Protein "memory effect" induced by a heat transfer-directed precooling strategy enhances milk cream foam stability

Regulating the coalescence behavior of fat globules is essential for enhancing foam stability in aerated dairy systems. In this study, two precooling strategies with significantly different heat transfer efficiencies-rapid freezing in an ice-water bath (RF) and slow freezing in a refrigerator (SF)-were applied to raw milk-oil mixtures to examine their effects on protein structure, interfacial properties, and macroscopic foam characteristics. The results revealed that RF treatment, characterized by intense heat transfer, induced irreversible structural changes in proteins, increasing α-helix content and promoting hydrophobic aggregation. These alterations substantially modified interfacial properties: both the amount of adsorbed protein at the interface and the thickness of the interfacial membrane decreased (from 4.0 nm to 1.0 nm). As a result, RF treatment facilitated controllable partial coalescence of fat globules, leading to a stable foam system with fine bubble size, high firmness, and excellent shape retention. The RF-45 condition was identified as optimal. This study demonstrates that precooling based on heat transfer efficiency can impart a structural "memory effect" on proteins, offering an efficient physical strategy for the targeted regulation of fat globule coalescence and customization of foam properties.