Soy protein fortification affects sensory, chemical, and microbiological properties of dairy yogurts

Chemical, microbiological, and sensory properties for low fat yogurts fortified with 0, 1, 2.5, or 5% soy protein concentrate were determined through 1 mo storage at 5 degreesC. Yogurts were adjusted to equivalent total solids with nonfat dried milk. Microbiological counts, fermentation time, and final develop ed acidity were not affected by soy protein. Instrumental viscosity and sensory thickness, soy aroma, and soy flavor Increased with soy protein addition (P less than or equal to 0.05). Soy flavor and aroma did not increase with storage time. Yogurt with 5% soy protein was darker, more chalky, and less sweet compared to control yogurt or yogurts with lower concentrations of soy protein (P less than or equal to 0.05). Yogurts with 1 or 2.5% soy protein were most similar to control yogurt.