Microwave vacuum drying for crispy beet snacks: Process development, drying kinetics, and product qualities

Abstract

With the increase in snack consumption in the modern diet and health concerns over conventional products made by deep frying or baking, there is a need to develop novel processing methods to produce nutritious and better-for-you snack options from vegetables. The objective of this study was to develop a new microwave vacuum drying (MVD) process for crispy beet (Beta vulgaris) chips. Beet slices (Φ5 cm × 3 mm thickness) were dried under 8 kPa vacuum at microwave powers of 900, 1350, and 1800 W (corresponding to initial power densities of 3 W/g, 4.5 W/g, and 6 W/g). The drying times and drying rates were experimentally determined. Under the tested conditions, beet chips were dried from their initial moisture content of 0.80 kg water/kg wet mass to under 0.20 kg water/kg wet mass within 21–27 min. The average drying rates ranged from 0.167 to 0.312 kg water/kg dry mass/min with higher MVD power corresponding with larger drying rates. Puffing on the chip surface initiated between 10 and 15 min, corresponding to moisture content between 0.598 and 0.687 kg water/kg wet mass. The color metrics, water activity, texture properties, and total betalain content were measured across the drying time. Microstructure of the dried beet chips was evaluated using an imaging analysis approach. This study provides evidence that MVD is a promising method to produce crispy vegetable snacks.