Conversion of 6-gingerol to 6-shogaol in ginger (Zingiber officinale) pulp and peel during subcritical water extraction

Subcritical water extraction is an eco-friendly method for the extraction of less polar compounds without the use of organic solvents. This study determined the extraction conditions that maximize the contents of 6-gingerol and 6-shogaol obtained from ginger pulp and peel. The highest yields of 6-gingerol (0.68 ± 0.08 mg/g), and 6-shogaol (0.39 ± 0.03 mg/g) were obtained from ginger pulp at the extraction conditions of 130 °C/25 min, and 190 °C/15 min. 6-Shogaol content increased with the increasing extraction temperature and extraction time due to the conversion of 6-gingerol to 6-shogaol by thermal cracking. The antioxidant activity of ginger extracts were increased depending on the increasing of 6-shogaol content.