Effects of Different Pretreatments With Vacuum Drying on Drying Kinetics, Bioactive Properties and Physicochemical Characterization of Red Beetroot Snacks

ABSTRACT

Innovative approaches for developing nutritious and healthier snack options from vegetable sources have become increasingly important due to modern dietary patterns and growing health concerns. This study aimed to evaluate the effects of various pretreatments (freezing [FP], infrared [IP], microwave [MWP], and ultrasound [USP]) on the vacuum drying kinetics, bioactive and physicochemical properties of red beetroot snacks. MWP significantly shortened the drying time to 290 min. The Sigmoid and Cubic equations were the best describing drying models. The highest D _eff was 2.52 × 10 ⁻⁸  m ² /s in MWP. While USP provided the highest betalain content (8503.22 mg/kg), FP had the lowest value (3162.43 mg/kg). Betanin, isobetanin and vulgaxanthin I as betalain compounds were identified. MWP had the highest total phenolic content (6402.93 mg/kg), and the highest antioxidant activity (59.38%) was found in NP (no pretreatment). Dried red beetroots had softer texture for both pretreatments. All samples showed porous structures except for NP and FP. FP affected thermal behavior and functional groups of samples. Results showed that USP and MWP for vacuum drying provided better quality and physicochemical characteristics.