Preparation of alginate microspheres by emulsification/internal gelation to encapsulate cocoa polyphenols

• The influence of different calcium sources and emulsifiers are evaluated.
• PGPR and calcium citrate produces a more stable emulsion.
• PGPR and calcium citrate produce microspheres less polydisperse.
• Increasing the disperse phase will increases polyphenols retention in microspheres.
• The fit to Peppas–Sahlin model suggests a mechanism of relaxation/dissolution.

Encapsulation of cocoa extract was performed by emulsification/internal gelation in alginate microspheres. A suitable gelling was determined with a minimum of 1.8 × 10−4 mol of Ca+2/g alginate. The pH influence in alginate gels showed similar viscoelastic properties in the range of pH 3.5–10. Citrate and carbonate salts were uses as calcium sources, obtaining smaller spheres with citrate source. Moreover, SEM of microbeads made with citrate show uniform surface while the carbonate ones seem rough. Emulsions were formulated with several concentrations of Span 80, Span 85, Span 80-Tween 80 and polyglycerol polyricinoleate (PGPR). The most stable, also with the smallest microspheres were that prepared with PGPR. A shrinkage gelation factor of 0.8 was observed between drop size of emulsions and blank microspheres obtained, maintaining the shape and size distribution. When cocoa extract was encapsulated in microspheres, around 60% of retention was easily reached. The Peppas–Sahlin model fitted polyphenols release from microbeads, suggesting the existence of a relaxation/dissolution mechanism. The obtained cocoa microbeads could increase the daily intake of antioxidants when implemented in a food product.

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