Freeze–thaw resistant egg tart bakery emulsion: Fat crystallization, freeze–thaw stability, oral tribology, and egg tarts texture characterization

This study blended palm oil (PO) and anhydrous milk fat (AMF) to develop a freeze–thaw stable egg tart bakery emulsion. We investigated the crystallization behavior of PO:AMF blends at different ratios and their effects on emulsion properties, freeze–thaw stability, and product texture. During freeze–thaw cycles, the blend oil exhibited polymorphic transitions: β′ crystals predominated under freezing conditions, while β crystals prevailed during thawing. Freeze–thaw cycles induced coalescence of oil droplets, increasing particle size and viscosity. The emulsions with PO:AMF ratios of 1:1 and 1:2 exhibited greater freeze–thaw stability than the pure oils and the commercial product. After FT5, the blend groups (1:1 and 1:2) exhibited little change in rheological properties, zeta potential, and particle size, and no phase separation or clumping. Notably, the blend groups also showed lower interfacial protein loss rates (<24% vs. >32% for neat oils) and a significant increase in interfacial protein proportion at FT5 compared to FT3. In contrast, the commercial product exhibited pronounced phase separation and clumping. The change in the stability of the blend group may be attributed to increased viscosity and to the crystallization of the blended oil at the interface during freeze–thaw cycles. Moreover, blend samples (1:1 and 1:2) maintained good baking quality after FT5, resulting in egg tarts with fine, pore-free, smooth cross-sections and good springiness. Overall, this study provides a feasible strategy for developing freeze–thaw stable egg tart emulsions and promotes the application of fat blends in frozen bakery products.

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