Effect of combined drying method on phytochemical components, antioxidant capacity and hygroscopicity of Huyou (Citrus changshanensis) fruit

Abstract Huyou fruit is mainly consumed in fresh form. The saturation of the fresh food market and the lack of deep processing research have caused a huge quantity of Huyou fruits to be wasted due to spoilage. In this study, microwave vacuum drying (MVD) was combined with freeze-drying (FD) to study the effect of drying processing on Huyou quality. MVD was used as pre-drying (MVD-FD), post-drying (FD-MVD) or pre-drying as well as post-drying (MVD-FD-MVD) of FD to process Huyou fruit. The drying characteristic, phytochemicals content, antioxidant activity, color, absorption behavior and hygroscopicity were evaluated as affected by drying conditions. The results showed that the combined drying in all cases significantly shortened the drying time of FD. FD samples had the highest content of reducing sugar and carotenoids. FD-MVD gave significant advantages in increasing the total phenol content and flavonoid content of Huyou extracts, which presented the highest antioxidant activity (based on the evaluation of DPPH scavenging activity and ferric reducing antioxidant potential). In terms of color, MVD-FD samples had good color as the FD samples. All dried samples exhibited similar moisture adsorption behavior. MVD-FD was the best in terms of the overall effect of maintaining product quality and reducing hygroscopicity when compared with FD and MVD.