Effects of Pretreatment and Drying on Composition and Bitterness of High-Dietary-Fiber Powder from Lime Residues

Lime residues after juice extraction were used as a starting raw material to produce high-dietary-fiber powder. The effects of pretreatment—i.e., blanching and ethanol soaking (55–95% v/v)—and hot air drying at 60–100°C on the proximate composition and limonin, a substance responsible for bitterness in citrus fruits, were evaluated. Hydration properties—i.e., water retention capacity and swelling capacity—and visual color were also determined. It was found that using selected pretreatments in combination with the drying process caused significant effects on dietary fiber contents and visual color. The higher reduction in limonin contents was observed for the samples having subjected to higher ethanol concentration and higher drying temperature. Blanching and ethanolic pretreatment also improved the water retention and swelling properties of the final product.