Barley Grain Non-specific Lipid-Transfer Proteins (ns-LTPs) in Beer Production and Quality

Abstract

Plant non-specific lipid-transfer proteins (ns-LTPs) are known for their ability to transfer various lipids between membranes in vitro. These ubiquitous basic proteins, that all share alpha structure stabilized by four disulphide bridges, are characterized by the presence of a hydrophobic cavity able to accommodate lipid molecules. According to molecular mass, this multigene family is subdivided into two subfamilies, ns-LTP1 (9 kDa) and ns-LTP2 (7 kDa); both located in the aleurone layer of the cereal grain endosperm. Ns-LTP1 is a prominent protein in barley grain, malt and beer. Numerous studies performed on its structure and function confirm its important role in grain protection, as well as brewing technology. As the major beer protein crucial for many aspects of brewing, ns-LTP1 can affect beer production and quality. Comparatively, there is less data available on the less abundant ns-LTP2. In this review, the focus is on recent progress on the structure, biological and technological function of barley grain ns-LTP1 and ns-LTP2, with an emphasis on their importance in brewing.