Freeze-thaw stability and oil crystallization behavior of phospholipids/whey protein-costabilized acidic emulsions with four oil types

The physical properties and freeze-thaw behavior of mayonnaise-like emulsions prepared from 60% (v/v) olive oil (OLO), peanut oil (PNO), palm oil (PO), and coconut oil (CNO) at pH 3.0 using whey protein isolate (WPI) as the stabilizer and soybean lecithin (SL) or egg lecithin (EL) as supplementary surfactants were investigated. For all oil types, the addition of SL or EL decreased emulsion stability due to partial displacement of WPI at the interface. Nevertheless, both surfactants generally improved the emulsion freeze-thaw stability except for OLO emulsion. The thermometry of fat crystal formation in PNO (Tfat = 0.4 °C), PO (Tfat = 6.6 °C) and CNO (Tfat = −1.4 °C) emulsions was higher than that of ice crystal (Tice = −10 °C) formation. On the other hand, ice crystallization occurred prior to fat crystal formation (Tfat = −14 °C) in OLO emulsions. Upon freezing, serum phase ice crystals protruded into OLO emulsion droplets with a mixed SL-protein thin membrane leading to a reduced stability than WPI-alone emulsion. Compared with SL, EL was more capable of facilitating fine fat crystal formation, and partial fat crystallization generally increased emulsion viscosity. Overall, both small surfactants promoted crystallization behavior and freeze-thaw stability of WPI-based PNO, PO, and CNO emulsions; although slightly less effective than EL, SL showed a strong efficacy in the emulsion system.