Stability Research of Color Value during Processing of Concentrated Apple Juice

Apple fruits with varieties of Fuji and Qinguan used for apple juice processing were chosen in this study. Coupled effect of pectinase (PA and PP) on the stability of color value as well as ultrafiltration membrane flux and resin running time were investigated. Compared with PA treatment, PA coupled with PP could significantly improve the color value of apple juice after ultrafiltration and filling processing. The optimal conditions were as follows:Suitable addition concentration of PA 25 mL/t, PP 10 mL/t, enzymolysis time 60 min. Under this condition, the color value (T₄₄₀,%) was increased 2.2% after ultrafiltration, and the difference of color value before and after filling was reduced to 3% Daily color browning index was decreased to 0.05%. Moreover, both ultrafiltration flux and resin running time were increased over 10%. It indicated that PA coupled with PP treatment could be an efficient technique to improve the stability of color value during processing of concentrated apple juice.