Effects of UV-C irradiation on the physicochemical properties of freeze-dried beetroot (Beta vulgaris) powder†

Abstract

UV-C irradiation, known for its germicidal properties, is an effective postharvest food preservation method that enhances bioactive compounds in fresh produce. However, many of these bioactive components are susceptible to thermal degradation, meaning that conventional thermal-based preservation methods may not retain the UV-C induced bioactivity. This study aimed to investigate the effect of UV-C irradiation (1.25 × 10⁻³ J cm⁻²) on freeze-dried beetroot to determine whether similar enhancements in bioactive components occur. Compared to the untreated sample, the UV-C treated beetroot powder demonstrated significantly higher loose bulk density, higher tapped bulk density, lower hygroscopicity (p < 0.05), improved flowability, and reduced compressibility. Additionally, the treated powder exhibited significantly lower ash content, and increased levels of total betalains (by 3.9%), total flavonoids (by 1.9%), and ascorbic acid (by 6.6%). These results suggest that UV-C treatment positively impacted several physical characteristics of the beetroot powder, particularly in terms of compactness, flowability, and moisture stability without affecting its solubility or solubility rate. UV-C can serve as an effective processing step to enhance certain bioactive compounds while influencing the mineral content and carbohydrate content of the beetroot freeze-dried powders, potentially offering increased health benefits.