Potentially Functional Apple Snacks Infused in the Hibiscus sabdariffa Extract Obtained by Convective and Infrared Drying: Kinetics of Drying and Phytochemical Analysis

Abstract

Apple snacks were obtained by using convective air (CD) and infrared drying (IR). The apple slices were immersed in Hibiscus sabdariffa aqueous extract for 30 min, followed by drying at temperatures varying between 50°C and 70°C. The kinetics of drying data were analyzed based on higher values of R² and lower SSR values and fitted to the Page model. The effective moisture diffusivity was higher for infused samples. The color of the infused sample increases, whereas the other colorimetric indices denote the appearance of enzymatic and non-enzymatic browning. The browning index indicated a combined inhibitory effect of Hibiscus extract and temperature, up to 70°C, on oxidative enzymes. Regardless of the drying method, the infused samples showed significantly lower firmness and increased crispness. The rehydration and shrinkage ratio showed the highest value after 5 min of drying at 70°C, with higher values for IR. Color was highly appreciated for the infused variants, with the highest overall acceptability scores for the variants obtained by drying at 70°C. The antioxidant activity of all samples showed no statistically significant differences (p < 0.05), with the highest value of 3.19 ± 0.03 mMol/g DW for the infused samples dried by CD at 50°C. Cafestol was the main compound found in all samples; moreover, the infused samples showed higher values for bioactive compounds due to the extract's contribution to the polyphenolic profile of the samples. The potentially functional properties of the infused apple snacks were appreciated based on the phytochemical profile, antioxidant activity, color, and textural properties.