The effects of total protein/total solid ratio and pH on the spray drying process and rehydration properties of soy powder

• A decrease in pH increases the particle size of the concentrate
• A decrease in pH decreases the viscosity of the concentrate
• A decrease in pH improves the dispersibility of the powder
• Total protein level in the concentrate affects the dispersibility of the powder
• The dextrose equivalent affects the energy cost and the water content of the powder

The effects of total protein/total solid ratio (TP/TS) and pH on the spray drying process and rehydration properties of soy powder were investigated. The results showed that a decrease in the pH of the feed from 7 to 4 resulted in an increase of particle size, wettability index (WI), dispersibility index (DI) and water content (WC) of soy powder. In contrast, the solubility index (SI) and viscosity decreased, presumably due to a decrease of surface charges near the isoelectric point of soy protein leading to the formation of insoluble complexes at pH 4. WC and DI of the powder obtained by spray drying decreased as TP in the powder increased, regardless of the dextrose equivalent (DE) of the maltodextrin (MD). The latest affects the DI and WC in the powder; with increasing DE, WC and the energy cost to manufacture the powder decreased, whereas DI slightly increased.

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