β-Lactoglobulin (beta-lactoglobulin, BLG, Bos d 5) is the major whey protein of cow and sheep's milk (~3 g/L), and is also present in many other mammalian species; a notable exception being humans.

[11] β-lactoglobulin is of direct interest to the food industry since its properties can variously be advantageous or disadvantageous in dairy products and processing.

Such experiments show an unusual but important intermediate composed purely of alpha helices, despite the fact that the native structure is beta sheet.

[18] As milk is a known allergen,[5] manufacturers in European Union need to prove the presence or absence of β-lactoglobulin to ensure their labelling satisfies the requirements of the EC Directive.

[20][21][22] Laboratory polymerization of β-lactoglobulin by microbial transglutaminase reduces its allergenicity in children and adults with an IgE-mediated cow’s milk allergy.

[6] In September 2023, the European Innovation Council funded a Hydrocow project by Solar Foods, which aims to produce BLG with the help of Xanthobacter hydrogen-oxidizing bacteria, carbon dioxide and electricity.