Influence of must fining on oxygen consumption rate, oxidation susceptibility and electrochemical characteristics of different white grape musts

Abstract

AIM: Pre-fermentative fining is one of the central steps of white wine production. Mainly aiming at reducing the levels of suspended solids, juice fining can also assist in reducing the content of oxidizable phenolics and therefore the susceptibility of juice to oxidation. There is a large variety of fining agents available on the market, many of which have been introduced in recent years in response to specific dietary requirements. The aim of this work is to characterize different fining agents for their ability to reduce oxidation susceptibility of must of different white grape varieties.

METHODS: Musts of Pinot grigio, Garganega and Chardonnay were produced in the laboratory and submitted to different fining treatments by means of casein, PVPP, potato protein, pea protein, or combinations of potato protein and PVPP. All fining also included pectolitic enzymes. Following cold settling, clear juice was racked and submitted to chemical and electrochemical (linear sweep voltammetry, LSV) analyses, as well as to cycles of controlled oxygen consumption to assess oxidative behaviors. A control treatment consisting of cold settling only with pectolitic enzymes was used as control.

RESULTS: Not all fining treatments were able to impact juice oxidative behavior. Common fining agents such as casein showed marginal impact on oxygen consumption rates, content of oxidizable phenolics and browning susceptibility. Conversely, pea protein, alone or in combination with PVPP, showed great capacity to reduce the content of oxidizable phenolics and the ability of the must to undergo oxidative reactions. LSV could be used to effectively monitor the removal of oxidizable phenolics during the treatment.

CONCLUSIONS: 

This work illustrates the importance of the type of fining agent in the context of managing must and wine oxidation susceptibility. It also highlights the potential of a simple electrochemical technique such as LSV to monitor the effectiveness of fining towards oxidizable phenolics. ACKNOWLEDGMENTS: The present work was financially supported by Biolaffort