The purpose of this work was to establish the best particle size for recovering high yields of total phenolic compounds (TPC), total anthocyanin compounds(TAC) and total flavonoid compounds (TFC) from roselle (Hibiscus sabdariffa) by applying supercritical carbon dioxide (ScCO₂). The extraction rate, diffusivity and solubility of yield in ScCO₂ were also studied and calculated utilizing models. Pressure (10 and 30 MPa), temperature (40 and 60 °C), and particle size (250 µm < dp < 355 µm, 355 µm < dp < 425 µm and 425 µm < dp < 500 µm) were employed as variables in this experiment. The greatest recovery was 11.96% yield, 7.16 mg/100 g TAC, 42.93 mg/100 g TPC and 239.36 mg/100 g TFC under the conditions of 30 MPA, 40 °C and 250 µm < dp < 355 µm, respectively. The extraction rate of supercritical carbon dioxide in roselle extraction ranged from 5.19 E−03 to 1.35 E−03 mg/s fitted using the Esquivel model. The diffusivity coefficient of ScCO₂ ranged from 2.17E−12 to 3.72E−11 mg/s², as fitted by a single sphere model. The greatest solubility of global yield, TAC, TPC and TFC in ScCO₂ was 1.50 g/L, 0.3 mg/L, 1.69 mg/L and 9.97 mg/L, respectively, with a particle size of 250 µm < dp < 355 µm. The smaller particle size of roselle provides the maximum bioactive compound recovery and solubility. Furthermore, the diffusivity and extraction of ScCO₂ are increased by decreasing the particle size. Therefore, a smaller particle size is appropriate for roselle extraction by ScCO₂ based on the experimental and modelling data.

The dumping of waste banana peels from local chip manufacturing has encouraged sustainable food trends to valorize these peels as pectin sources. In this study, soluble pectin from banana peels was extracted using a continuous subcritical water extraction system (SWE). This method was a promising fast extraction process with a water solvent that was environmentally friendly. Temperature (100 to 160 °C) and extraction time (5 to 50 minutes) were manipulated, with a fixed pressure of 15 MPa, a flow rate of 15 mL/min, and a particle size of 0.6 mm. The response surface methodology (RSM) was used to generate approximately 13 experimental trials from the central composite design. Based on linear and square models, the results revealed that the interaction of temperature and time to pectin yield had a significant effect. At 100°C for 5 minutes, an optimal condition for producing pectin yield was achieved, which risen the highest pectin yield by 26%. As a result, the SWE continuous system promoted increased pectin production in the shortest extraction time. In short, banana peel pectin is a powder that serves a primary function in numerous food, pharmaceutical, and cosmeceutical applications.