It is often useful to initially quantify the degree of haze in a hazy wine by measuring its turbidity. The turbidity value may be used to establish the severity of the problem, and provides a datum against which any subsequent treatments applied to the wine may be judged, in order to evaluate their effectiveness. The change in turbidity of a hazy wine following aeration is also a useful test for the characterisation of certain metallic hazes, including copper and iron instability.
Deposits in wine may be isolated by first allowing to settle undisturbed on the laboratory bench, carefully decanting or siphoning off the clear wine, and then centrifuging the remaining wine and sediment, as described below.
- Click here to see a video demonstration of isolation of deposit
- Click here to see a video demonstration of centrifugation of deposit
Small centrifuge tubes with a conical base in which the solid material may be collected may be used for readily apparent hazes; these will generally require centrifuging for 15-20 minutes at approximately 3000 rpm using a bench-top centrifuge. Very fine hazes may require a larger volume of wine to be centrifuged initially, and the solid material then transferred to the smaller, conical-based tubes and further isolated. Centrifuge tubes should always be carefully balanced before centrifuging. It is also very important that centrifuge tubes be thoroughly cleaned prior to use, to eliminate microbial or chemical contamination.
It may be more convenient in some cases to isolate wine deposits by filtration through a 0.45 or 0.8 µm membrane, whereby the solid material is retained on the membrane. This approach is only recommended for relatively large particles which are present in relative abundance, such as the larger crystalline deposits, as fine, amorphous material may become trapped within the pores of the membrane, or may be difficult to observe on the membrane surface if pale in colour.