Effects of different thermal treatments on physicochemical properties, gastrointestinal digestion, and in vitro allergenicity-related responses of an infant formula protein model

Different thermal histories can alter milk-protein organization, gastrointestinal digestion, and subsequent in vitro allergenicity-related responses. This study compared an unheated infant formula protein model (MM) with pasteurized (PM), ultra-pasteurized (UPM), ultra-high-temperature-treated (UHTM), and in-container-sterilized (ICSM) models using particle-size and zeta-potential measurements, electrophoresis, peptidomics, IgE-binding assays, and serum-sensitized KU812 cells. After simulated gastrointestinal digestion, PM, UPM, and UHTM digests showed smaller mean particle diameters than MM, whereas ICSM retained an MM-like particle size and exhibited the least negative zeta potential. Thermal history also altered protein association and degradation patterns during digestion and reshaped the relative abundance of eight putative allergen-related peptides, six of which were shared by all five groups. Numerically, PM showed the lowest relative IgE-binding reactivity (54% of MM), whereas UPM and UHTM retained higher values (93% and 90%), and ICSM showed an intermediate value (68%). UHTM digests produced the highest β-hexosaminidase, histamine, and IL-4 values, whereas ICSM showed the lowest β-hexosaminidase and histamine values. Overall, the effects of thermal processing were dependent on temperature-time history and biological endpoint rather than following a simple monotonic relationship with processing temperature. Peptidomic, IgE-binding, and sensitized-cell analyses therefore provided complementary information on the in vitro allergenicity-related properties of the digests.