Reducing wine movements during production
Clarification is a major reason for moving juice and wine between tanks at wineries – either racking off lees after a period of static settling or passing juice/wine through a centrifuge or filter. Each movement requires a destination tank for the clarified product and uses labour, water and cleaning chemicals, as well as creating wastewater that needs to be managed. Furthermore, significant quantities of juice/wine can be ‘tied up’ in lees and are commonly subject to significant quality downgrades when processed by rotary drum vacuum filtration (RDVF).
This project is investigating the possibility of ‘reverse racking’ as a new way to achieve clarification with fewer tank transfers. In this process the small quantity of lees in tanks is removed from underneath the clear juice or wine so that the bulk of the liquid may remain in the same tank. In an idealised configuration, the lees would be clarified concurrently back into the top of the same tank using an RDVF alternative that does not result in any quality degradation.
Studies of lees removal using scale-model tanks
Experiments were performed with a range of scale-model tank designs. Cylindroconical brewery-style tanks (55° sloped bottom cone) showed some promise but are not a realistic industry solution because of the investment in new tanks required. Winery-style tanks (5°bottom slope from back to the front of the tank) performed poorly due to severe channelling of wine through the lees. Baffles, moving suction feet, acoustic and other vibration equipment fitted to winery-style tanks did not address this. However, sweeping arms at the bottom of winery-style tanks prevented channelling and allowed removal of lees until the lees level dropped below the top surface of the sweeper. As an industry solution, a sweeping arm is again not desirable as while it is compatible with winery-shaped tanks, it is a major retrofit that would need to be made to every tank and would still not allow the removal of a considerable portion of the lees. Some means of achieving the effect of the sweeping arm with a non-permanent fixture/technique would be the ideal solution. Efforts to achieve this have so far been unsuccessful. This project will now be put on hold but may be revisited in the future. As part of the wrap-up of the project, a workshop on lees will be convened at the Australian Wine Industry Technical Conference at which videos and data from the project will be presented alongside presentations from wine companies on their experiences with a range of RDVF alternatives.