The use of thaumatin and bovine serum albumin as proteins in model wine solutions in bentonite fining

Abstract

This study examined the viability of using thaumatin and bovine serum albumin (BSA) as proteins in model wine solutions for bentonite fining studies and compared them with unfined New Zealand sauvignon blanc (SB) wine. Bentonite fining trials were performed on model wine solutions and unfined SB wines (pH range 3.5 to 4.3). Thaumatin was more readily adsorbed onto bentonites of all types than BSA and its adsorption onto bentonite was less affected by the pH of the solution. Specifically, the amount of BSA adsorbed onto bentonite decreased significantly as the pH of the solution approached the isoelectric point (pI) of BSA while thaumatin was adsorbed at that pH due to its higher pI. Changing pH affected protein adsorption of real wine less noticeably than of BSA and thaumatin, and decreasing pH increased protein adsorption in contrast to the model solutions. Neither of the model solutions can fully represent the response of real wine to bentonite fining but they are simple and cost effective to prepare and reacted to changes in bentonite concentration similar to real wine. Thaumatin is potentially a better protein to use in simple model solutions for wine stabilisation studies like filtration where molecular weights are important consideration.