Optimization and valorization of Citrus reticulata 'Chazhi' pulp waste for citric acid recovery and juice beverage development

The dried pericarp of Citrus reticulata 'Chachi' (CRC) is widely utilized, but over 80% of its pulp is discarded, wasting citric acid and causing environmental risks. In this study, HPLC analysis showed that July CRC pulp had the highest citric acid content (31.66 mg/mL). These pulp were therefore selected as raw materials. We then optimized two extraction methods. For the calcium salt method, optimal conditions were 97°C, 411s, and pH 9.7. It yielded 62.11 g/hg citric acid with a purity of 76.23 g/hg. For the ion exchange method, D311 resin was chosen. Optimal conditions included a sample loading flow rate of 10 mL/min, 0.5 mol/L sodium hydroxide eluent, and an elution flow rate of 4 mL/min. This method achieved an extraction rate of 32.13 g/hg and a purity of 75.59 g/hg. Moreover, a pulp juice beverage compounded with sugarcane was developed with the following optimized parameters: total juice content of 50 mL/dL, CRC-to-sugarcane ratio of 1.5:1 (v/v), and 0.07 g/mL added sucrose. In conclusion, this study offers key insights into tackling CRC pulp resource waste. Unlocking its potential for citric acid products and juices, the research enhances resource recycling efficiency and delivers economic and environmental benefits. • Citric acid in Citrus reticulata 'Chazhi' pulp peaks in July (31.66 mg/mL). • The calcium salt method affords relatively high citric acid yield and purity. • C. reticulata 'Chazhi' exhibit potential for compound juice development. • Waste can be converted into valuable resources for pharmaceutical and food fields.