Visual as well as spectrophotometrically measured colour changes were studied in six blanc de noir wines during ageing at 0, 10, 20°C and 30°C. Visual colour descriptions were compared with spectrophotometric measurements of absorbance at 420 nm and 520 nm, in order to obtain colour preference limits for this type of wine. A limit where the spectrophotometrically measured absorbance values at 420 nm and 520 nm do not exceed 0,200 and 0,160 respectively, was found best suited for this purpose. The results showed that the colour of blanc de noir wine is susceptible to change during ageing. This deterioration of colour quality during ageing occurred especially in wines which initially had a more intense colour. High temperatures during ageing have a detrimental effect on the retention of colour quality.

Three grape maturity indices viz. degrees Balling (OB), OB total titratable acid (TT A) ratio and the OB.pH product of musts were compared regarding their ability to predict optimum quality for Cabernet Sauvignon and Pinotage wines. Comprehensive analytical data from 128 musts and corresponding wines for the 1979 and 1980 vintages from the Stellenbosch, Durbanville, Lutzville and Robertson areas were subjected to principal component analysis using variables and variable ratios selected by correlation to quality weighting. The results indicated that 0B alone could not perform the function of a grape maturity index for predicting optimum quality. In the case of the OB/TT A index, the range wherein maximum wine quality occurred was too wide to be of practical value in this instance. The 0B.pH index gave a narrower optimum range, and in contrast to the two other indices gave similar results for both cultivars.

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