Anthocyanin stability of mixed fruit juice consisting of pomegranate and orange enriched with amino acids during storage

In this study, effects of various amino acids (aspartic acid, phenylalanine, valine, asparagine ve lysine) and various pomegranate juice (PJ):orange juice (OJ) ratios on storage stability of single-strenght and concentrated PJ anthocyanins are investigated. Identification of L-ascorbic acid, anthocyanin and amino acids were carried out by HPLC methods. In concentrated PJ, aspartic acid and asparagine had the highest copigmentation effect, while only asparagine showed copigmentation effect in the presence of L-ascorbic acid in PJ obtained from PJC:orange juice mixture. Strong correlation between color density and hyperchromic effect(Amax) values (r= 0.735–0.995 and r= 0.729–0.964, respectively) during storage at –25°C (0 and 9th months) proved copigmentation. After 18 months, pomegranate anthocyanins were polymerized. Increase in total monomeric anthocyanin(TMA) stability, Amax and color density values (5.13%, 4.71% and 4.20%) in PJs showed that only aspartic acid showed copigmentation effect. At different PJ:OJ ratios (100:0, 75:25 and 50:50), aspartic acid increased TMA, Amax and color density stability in only 50:50 PJ:OJ sample (9.20%, 6.42% and 16.55%, respectively) during storage. Strong correlations between Amax-color density and Amax-anthocyanin interactions (r= 0.816–0.982 and r= 0.812–0.981, respectively) proved that copigmentation occurred during storage. In both single-strenght PJ and PJ obtained form PJC:OJ mixtures, with the addition of OJ, Amax values increased in all samples only at the beginning of storage (21.34%). However, this increase did not continue throughout storage. In addition, amino acids added in single-strenght PJ, PJ obtained form PJC and also PJ:OJ mixtures did not show a systematic change during storage.