Double interface formulation for improved α-tocopherol stabilisation in dehydration of emulsions

Encapsulation of hydrophobic nutrients can be achieved by freezing and freeze-drying of oil-in-water emulsions containing glass-forming materials. The addition of a polyelectrolyte layer on the protein-stabilised oil droplets may provide better protection to the oil phase against external stresses.

Soy protein-trehalose and whey protein-trehalose emulsions with (layer-by-layer, LBL) and without (single-layer, SL) ι-carrageenan were used as the delivery systems for olive oil with dissolved α-tocopherol. Emulsions containing 0.125 g kg(-1) protein, 0.42 g kg(-1) oil and 150 g kg(-1) trehalose with (LBL) or without (SL) 0.25 g kg(-1) ι-carrageenan at pH 3 were frozen and freeze-dried and their state transitions were studied. The stability of α-tocopherol in freeze-dried systems at 0 and 0.33 water activity (aw ) during storage at 55 °C was followed. Loss of α-tocopherol was found in soy protein-stabilised SL systems at 0.33 aw , and this loss coincided with trehalose crystallisation. The stability of α-tocopherol was retained in soy protein-stabilised LBL and whey protein-stabilised LBL and SL systems at all conditions. Trehalose crystallisation-induced loss of structure was confirmed from changes in emulsion properties and visual appearance.

Component sugar crystallisation contributed to the loss of sensitive compounds, but the stability of these compounds can be improved by the use of LBL formulations.