Development of cryo-desiccated whey and soy protein conglomerates; effect of maltodextrin on their functionality and digestibility

This study aims at enhancing the thermal stability, functional properties, and digestibility of the protein isolates by addition of maltodextrin. Higher total soluble solid content, less cohesiveness, and high hygroscopicity of maltodextrin allow the protein isolates to show better thermal and functional stability along with improved digestibility. The functionality of powders depends on their particle size, the structure of particles, shape, flowability, and wettability, etc. The effect of maltodextrin (5%, 10%, 15%, and 20%) on the functional properties of WPI, SPI, and the mixture of these proteins (1:1 ratio) was evaluated in this study. The samples were prepared in distilled water (10 w/v % solution of SPI and WPI), cryo-desiccated (freeze-dried), and then further dried using a fluidized bed drier (at 80, 90, 100 degrees C) to improve the functional properties. The addition of 15% maltodextrin was obtained as an optimum condition as it provides good functional properties (flowability such as cohesiveness, compressibility index, angle of repose, wettability, solubility, color, and water activity) with maximum thermal stability (113 +/- 2 degrees C for WPI, 115 +/- 0.5 degrees C for SPI and 118 +/- 0.1 degrees C for mixture) studied using differential scanning calorimetry. The powders were further characterized using FTIR, SEM, and SDS-PAGE to evaluate the effect of in-vitro digestibility on the protein conglomerates. The in vitro digestibility of the conglomerates containing WPI, SPI, and the mix was 91.24% +/- 2.5, 56.48% +/- 3.9, and 80.71% +/- 3.1, respectively, and show good stability in the gastric phase (pH < 3), which depicts the resistance of conglomerates due to maltodextrin. These protein conglomerates can be ingested orally to gain the benefits of plant and animal proteins simultaneously and can also be incorporated in functional beverages and food items to improve the nutritional value. Practical applications The functional properties of animal protein (WPI) and plant protein (SPI) were improved by the addition of maltodextrin. The maltodextrin improves the gastric digestibility and pH stability of the protein conglomerates. These animal and plantbased protein conglomerates can be utilized in diets or functional foods as a good source of protein constituents. Higher protein content with good solubility can be attractive to food manufacturers in preparing semi-solid and liquid novel food systems. Alternatively, these powders can be consumed as dietary supplement to increase the protein uptake and for better digestibility.