Optimization of Anthocyanin Extraction from Banana Bract (Musa paradisiaca) and their Potential Application as a Natural Colorant in Cordial Beverages
Kurai Gareth Mawoneke *
Department of Food Processing Technology, School of Industrial Science and Technology, Harare Institute of Technology, Harare, Zimbabwe.
Violet Angel Dzinotyiwei
Department of Food Processing Technology, School of Industrial Science and Technology, Harare Institute of Technology, Harare, Zimbabwe.
Raphael Kwiri
Department of Food Processing Technology, School of Industrial Science and Technology, Harare Institute of Technology, Harare, Zimbabwe.
Felix Mujuru
Department of Food Processing Technology, School of Industrial Science and Technology, Harare Institute of Technology, Harare, Zimbabwe.
*Author to whom correspondence should be addressed.
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.
Keywords: Anthocyanins, box-Behnken design, natural colorant, thermal stability, musa paradisiaca bract, agricultural waste valorization