Effects of various clarification treatments on anthocyanins, color, phenolics and antioxidant activity of red grape juice.

Low turbidity and low discolouration is targeted in clear red grape juice (RGJ) production. Depending on type of clarification agents, substantial discolouration may occur. Therefore, this study was undertaken to show effects of various clarification treatments (bentonite and chitosan, and combinations of "bentonite + gelatin (B + G)," "bentonite + casein (B + CA)," "bentonite + albumin (B + A)" and "bentonite + chitosan (B + CTS)" on turbidity, color (ACNs, color density-CD and polymeric color-PC), phenolics and antioxidant activity (AOA) during RGJ clarification. Casein alone (4.0 NTU and 9.1% ACN loss) and in combination with bentonite (4.4 NTU and 12.3% ACN loss), followed by B + A (5.7 NTU and 12.3% ACN loss) resulted in best clarity and was associated with least change in ACNs. These clarifications also resulted in high CD (intensive red color) and low PC (low browning). At all dosages, gelatin and albumin were associated with highest ACN losses, while casein in greatest retention. "Bentonite + casein," followed by "bentonite + albumin," achieved the best clarification of RGJ.