Stability and oral tribological properties of base milk emulsions for tea-infusion applications: The impact of fat crystallization characteristics

Fat crystallization and sensory-flavor compatibility are critical determinants of the quality of base milk emulsions. Seven lipid systems with distinct crystallization characteristics were selected, including hydrogenated palm kernel oil (HPKO), palm kernel stearin (PKST), chemically interesterified oil (CIE), coconut oil (CNO), corn oil (CO), and two anhydrous milk fat (AMF)-containing blends, namely PKST: AMF (1:1, w/w) and CNO: AMF (1:1, w/w). These systems were used to investigate emulsion stability, viscoelasticity, oral tribological, and tea-infusion performance. HPKO, PKST, and CIE formed dense β′ crystal networks, exhibiting storage modulus ( G′ ) values of 10–100 Pa, nearly nine times higher than those of CO and CNO. These networks significantly enhanced emulsion stability, reducing the Turbiscan Stability Index (TSI) to below 2 and maintaining structural integrity throughout 20 days of storage. CLSM showed more uniform droplet distributions and fewer signs of coalescence in emulsions with dense crystal networks, indicating improved microstructural stability. AMF incorporation further refined crystal morphology and optimized the balance between emulsion stability and oral smoothness. In tea-infused milk emulsions, black tea-based systems exhibited superior centrifugal stability, with emulsion stability index (ESI) values reaching 95%, and better milk–tea aroma compatibility. In contrast, green tea infusion reduced stability and weakened the characteristic aroma perception of tea. Overall, the results demonstrate that fat crystallization characteristics govern the balance between emulsion stability and oral smoothness, while tea infusion type further influences the application performance of milk emulsions. These findings provide practical guidance for rational lipid formulation design and the development of tea-infused milk emulsions.