Abstract

Effects of pH, sugars, organic acids, metal ions, ascorbic acid and light on the stability of anthocyanin pigment extracted from purple-fleshed potato (Solanum tuberosum L.) were studied. The pH had marked influences on the color of the potato anthocyanin pigment: i.e., the lower the pH of the anthocyanin solution was, the more stable and intenser of the pigment was. It showed characteristic bathochromic shift as the pH of the solution increased. Generally, the addition of sugars into the purple-fleshed potato anthocyanin solution caused decrease in color stability of the pigment. Among the sugars tested, maltose was the most deleterious followed by sucrose, galactose, fructose and glucose. The addition of organic acids greatly increased the stability of the pigment. Malic acid was found to be the most effective in stabilizing the pigment followed by tartaric, citric and succinic acids, while malonic acid was found to be deteriorative to the stability of the pigment. Most metal ions except $Cu^{2+}$ increased stability of the pigment-especially, $Cd^{2+}\;and\;Al^{3+}$ were more effective than the others. Ascorbic acid degraded the pigment considerably, but the adverse effect was diminished by adding thiourea. Light gave an adverse effect to the stability of the purple-fleshed potato anthocyanin pigment, which could be minimized by shielding the light from the pigment.

자색감자의 anthocyanin 색소의 안정성에 대한 pH, 당, 유기산, 금속이온, ascorbic acid 및 광의 영향을 조사하였다. 자색감자 색소는 pH가 낮을수록 anthocyanin 색소의 안정성이 증가하였으며 pH가 높아질수록 색소 용액의 최대흡수파장이 장파장 쪽으로 이동하는 bathochromic shift현상이 관찰되었다. 당류 첨가는 오히려 무첨가구에 비해서 저장 안정성을 저하시켰는데 maltose, sucrose, galactose, fructose, glucose 순으로 안정성이 저하되었다. 유기산은 anthocyanin 색소의 안정화에 크게 기여하였으며 그 순서로는 malic acid, tartaric acid, citric acid, succinic acid 순으로 나타났고 malonic acid는 오히려 안정성을 떨어뜨렸다. 금속이온은 $Cu^{2+}$을 제외하고는 anthocyanin 색소의 안정화에 기여하였으며 특히 $Cd^{2+},\;Al^{3+}$이 효과적이었다. Ascorbic acid는 anthocyanin 색소의 파괴를 초래하여 안정성을 저하시켰으나 thiourea를 첨가하므로 색소파괴의 정도를 낮출 수 있었다. 일광에 의해 anthocyanin 색소의 파괴가 촉진된 반면 광을 차단할 경우 색소를 안정화시킬 수 있었다.

Keywords

• purple-fleshed potato;
• anthocyanin;
• color stability