E. Putri, G. Fadillah, and S. Wayun- ingsih (2019). Color Stability of Anthocyanins Copigmenta- tion From Red Rice (Oryza sativa L.) Bran by Spectropho- tometry Uv-Vis. IOP Conference Series: Materials Science and Engineering, 578(1); 012001 Mei, X., H. Qin, J. Wang, G. Wang, C. Liu, and Y. Cai (2014). Studies on Physicochemical Characteristics of Anthocyanin From Super Dark Maize. Journal of Food and Nutrition Re- © 2023 The Authors. Page 371 of 372 Marpaung et. al. Science and Technology Indonesia, 8 (2023) 367-372 search, 2(3); 109–114 Mustika, S. R. and A. M. Marpaung (2020). Color Properties and Stabilizing Effect of Metal Ion on Anthocyanin from Buni (Antidesma bunius) Fruit. Advance in Engineering Re- search; 5th International Conference on Food, Agriculture and Natural Resources, 194(1); 223–225 Peng, K., C. Liu, and S. Wang (2016). Study on Stability of Anthocyanin From Blueberry Peel. American Society of Agri- cultural and Biological Engineers Annual International Meeting, 2016; 1 Ratanapoompinyo, J., L. T. Nguyen, L. Devkota, and P. Shrestha (2017). The Effects of Selected Metal Ions on the Stability of Red Cabbage Anthocyanins and Total Phenolic Compounds Subjected to Encapsulation Process. Journal of Food Processing and Preservation, 41(6); 13234 Ren, E., C. Li, J. Sun, L. Li, B. Zheng, J. Li, G. Liu, and J. Sheng (2014). Effects of Metal Ions and Food Additives on Stability of Anthocyanins From Mulberry. Journal of Southern Agriculture, 45(1); 98–103 Shao, Y., X. L. Liu, H. Shao, and Y. J. Li (2015). Research on the Stability and Content Detection of Anthocyanin of Black Peanuts Clothing. Advanced Materials Research, 1090; 123–129 Sigurdson, G., R. Robbins, T. Collins, and M. Giusti (2017). Spectral and Colorimetric Characteristics of Metal Chelates of Acylated Cyanidin Derivatives. Food Chemistry, 221; 1088–1095 Sigurdson, G. T., R. Robbins, T. Collins, and M. Giusti (2016). Evaluating the Role of Metal Ions in the Bathochromic and Hyperchromic Responses of Cyanidin Derivatives in Acidic and Alkaline pH. Food Chemistry, 208; 26–34 Sun, J., W. Bai, Y. Zhang, X. Liao, and X. Hu (2011). Identifi- cation of Degradation Pathways and Products of Cyanidin-3- sophoroside Exposed to Pulsed Electric Field. FoodChemistry, 126(3); 1203–1210 Sun, L., X. Wang, J. Shi, S. Yang, and L. Xu (2021). Kaempferol as an AIE-active Natural Product Probe for Selective Al3+ Detection in Arabidopsis Thaliana. Spec- trochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 249; 119303 Terahara, N., K. Toki, N. Saito, T. Honda, T. Matsui, and Y. Osajima (1998). Eight New Anthocyanins, Ternatins C1- C5 and D3 and Preternatins A3 and C4 from Young Clitoria t ernatea Flowers. JournalofNaturalProducts, 61(11); 1361–1367 Wang, B. C., R. He, and Z. M. Li (2010). The Stability and Antioxidant Activity of Anthocyanins From Blueberry. Food Technology and Biotechnology, 48(1); 42–49 Zhang, H., X. Gao, X. Guo, A. Kurakov, and F. Song (2019). Stability Study of the Pigment Extract From A Wild Pycno- porus sanguineus. International Journal of Microbiology and Biotechnology, 4; 121–127 © 2023 The Authors. Page 372 of 372 INTRODUCTION EXPERIMENTAL SECTION Materials Extraction and Addition of Metal Ion Stability Test Kinetic Formulation and Statistical Analysis RESULTS AND DISCUSSION The Effect of the Metal Ions on the Spectrogram The Effect of the Metal Ions on the Color Stability During Storage The Effect of the Metal Ions on Benzene Derivatives, Acyl Groups, Non-anthocyanin Flavonoids CONCLUSION ACKNOWLEDGMENT