Matrix-Dependent Effects of Convective Drying on Bioactive Compounds and Pigment Stability in Rose Hip and Blackcurrant

Rose hip and blackcurrant contain bioactive compounds that may respond differently to thermal processing. This study evaluated the effect of convective hot-air drying on bioactive compounds, antiradical power, pigments, and surface color in wild rose hip (Rosa eglanteria) and blackcurrant cv. Silvergrietten. Rose hip fruits received three equatorial punctures before drying to facilitate moisture transfer. Fruits were dried at 70 °C and an air velocity of 3 m/s to final moisture contents of 9% and 12%, respectively, then milled and sieved through an 18-mesh screen. Composition data were compared on a dry-matter basis. Total phenolics were determined using Fast Blue BB because of the high ascorbic acid content of these matrices. Determinations were performed in triplicate, and means were compared by ANOVA and the DGC test (p ≤ 0.05). Drying increased measured total phenolics, flavonoids, and antiradical power by 25%, 29%, and 14%, respectively, in rose hip, and by 19%, 17%, and 21% in blackcurrant. Conversely, ascorbic acid decreased by 27% and 29%, respectively. Rose hip carotenoids showed 99.7% retention, whereas blackcurrant monomeric anthocyanins decreased by 45%. Rose hip powder was yellowish-orange and exhibited a greater overall color difference from fresh fruit than purple-reddish blackcurrant powder. Thus, convective drying increased measured phenolic, flavonoid, and antiradical values, while causing significant ascorbic acid losses and matrix-dependent pigment responses. These findings support matrix-specific optimization of drying conditions according to the compounds targeted for preservation in each fruit.