Induction of beta-lactoglobulin amyloid fibril formation by acid heating to reduce allergenicity and improve functional properties: Insights from structural changes and protein hydrolysis

This study investigated the effect of acid heating induction (pH 2.0, heating at 85 °C for 0–12 h) on the allergenicity and functional properties of beta-lactoglobulin (β-Lg) amyloid fibrils (Fβ-Lg). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the gradual hydrolysis of β-Lg with increasing acid heating time. Thioflavin T fluorescence intensity and transmission electron microscopy further illustrated the formation of amyloid fibrils. The findings from multispectroscopy and peptidomics revealed that the amyloid fibrils induced a more ordered secondary structure in β-Lg (Random coil decreased from 30.4 % to 28 % and β-sheets increased from 23.4 % to 29.5 %), a de-folding of the spatial conformation, and a modification in peptide composition over time. Notably, the allergenicity gradually decreased and the antioxidant activity gradually increased with the prolongation of treatment time. Among them, the IgE binding capacity of β-Lg heated by acid for 12 h was as low as 60.47 % and IgG binding capacity was as low as 80.27 %. This enhancement is attributed to the disruption of allergenic epitopes and the exposure of antioxidant peptides and functional groups, which are a consequence of amyloid fibrils treatment. Moreover, the IgE and IgG binding capacity of Fβ-Lg induced by acid heating for 10 h was not significantly different from that of 12 h, while the foaming characteristic was the best at 66.33 %. Overall, Fβ-Lg prepared by acid heat induction for 10 h demonstrated both hypoallergenicity and excellent functional properties. This finding offers novel insights into the preparation of hypoallergenic protein feedstocks.