Physical properties and release behaviour of caffeine multiple emulsions stabilised by binary or ternary biopolymer soluble complexes under acid, bile and yogurt storage conditions

• Multiple emulsions were made with binary and ternary biopolymer soluble complexes.
• Droplet size, rheology and caffeine release depended on complexes composition.
• Complexes with WPC produced emulsions with higher viscoelastic moduli.
• Faster caffeine release occurred with complexes made with whey peptides.

Whey protein (W) and/or whey peptides (P) and carboxymethylcellulose (C) soluble complexes were designed and used for stabilising water-in-oil-in-water multiple emulsions (ME's) loaded with caffeine in the inner aqueous phase. Interfacial layer composition of the ME's affected the initial droplet size, bulk viscoelastic properties, and caffeine release rates in yogurt and under acid and bile conditions. Oil droplet size of all the ME's did not vary significantly over 21 days of storage. The molecular weight of the protein fraction predominating in the protein:polysaccharide soluble complex was a key factor in determining the ME's properties. When W predominated in the soluble complexes, as opposed to P, initial droplet size was smaller, the viscoelastic properties higher, and the caffeine release slower in yogurt and under acid and bile conditions.

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