Margarine-Like Emulsions Prepared with Coconut and Palm Oils: Analysis of Microstructure and Freeze–Thaw Stability by Differential Scanning Calorimetry

Abstract

The objective was to study the microstructure and freeze–thaw stability of margarine-like emulsions formulated with vegetable fats using differential scanning calorimetry. Emulsions were prepared with 20% w/w dispersed aqueous phase and a continuous lipid phase composed by coconut oil (CO) and/or palm oil (PO) plus polyglycerol polyricinoleate (PGPR) as emulsifier. Mean temperature (TM) and crystallization enthalpy (ΔHc) were obtained from the exothermic peaks corresponding to freezing of aqueous phase. Successive cooling–heating–cooling cycles were applied to analyze changes in the exothermic peak. The emulsion prepared with CO (without PO) and 1% w/w PGPR in lipid phase showed higher water droplets size (TM = −44.8 ± 0.1 °C) and lower quantity of stabilized aqueous phase (ΔHc = 28.9 ± 1.2 J g−1) prior to application of temperature cycles, while coalescence and (presumably) water transfer processes occurred during the treatment. The use of 2% w/w PGPR was sufficient to accomplish full stabilization of aqueous phase (TM = −45.9 ± 0.1 °C; ΔHc = 42.6 ± 0.3 J g−1) before and after the freeze–thaw treatment. The total or partial (50%) substitution of CO by PO in emulsions with 1% w/w PGPR also improved the stability of the system, exhibiting slight microstructural changes. This enhanced stability would be linked to reduced water droplets size because of more rapid crystallization of lipid phase and immobilization of aqueous phase after emulsion preparation. In conclusion, it is possible to obtain margarine-like emulsions prepared with CO and/or PO using relatively low emulsifier concentration and maintaining a desired microstructure after freeze-thawing if the percentage ratio of both fats is controlled.