Digestion of mixed protein gels using elderly static in vitro digestion model: Impact of microstructure on bioaccessibility of vitamins B12 and D3

The intake of food products that provide adequate amounts of nutrients is a strategy to deal with the changes in physiological functions that occur during aging that can lead to malnutrition. In this work heat-set mixed protein gels (MPG) composed of soy protein isolate (SPI) and whey protein isolate (WPI) are developed, with different SPI:WPI ratios (15 g protein isolate/100 g gel) and enriched with vitamins D₃ and B₁₂. Different protein ratios formed gels with different microstructures and rheological properties. The gel containing 70 % of WPI had a more homogeneous microstructure. The influence of the MPG microstructure on the digestion and bioaccessibility of proteins and vitamins using elderly static in vitro digestion was evaluated. An important result is that mixing SPI and WPI increased the proteolysis. Regarding vitamins bioaccessibility, vitamin D₃ became more bioaccessible after the intestinal phase, and there was no difference in vitamin B₁₂ concentration in the intestinal and gastric phases. Therefore, mixing SPI and WPI to produce MPG resulted in improved digestion of proteins, as well as higher bioaccessibility of the vitamins. The results indicated the MPG are promising protein matrices to be used in food products for the elderly.