Dehydrated tofu whey as cryoprotectant in protein-stabilized oil-in-water emulsions

Abstract

The cryoprotective effect of dehydrated tofu whey (DTW) and sucrose on freeze-thaw stability of sunflower oil-in-water emulsions stabilized by soy protein isolate was comparatively evaluated at equivalent carbohydrate content (0.066, 0.33 and 1.5 g/100 g emulsion). The influence of frozen storage time at -18 +/- 2 °C for different periods (1-130 days) was evaluated. Emulsion stability was assessed by oiling off and particle size measurements. For unfrozen and freeze-thawed emulsions, flocculation index (FI) was determined from De Brouckere mean diameters (D4,3) in the absence and presence of sodium dodecyl sulfate (SDS). Coalescence index (CI) was evaluated through variation of D4,3 values before and after freeze-thawing. Control emulsion, without cryoprotectant, was highly unstable whatever the frozen storage period. Both cryoprotectants improved emulsion stability by decreasing the amount of freezable water. However, the protective effect of DTW was better than that of sucrose. After a prolonged storage (130 days), a high stability to coalescence (CI < 2) was observed when DTW was added at the highest concentration. In contrast, sucrose only was effective as cryoprotectant at relatively short periods of frozen storage (< 30 days). The presence of other components of DTW as glycosylated whey soy proteins would give an additional protective effect. This study has demonstrated that the addition of DTW is helpful to improve the stability of protein-stabilized o/w emulsions subjected to freeze-thawing.