In-line dosing for bentonite fining of wine or juice: Contact time, clarification, product recovery and sensory effects

Abstract

Field tests to evaluate in-line dosing with bentonite followed by centrifugation as an alternative to batch fining for protein haze control in white wine or juice were undertaken. The tests were performed at a commercial winery with a Sultana wine and Gordo (Muscat of Alexandria) juice and using two types of bentonite: Vitiben and SIHA-Active-Bentonite G. Fining performance was monitored by heat testing and quantification of heat unstable protein by HPLC. Heat test turbidity and heat unstable protein concentration decreased to stable values between 30 s and 2 min after bentonite injection. Sensory evaluation of Sultana wine fined with Vitiben by balanced reference duo-trio difference tests detected no difference between untreated, in-line dosed, and batch fined wine. Furthermore the volume of wine or juice occluded in lees can be substantially reduced by centrifugal compaction. However, incomplete separation of bentonite from wine or juice during centrifugation produced a carryover of 30% of the added bentonite into the clarified wine. This carryover problem may be mitigated, inter alia, by reducing operating flowrate through the centrifuge or using multiple centrifugation steps (in parallel or series). Therefore, inline dosing followed by centrifugation provides a rapid processing method for protein haze reduction in wine or juice with a decreased volume of lees. It can reduce significant value losses presently arising in the wine industry from batch fining and the resulting quality downgrades that occur in wine recovered from bentonite lees by rotary drum vacuum filtration.Abbreviations ACN acetonitrile; AS Australian Standard; BSA bovine serum albumin; cyt. c cytochrome C; NTU nephelometric turbidity units; OLS ordinary least-squares; RDVF rotary drum vacuum filtration;Re Reynolds number; SSE sum of the square of the errors; TFA trifluoroacetic acid

New directions in stabilization, clarification and fining of white wines

“…Blade and Boulton (1988) showed that maximal absorption was reached rapidly, and was complete within 30 seconds of the addition. This is consistent with an earlier study (Lee, 1986), in which Gewürztraminer wine fined with bentonite was rendered stable 1 minute after bentonite addition and with later studies of in-line dosing described below (Muhlack et al, 2006;Nordestgaard et al, 2006). In comparison, bentonite fining in a winery setting typically takes one to two weeks, depending on the tank size and rate of bentonite addition used.…”

“…Results obtained from pilot-scale studies of in-line dosing by Colby and colleagues (Muhlack et al, 2006;Nordestgaard et al, 2006) confirmed that a contact time of only a few minutes was sufficient for adsorption of the hazeforming proteins by bentonite. There was no detectable sensory impact on the wine of in-line dosing compared to batch addition.…”

“…Protein adsorption during bentonite fining is rapid; the treatment effect is completed within several minutes (Blade and Boulton, 1988;Muhlack et al, 2006). Hence, the long processing time required for bentonite fining is constrained by gravity settling of the lees and to maximize wine recovery during racking.…”

Carrageenans as heat stabilisers of white wine

“…These hazes are commercially unacceptable and therefore the haze‐forming proteins must be removed before bottling. The current method of protein stabilisation in commercial white winemaking is by adding bentonite, a cheap, absorbent clay that is an efficient fining agent that binds grape proteins and removes them through sedimentation (Muhlack et al , ). The use of bentonite, however, has some negative aspects, such as loss of wine volume, incompatibility with filtration equipment and sustainable waste disposal challenges (Majewski et al ).…”

Protein haze in bottled white wines: How well do stability tests and bentonite fining trials predict haze formation during storage and transport?

“…The majority of these costs are associated with the quality downgrading of wine recovered from the bentonite lees. Winemakers should aim to use the optimum amount of bentonite for wine quality, cost and environmental reasons (Muhlack et al 2006). Optimum amounts of bentonite are determined by laboratory fining trials (Iland et al 2000).…”