Soy protein-fortified beverages usually are formulated with traditional isolated soy protein varying in functionality and sensory attributes. Recently, a new transparent acid-soluble isolated soy protein (TASISP) has been developed through alternative processing methods. Traditional soy proteins typically are spray dried at a pH above the isoelectric point. As a result, these proteins create an opaque appearance when incorporated into a beverage. The new TASISP is spray dried at a pH below the isoelectric point. This TASISP has high solubility in the acidic pH range below 4.0.
Proper formulation and processing of low pH ready-to-drink (RTD) and powdered soy beverages are keys to ensuring stability and consumer appeal. Key processing advantages exist with TASISP compared to traditional soy protein in beverages with a final pH below the isoelectric point. Isoelectric point is defined as the pH at which the total charge on the protein molecule is equivalent to zero, resulting in the neutralization of available amino and carboxyl groups, according to S.A. Iqbal and Y. Mido, the authors of the 2005 book “Food Chemistry.” At this pH, the protein is not soluble, and as a result the protein precipitates out of solution.