Influence of sugars and chlorogenic acid addition on anthocyanins of blackberry juice

In this study influence of addition of sugars and chlorogenic acid on anthocyanin stability in blackberry juice during storage (65 days at 4°C) was investigated. Samples of juice were prepared with addition of 10% of sugars (sucrose, fructose, glucose and trehalose), with addition of chlorogenic acid (pigment:copigment molar ratio 1:50) and with addition of both chlorogenic acid and sugars. Control sample was juice without additives. Copigmentation effect is well known tool for improving anthocyanin stability, so investigation of both influence of copigmentation and sugar addition on anthocyanins was conducted. Samples were investigated for their anthocyanin content (AC), polyphenol content (PC), antioxidant activity (AA) and color change (ΔE*). After preparation samples were left for 48 hours to stabilize and all parameters were determined. After stabilization, positive influence of trehalose and glucose addition (175.34 and 174.71 mg/1000 mL, respectively) on AC was observed, while samples with sucrose and fructose had lower AC (172.46 and 172.21 mg/1000 mL, respectively) than control sample (173.21 mg/1000 mL). During storage AC decreased but the same tendency remained. Addition of chlorogenic acid caused increase of AC (175.84 mg/1000 mL) due to copigmentation effect. In some cases copimentation effect was enhanced with addition of sugars, like in the case of glucose and trehalose (176.72 and 179.47 mg/1000 mL, respectively), and that tendency was observed also during storage. Addition of sucrose and fructose didn’t have the same effect on copigmentation, so improvement of anthocyanin stability wasn’t observed. During storage both PC and AA decreased. The highest ΔE* during storage was observed for samples with sugar addition when trehalose was added (1.06), and when chlorogenic acid was added for samples without sugars addition (0.98). Our results could be explained with interactions that occurred in samples, between anthocyanins, sugars and chlorogenic acid, in which type of sugars played an important role.