Influence of different drying methods on the physicochemical properties of red beetroot (Beta vulgaris L. var. Cylindra)

- The kinetics for convection drying and for combined method were studied.
- Two different drying methods induced the main changes in red beetroot structure.
- The betalains content and total phenolic content were investigated.
- Spectrophotometric method was used to determine the betalains content.

There is an increased interest in preserving fruits and vegetables by drying. The novelty of this study consists in the combination of the following three drying methods: free convection (at 50, 60, and 70 °C), forced convection at 40 °C and 315W microwave power. The aim of this study was to investigate the effects of the drying conditions on red beetroot (Beta vulgaris L.) in terms of betalain variance, and polyphenol, microstructure changes (SEM). A strong thermal shock, provided by convection at 60° followed by microwave wattage 315W/9 min, leads to a better preservation of bioactive compounds content (0.631 ± 0.0042 mg/g of betacyanin and 0.795 ± 0.0019 mg/g betaxanthin) when compared to convection at 50, 60 and 70 °C. The results showed that combined drying methods led to a significant preservation of the phytochemical content as compared to the traditional methods.