Comparison of Methods for Estimating Protein Stability in White Wines

Abstract

Several protein stability tests have been proposed, but as their results are not always consistent, wine-makers may hesitate when determining a bentonite dose. The chemical composition of the naturally occurring protein precipitate of a Sauvignon blanc wine was compared with the precipitates obtained after using different protein stability tests. Chemical composition, molecular exclusion profiles, and electrophoresis profiles of stability test precipitates were compared with naturally occurring precipitate. All forced precipitates presented different chemical compositions than the naturally occurring precipitate. None of the tests is a perfect reproduction of the natural phenomenon. The slow heat test does not precipitate thaumatin-like proteins and the ethanol test precipitates a large quantity of polysaccharide, making neither test suitable. Results indicate the fast heat test is most similar to the natural precipitate in terms of its chemical composition and therefore is likely the most appropriate stability test. The results offer a thorough comparison of the chemical composition of a natural protein precipitate and precipitates obtained after applying different stability tests.