Encapsulation of tomato oleoresin using soy protein isolate-gum aracia conjugates as emulsifier and coating materials

Abstract

Dry-heated Maillard reaction was applied in the preparation of protein-polysaccharide conjugates. Reaction mixtures containing soy protein isolate (SPI) and gum acacia (GA) were dry-heated at 60 °C and 79% relative humidity for 3, 6 and 9 days. An increase in degree of graft, a* (red) and b* (yellow) parameters was found with increasing reaction time. Structural feature analyses suggested that attachment of polysaccharides to SPI led to changes in spatial structure and unfolding of protein molecules. The conjugates of 6 days showed significantly higher levels of emulsifying properties. Emulsion prepared with SPI-GA conjugates had smaller values of d32 and higher apparent viscosity than those prepared with mixture of SPI and GA. Toxicity assay showed that conjugates exhibited better biocompatibility compared with traditional emulsifier. Furthermore, the conjugates were used as coating material to encapsulate the tomato oleoresin by spray-drying. Moisture content and microencapsulation efficiency of powder increased with an increase in conjugates concentration. The results of controlled release showed that conjugates particles could protect most of the lycopene from being released in the stomach. The lycopene in particles presented an improvement of stability against light, humidity and temperature.