Impact of Protein Concentration and Salt Addition on the Rheological Behavior and Stability of Reduced-Fat Dressing-Like Emulsions Prepared With Tofu Whey

Tofu whey (TW) is generated as a by-product during tofu manufacturing. TW was processed to obtain concentrated tofu whey (CTW). The aim of this study was to explore the preparation of reduced-fat dressing-like oil-in-water emulsions with CTW, xanthan and guar gums (5.0 g kg⁻¹) and sunflower oil (250 g kg⁻¹) and evaluate the impact of protein concentration (2.5–10.0 g kg⁻¹) and salt addition (NaCl, 20.0 g kg⁻¹, in the aqueous phase). The emulsifying ability of CTW increased with salt addition, but the extent of this effect was smaller at higher protein concentration. At the lowest protein concentration (2.5 g kg⁻¹) and in the absence of salt, some creaming destabilization was observed, but in the presence of salt, a total stabilization was observed after 45 days of storage. At intermediate and high protein concentrations (5.0–10.0 g kg⁻¹), all emulsions were stable regardless of the salt addition. The stability would be ascribed to the formation of a three-dimensional network including gums, flocs, and CTW biopolymer aggregates. All systems behaved as pseudoplastic fluids in flow measurements and as weak gels in oscillatory assays. Although salt addition showed opposite results on rheological properties at low and high protein concentrations, stable emulsions were obtained. The biopolymers in CTW are suitable as emulsifiers in acid food emulsions such as dressings and sauces, with an appropriate response to salt addition. These findings contribute to increasing the added value of TW wastewater as a by-product of tofu manufacture in the development of stable emulsion-based food products.