Physicochemical and Bioactive Stability of a Beetroot–Tarragon Microgreen Beverage During Refrigerated Storage

Consumers are looking for plant-based drinks that provide natural colour and bioactive compounds. Microgreens can be used as a source of pigments and phenolics for such beverages. This study developed a beetroot–tarragon microgreen beverage using hydroalcoholic extracts obtained with a green extraction approach and examined its stability during refrigerated storage. The drink was evaluated for proximate composition, water activity, colour parameters (CIE L*a*b*), microbiological quality and antioxidant activity by the ABTS radical cation decolorization assay (ABTS) over 15 days at 4 ± 2 °C. The beverage showed low fat and energy content and water activity values close to 1.00, so microbiological safety relied on pasteurization and cold storage. Escherichia coli and Staphylococcus aureus were not detected, while total aerobic mesophilic counts reached 104–105 colony-forming units per gram (CFU/g), with slightly lower values in samples containing tarragon. Colour measurements indicated betalain loss and colour fading in the beetroot drink, whereas the reduction in E* was more than 80 percentage points lower in the beetroot–tarragon beverage than in the beetroot-only drink, indicating a strong protective effect of tarragon microgreens on colour stability. For the mixed beetroot–tarragon beverage, mean TEAC increased by about 37% between day 1 and day 10 of refrigerated storage. These results indicate that beetroot and tarragon microgreen extracts can be used to formulate refrigerated plant-based beverages with acceptable colour, microbiological safety and antioxidant capacity.