*4.1.3 Dilute acid treatment*

Sulfuric acid solution (1% w/v) was applied with different temperatures (100, 140, and 180°C) and times (0, 30, and 60 min) in 101SSHPR2 reactor warmed up in an oil bath. In order to extract pectin, the optimal acid treatment condition was encountered at 94°C for 60 min with 140 mL of sulfuric acid (1% w/v) and 10 g of loaded orange peel/pulp in the reactor. Then, the temperature was quickly decreased using an ice bath. The suspension was filtered for the solid residues that rinsed with distilled water to remove chemicals. Then, they were freeze-dried and kept at room temperature, but the liquid fraction was kept at −20°C for pectin extraction and purification.
