Whey protein hydrolysate alleviates ovalbumin‐induced allergic responses in Brown Norway rats: associations with immunoglobulin E‐related responses and the gut microbiota–short‐chain fatty acid axis

Background Whey protein hydrolysate (WPH) has considerable potential as a functional food ingredient; however, its role in alleviating allergic responses and the underlying mechanisms remain insufficiently understood, particularly the potential role of gut microbiota and their metabolites. This study characterized the structural changes of WPH following enzymatic hydrolysis, evaluated its effects on allergic responses in an ovalbumin‐induced allergic rat model, and investigated the associated changes in gut microbiota and short‐chain fatty acids (SCFAs) to explore their potential involvement in the antiallergic effects of WPH. Results Whey protein hydrolysate was prepared by two‐step enzymatic hydrolysis. Compared with whey protein isolate (WPI), the amide I band shifted from 1651.85 to 1654.62 cm −1 , and the α ‐helix content decreased from 34.67% to 23.23%, with increases in β ‐sheet (10.69% to 15.66%), β ‐turn (11.03% to 12.63%), and random coil (43.61% to 48.40%), indicating a more flexible conformation. Whey protein hydrolysate inhibited hyaluronidase concentration‐dependently, reaching 70% inhibition at 60 g L −1 . In an ovalbumin (OVA)‐induced allergy model in Brown Norway (BN) rats, WPH was administered orally at 200, 500, and 1000 mg kg −1 day −1 for 42 days. Whey protein hydrolysate attenuated hypothermia and reduced serum immunoglobulin E (IgE), OVA‐specific IgE (sIgE), histamine, and β ‐hexosaminidase levels, while ameliorating jejunal damage and mast cell degranulation ( P < 0.05). WPH also increased the Richness, ACE, and Chao1 indices ( P < 0.05). Conclusion Whey protein hydrolysate alleviated allergic responses by attenuating systemic allergic responses, reducing mast‐cell activation and allergic mediator release, and partially restoring gut microbial richness and diversity, supporting its potential as a functional food ingredient.