Optimization of Anthocyanin Extraction from Banana Bract (Musa paradisiaca) and their Potential Application as a Natural Colorant in Cordial Beverages

Abstract

Background: Banana bracts represent a potential source of natural pigments for beverage applications. Aims: To optimise anthocyanin extraction from Musa paradisiaca bracts and assess extract stability as a natural colourant in a cordial beverage. Study Design: An experimental optimisation and stability study using a Box-Behnken design, followed by extract characterisation and shelf-life assessment in a beverage matrix. Place and Duration of Study: Department of Food Processing Technology, Harare Institute of Technology, Harare, Zimbabwe, from September 2025 to May 2026. Banana bracts were collected from Mutasa District, Honde Valley, Mutare, Zimbabwe (approximately 18.7167 °S, 32.9667 °E). Methodology:  A Box-Behnken design was employed, varying temperature (40–70 °C), time (30–60 min), solvent-to-solid ratio (10–30 mL/g), and stirring speed (200–600 rpm). UV-Vis spectroscopy was used to characterise the pigment profile. UV-Vis spectroscopy characterised the pigment profile. Ammonium sulfate aqueous two-phase separation was used to evaluate anthocyanin enrichment. Thermal degradation kinetics were assessed between 60 and 90 °C. Extracts were incorporated into a cordial matrix, and colour stability was evaluated using Arrhenius extrapolation and polymeric colour measurements. Results: A linear model (R² = 0.54), adequate for factor screening despite moderate predictive power owing to inherent biological variability in bract tissues, identified solvent-to-solid ratio as the only significant factor (F = 24.73, p < 0.0001), yielding a verified TAC of 212.21 ± 8.20 mg C3G/100 g dry weight. Non-acylated cyanidin glycosides dominated the pigment profile. Aqueous two-phase separation caused only 7.4% monomeric anthocyanin loss and improved the enrichment index from 6.94% to 9.02%. Thermal degradation followed first-order kinetics (60–90 °C), with an activation energy of 75.6 kJ/mol. In the cordial, the predicted shelf life (80% colour retention) was 42 days at 25 °C and 233 days at 4 °C. Polymeric colour reached 83.1% at 55 °C by day 28. Conclusion: Banana bract anthocyanins demonstrate adequate colour stability in an acidic, high-sugar beverage under refrigeration, supporting further development as a natural colourant.