White without pink
The AWRI helpdesk has received six reports of ‘pinking’ in white wines this year, with two requiring investigation. That’s a few more than normal and while there is no pattern to the occurrences and no way to predict them, here are some tips about both prevention and cure.
Pinking occurs when white wines made under highly reducing conditions develop a pink colouration on sudden exposure to air. In many ways its bark is worse than its bite. The aroma and flavour of the wine are usually unaffected, but the pink colour can suggest oxidation – and bring a predictable response.
Additions of ascorbic acid during bottling are thought to help protect against pinking, but care is needed. Ascorbic acid reacts rapidly with oxygen to produce dehydro-ascorbic acid, and then hydrogen peroxide, which can oxidise the wine in the absence of sufficient SO2. If ascorbic acid is added, it’s important to also maintain adequate levels of free SO2.
If winemakers are concerned about pinking, predictive tests are available to assess the likelihood that a wine will be affected.
Fining with PVPP can be used to remove pink colour or pinking precursors from wine. Laboratory trials should be performed to establish the correct addition rate of PVPP required to either remove the colour or reduce the pinking precursors to a level where the wine passes the pinking test.
It is also possible that the formation of the pink colour can be reversed by exposure to UV light, but it is suggested that this be trialled first by placing a couple of bottles considered ‘pink’ on a window sill in direct sunlight.
The AWRI help-desk is a service provided to levy payers though AGWA funding and is accessible during business hours and contactable on 08 8313 6600 or by email: firstname.lastname@example.org. For urgent afterhours queries, Con Simos, AWRI’s Group Manager for Industry Development and Support, is available on 0448 889 432.