Proctase – a viable alternative to bentonite for protein stabilisation of white wines

White wines must be treated to remove proteins that could otherwise aggregate into light dispersing particles and cause unsightly haze. Bentonite is commonly used to remove the grape proteins responsible for haze formation, but is associated with significant processing and environmental costs. Proteases potentially represent an alternative to bentonite, but until now none has shown satisfactory activity under winemaking conditions. Proctase, a mixture of Aspergillopepsins I and II, is proposed as a viable bentonite alternative. It is food grade, well characterised and inexpensive, active at wine pH and at high temperatures (60–80°C). When added to clarified grape juice and combined with short-term heating (75°C for one minute), Proctase has shown excellent results in removing haze-causing proteins (80–90% total protein reduction). Experiments have been conducted at laboratory, pilot and commercial-scale across a range of juices. Sensory and chemical characteristics of wines made from Proctase- treated juice have not shown any significant differences when compared with bentonite-treated controls. In addition, the cost of Proctase treatment has been shown to compare favourably with traditional batch bentonite treatments.