Optimisation of the clarification of kiwifruit juice with tannic acid-modified chitosan

Chitosan (CS) is an effective clarifying agent for fruit juice. However, its low antioxidant ability is a limitation in preserving the antioxidant capacity of the juice during clarification. In this work, an antioxidant CS derivative, tannic acid-modified CS (TA-CS), was used as a clarifying agent to optimise the clarification of kiwifruit juice. By using response surface methodology and the transmittance of the juice as a response, the optimal clarification conditions were obtained as follows: TA-CS concentration of 600 μg mL-1, juice pH of 3.5, and heating temperature of 70 °C. Under the optimal conditions, TA-CS showed an excellent clarification effect on kiwifruit juice, which was confirmed by the high transmittance of 99.3%. Meanwhile, the retention rate of vitamin C in the juice reached 97.0% for the TA-CS treatment, being significantly higher than that for the CS treatment. Our results suggest that TA-CS may be a promising clarifying agent for the production of fruit juice.