Here is the bottom line on this fairly well done study: Increasing your hang time will impact your color. However, there was no difference between 1 and 2 weeks after normal harvest dates.
Although the authors try to sell this as a study about wine quality, no sensory work was performed and they really only looked at color. Nevertheless, slightly riper grapes seemed to have a little better color stability after 18 months.
Reading this article after another recent gem on light and color highlights the possibility that looking at total phenols, or phenols in general is largely deficient in determining quality (an opinion I am developing). The grapes used here may have had more color later, but what about vegetal, peppery, or fruity flavors? Was there a difference at all in characteristics such as these? It seems to me most of us would take the diminished color at ripening stage 1 (about 22.5 Brix) and subsequent lower alcohol if we were confident the flavors were delectable and weren’t going to get any better. But do they get better? Or just stylistically different? If you want a summary of study details see below.
Perez-Magarino, S et. al: J. Agric. Food Chem. 2004, 52, 1181-1189
Tinto Fino (TF) and Cabernet Sauvignon (CS) were used to assess the effect of the degree of grape ripening primarily on wine color. Color changes during ageing of each treatment was also examined. The levels of flavanols, anthocyanins, and derivatives of both types of compounds, were assayed immediately after fermentation and at different times during aging in American oak barrels and in the bottle.
The ripening stages were approximately as follows:
1)conventional’ 22.5 Brix, pH 3.36, TA 7.76 (CS) ; 2) 1 week after (23.6 Brix); and 3) 2 weeks after (~24.2).
Fermentation between 25 and 28 °C with 40 mg/L SO2. The maceration time was ~ 14 days. Pressed at ~ <3 g/L sugar, transferred into barrels where malolactic fermentation and wood aging were carried out.
The results showed that “maturity date” or “ripening stages” effects were detected, but these are different for each individual component as well as for each of the two grape varieties studied.
In general, the dimer and trimer flavan-3-ol derivatives reached higher levels in the unaged wine made from the grapes collected on the later harvest dates which indicated that the degree of flavanol polymerization increased with the degree of grape ripening. However, this was only true in the CS. The TF had its peak in the middle ripening stage. There seemed to be only small differences between ripening stage 2 and 3, and certain compounds were even statistically higher in stage 2 than in stage 3. No difference in total phenols existed between stages 2) and 3).
WINE AGEING: “No clear trends with grape ripening were observed. In fact, the CS wines with the highest color intensity values were the wines made from the grapes collected on the 2nd harvest date.” The wines made from more mature grapes had higher levels of flavanols and their derivatives.
The free anthocyanin content decreased sharply during aging, the greatest losses taking place in the first months of aging. After 18 months of ageing, any initial differences in anthocyanins and its derivatives (termed ‘new pigments’) due to ripening stage were virtually erased. However, color intensity differences were maintained after 18 months and in all cases the percentage of blue increased as ‘new pigments’ increased (i.e. anthocyanin products that are not antho-tannin complexes). Wines made from ripening 2) 3) showed higher levels in these ‘new pigments’, in both TF and CS wines.
Summarizing: delaying harvest date between 1 and 2 weeks produced grapes with greater color intensity and a higher percentage of blue pigment. This increase in anthocyanin derivative levels contributes to color stability by maintaining color intensity and increasing the blue component.
Additionally, the results showed that the amount of time the grapes are left on the vines may need to be limited, because wines made from the grapes collected on the 3rd harvest date did not exhibit better color quality characteristics than the wines made from the grapes collected on the 2nd harvest date.