Stability of bioactive compounds of sea buckthorn juices and nectar under different storage conditions
M. Netzel1, G. Strass1,2, S. Allmann1, K. Kranl1, I. Bitsch2, R. Bitsch1
1Institute of Nutrition, Friedrich-Schiller-University of Jena, Jena, Germany
2Institute of Nutrition, Justus-Liebig-University of Giessen, Giessen, Germany
The present study was designed to determine the effects of different storage conditions on the antioxidant capacity and stability of bioactive compounds in sea buckthorn juices (3) and nectar (1). The hydrophilic antioxidant capacity was measured with the TEAC assay and the bioactive compounds were determined by HPLC-DAD (ascorbic acid, isorhamnetin-3-rutinoside and isorhamnetin-3-glucoside) and photometrically (total polyphenols) once a week over a period of 4 weeks. The juices/ nectar were stored under the following conditions: A1 (opened bottles at room temperature [darkness; 22°C]); A2 (opened bottles at room temperature including an UV-light exposure of 10 min/ week); B1 (opened bottles in the refrigerator [darkness; 5°C]); B2 (opened bottles in the refrigerator including an UV-light exposure of 10 min/ week). Between 60% and 91 % of the original hydrophilic antioxidant capacity remained in the juices/ nectar after 4 weeks of storage under the described conditions. The decrease of antioxidant capacity is probably due to the decreased content of ascorbic acid and total phenols. 63 % of the ascorbic acid was destructed in 4 weeks, but only 27 % of the total phenol content. In contrast to the total phenols, the stabilities of isorhamnetin-3-glucoside and isorhamnetin-3-rutinoside, as the major flavonoid-compounds in sea buckthorn, were high and very similar (losses between 1 and 16% for both flavonoid-glycosides). Interestingly, no significant differences could be observed between the juices and the nectar as well as between the different storage conditions regarding the investigated parameters. Further studies on storage conditions affecting the antioxidant capacity and bioactive compounds in sea buckthorn products are in preparation.