Comparing the effectiveness of different fining agents for protein stabilization of white wines

One of the most important parameters required by consumers for white wine is clarity. This parameter is influenced by the formation of haze that can occur due to various factors, mainly proteins. To remove the protein material from the wines, the most used product is bentonite. In the first part of the thesis, an in-depth literature review was conducted to explore the mechanism of protein haze formation in white wines, as well as the methods for achieving wine protein stabilization without compromising sensory attributes. Factors such as temperature and pH, which influence haze formation, are considered. The use of fining agents, especially bentonite, is common but necessitates careful application to prevent sensory alterations. Additionally, alternative techniques such as ultrafiltration and specific mannoproteins are discussed. In the second part of the thesis, an experiment was conducted to assess the effects that treating three white wines (Traminer, Manzoni Bianco, and Grüner Veltliner) with various fining agents has on wine protein stability and composition. The project included the examination and comparison of protein content, protein profile and heat stability iwerehe wines before and after treatment with each fining agent, as well as other compositional data as the content of organic acids. The Heat stability test was conducted to classify the wines as stable or unstable, and the results indicated that two out of three wines were heat unstable (except for Grüner Veltliner). The effectiveness of fining agents, including one type of bentonite, one type of dicarboxymethyl cellulose (DCMC), and two types of Functionalized Mesoporous Silicas (SMF-STD and SMF-SO3H), in reducing protein instability was evaluated. The results demonstrated that Bentonite was the most effective agent in stabilizing the wines, followed by SMF-STD and SMF-S03, while DCMC generally showed limited effectiveness. Furthermore, the impact of fining agents on total protein concentration and protein profiles was analyzed using RP-HPLC. Fining agents were found to decrease the overall protein concentration, particularly in TLPs. Bentonite consistently led to the most significant reduction in total proteins, followed by SMF-S03 and SMF-STD, while DCMC exhibited limited effectiveness. Overall, the use of different fining agents did not result in notable alterations in the organic acids levels of the Manzoni Bianco, Grüner Veltliner, and Traminer wines examined in this investigation. These findings contribute to the understanding of the performance of fining agents in improving the stability and protein composition of white wines, providing insights for the optimization of fining processes in winemaking potentially involving the use of fining materials that can represent and alternative to bentonite.