Pilot-scale subcritical water extraction of flavonoids from satsuma mandarin (Citrus unshiu Markovich) peel

•Pilot-scale subcritical water extraction was conducted to extract antioxidant flavonoids from agricultural by-products.•The extraction efficiency of the constructed pilot-scale extractor was good enough.•Large-scale experiments using this subcritical water extraction method demonstrate its potential industrial application.

The effects of operating parameters (extraction temperature, extraction time, material type, solute/solvent ratio, and pressure) on the subcritical water extraction of flavonoids from dried satsuma mandarin peel were studied. From the practical aspect, the optimum conditions for obtaining flavonoids by pilot-scale subcritical water extraction were as follows: extraction temperature of 130 °C, extraction time of 15 min, and solute/solvent ratio of 1/34. The yields of flavonoids obtained under laboratory and pilot conditions were similar: 117.8 and 113.4 mg/g satsuma mandarin peel, respectively. The proportion of flavonoids recovered by subcritical water extraction in the pilot plant was 96.3%, and large-scale experiments using this method demonstrate its potential industrial applications.Industrial relevanceThis study used a pilot-scale subcritical water extraction (SWE) plant (8 L scale) for the scale-up and commercialization of the SWE process that extracts antioxidant flavonoids from agricultural by-products such as Citrus unshiu Markovich. SWE is excellent technology to selectively extract flavonoids using temperature-dependent dielectric constant properties of water. The flavonoid yield from the pilot-scale SWE was similar to that obtained from laboratory-scale SWE. These results indicate that SWE is an efficient and rapid method for extracting flavonoids, and a safer product only using purified water. This method can be easily implemented on an industrial scale.