The use of W/O/W controlled-release coagulants to improve the quality of bittern-solidified tofu

Bittern is one type of traditional coagulant used for tofu production, but it often causes rapid solidification, resulting in poor quality tofu. To address this issue, water-in-oil-in-water (W/O/W) emulsion coagulants containing a bittern solution as the internal aqueous phase were prepared using a two-step procedure. The mass ratio (ωw/o, w/w) of the internal bittern solution to the oil phase in the water-in-oil (W/O) emulsion was 4:6, and polyglycerol polyricinoleate (PGPR) was used as a hydrophobic emulsifier at a concentration of 1.2 wt%. The mass ratio of the W/O emulsion to the external aqueous phase (ωw/o/w, w/w) was 6:4, and polyglycerol fatty acid ester (PGFE) was used as a hydrophilic emulsifier at a concentration of 0.8 wt%. To improve the stability and controlled release of W/O/W emulsions, bovine serum album (BSA) or whey protein isolate (WPI) was added to the internal bittern solution. Tofu prepared using the W/O/W emulsion coagulants during solidification were evaluated with respect to release time, water content, yield, color, texture, and microstructure. The results indicated that the W/O/W emulsion coagulants not only exhibited satisfactory controlled release, which significantly improved the tofuʹs water content and yield and made the tofu gel more homogenous and compact compared with the control, but also showed better dispersibility than W/O emulsion coagulants.