In winemaking, clarification and stabilisation processes are routinely performed post-fermentation to ‘finish’ wines; i.e., to remove constituents that increase the risk of undesirable physical or sensory changes occurring between bottling and consumption.1 Haze-forming proteins are removed via the addition of bentonite (a clay-based colloid that readily binds proteins) to achieve ‘protein stabilisation’, while ‘cold-stabilisation’ (i.e., chilling wine at < 0°C for ~2–3 weeks) precipitates potassium bitartrate, mitigating tartrate crystallisation post-bottling. Bentonite, and other processing aids and additives, are also used to remove constituents that adversely affect wine sensory properties, including: phenolic compounds responsible for astringency (harshness), bitterness, and browning; and volatile compounds that impart off odours and flavours, arising naturally or from spoilage or contamination/taint.1 However, ‘fining agents’ are seldom selective, so wine constituents that contribute desirable sensory attributes are often partially removed.1,2 Furthermore, the resulting ‘lees’ (precipitate) tends to retain ~2–3% of the wine being treated (but as much as 10% for protein stabilisation using bentonite3), resulting in significant wine volume losses.1,4 The combined loss of wine volume and quality from bentonite fining alone is estimated to cost the Australian wine industry ~$100M/year.4 Since conventional clarification and stabilisation methods are slow and energy intensive, and lees constitutes a waste stream that needs to be carefully managed, these processes also hinder the sector achieving key sustainability objectives. New methods that ‘finish’ wines rapidly, with higher recovery rates, and reduced waste and input costs are therefore needed.
The potential for novel winemaking applications of membrane filtration to drive profitability in the Australian wine sector as innovative alternatives to unsustainable winemaking processes will be showcased: from phenolic adjustment to taint remediation.