Milk colloidal system as a reaction medium and carrier for the natural blue colorant obtained from the cross-linking between genipin and milk proteins

A promising natural blue colorant was obtained from the cross-linking between genipin and milk proteins. Milk was simultaneously used to extract genipin from the unripe genipap (Genipa americana L.) and evaluated as a reaction medium and carrier for the novel blue colorant. The effects of the milk composition (skimmed, semi-skimmed, and whole) on the kinetic of blue color formation in the colorant-loaded milk samples during their cold storage time for 96 h were evaluated using their color parameters and free-genipin content. The reaction between milk proteins and genipin were evaluated by FTIR spectroscopy. In addition, the blue colorant-loaded milk samples were characterized according to their droplet size distribution, microstructure, and phase separation kinetics. The milk fat content influenced the genipin recovery while the milk with higher protein content contributed to obtaining a more intense blue color. Using whole milk with 3.0 g/100 g fat content favored the light scattering and, thus, a blue colorant with a more intense ?b¹ and L¹ values was obtained. On the other hand, the use of skimmed milk with 0.5 g/100 g fat content resulted in more consumption of genipin due to its more protein content for the reaction of blue color compounds formation. Thus, a more intense and darker blue coloration was observed with lower light scattering. The milk composition did not modify the phase separation kinetics of the blue colorant-loaded milk. Therefore, our results have demonstrated that the milk was a suitable medium for the reaction of blue color formation and also a good blue compounds carrier.Industrial relevanceConsumer demands for natural colorants have increased in the last years.Thus, the new food industry challenge is to develop novel healthy, safe and high-quality food products based on natural colorants. Currently, the colorant market does not have still available a natural blue colorant. Therefore, the development of a novel natural blue colorant from plant material could meet this worldwide demand increasing the added value of many products such as ice cream, dairy beverages, and candies.