AF4-UHPLC: Two-dimensional separation of macromolecules in four white wines from South-Western France

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Proteins in wines contribute to “protein haze,” which, while not affecting health or taste, can detract from the visual appeal of wines to consumers. To mitigate this issue, winemakers commonly use fining agents such as bentonite, despite the high costs involved. To overcome these challenges, numerous studies employ various analytical methods to better understand the behaviour of proteins. A novel technique which separates compounds by size, Asymmetrical Flow-Field Flow Fractionation (AF4), allows for studying proteins without denaturing them. Given that most proteins share similar sizes, identification remains challenging. The aim of this work was initially to develop a new system enabling simultaneous analysis of the macromolecular profile of wines (proteins, mannoproteins) using AF4 and real-time protein nature analysis (hydrophobicity properties) using Ultra-High Performance Liquid Chromatography (UHPLC). By injecting two standards of different sizes and chemical nature, thaumatin protein and mannoproteins, the system was validated. The subsequent application of this system to Southwestern wines revealed distinct profiles across monovarietal white wines from four grape varieties. While the Colombard (COL) and Gros manseng (GM) varieties showed similar protein compositions with varying concentrations, the Len de l'el (LL) variety had only two types of protein and no protein was detected in the Mauzac (MZ) variety. Despite these variations, all varieties contained mannoproteins. This system shows promise for studying wine protein composition and could potentially find applications in other matrices.