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Investigation of stability of colorant powders extracting from Japanese purple sweet potato (Ipomoea batatas (L.) Poir)

To avoid denaturation of anthocyanin content, the pigment should be stored in the dark and at low temperature (10 °C). The acidic media could preserve the colorant powder by protecting anthocyanins, but it reduced the biological property of the pigment. | 28 SCIENCE & TECHNOLOGY DEVELOPMENT JOURNAL, Vol 20, No.K7- 2017 Investigation of stability of colorant powders extracting from Japanese purple sweet potato (Ipomoea batatas (L.) Poir) Phan Nguyen Quynh Anh, Le Thi Hong Nhan Abstract — The stability of colorant powders from Japanese purple sweet potato (Ipomoea batatas (L.) Poir) harvested in Vinh Long province was investigated. The colorants were formed from extracting solutions which were adjusted to pH of 6, 5, 4 and 3 before converted to powder matrix. They had red-purple color and contained anthocyanin concentration of about 32 mg/g. The IC50 inhibitory concentration of the neutral powder was 292.7 µg/mL, whereas the IC50 of pH3 powder was 484 µg/mL, which antioxidant activity decreased by increasing of acidic media clearly. Stability of appearance colors, anthocyanin content, polyanthocyanin index and antioxidant capacity were investigated and they depended on storing conditions (temperature and radiation) and pH media. To avoid denaturation of anthocyanin content, the pigment should be stored in the dark and at low temperature (10 °C). The acidic media could preserve the colorant powder by protecting anthocyanins, but it reduced the biological property of the pigment. Index Terms — purple sweet potato, anthocyanin, stability, antioxidant. N 1 INTRODUCTION owadays, the demand for natural colors is increasing very much due to the increased awareness of therapeutic and medicinal properties and their benefits of them. Anthocyanin is one of natural coloring agents which are quite common, Manuscript Received on October 17th, 2016, Manuscript Revised April 07th, 2017 This research is funded by Ho Chi Minh City University of Technology –VNU-HCM, under grand number T-KTHH-201650. Phan Nguyen Quynh Anh, Le Thi Hong Nhan – Ho Chi Minh City University of Technology, VNU-HCM. Email: pnqanh@hcmut.edu.vn soluble in water and found in red/purplish fruits and vegetables. Anthocyanin pigments take their color from the