Although the final decision is always based on taste, there are however a few scientific processes that are running in the background, constantly feeding us necessary information to take into consideration to make the best informed decision on when to harvest the berries.
One of these is to identify each area in the vineyard that is different. We do this with NDVI (near infra-red imagery). These images display the vines growing potential (energy). In nature, vines under increasing restraint will always mature their grapes (the vines reproductive organs) earlier than vines under less restraint, as they need to have the pips in the berries ripened earlier to ensure their reproduction and survival. In the same way vines under less restraint will take slightly longer to mature their fruit as the primary plant is not under any real danger of surviving.
As an example: the demarcated Block shown below is Merlot with a total area of only 0.5 ha. It is planted to exactly the same clone with the same rootstocks, but one can clearly see two very distinctive areas, one on the left that is indicated by the colour, brown and on the right yellow. The “brown area” is slightly less vigorous and normally ripens between 1 and 3 days, to perfect complexity, before the “yellow area”. The style of the wines made from these areas will also vary quite significantly.
As such each little area throughout all the Z and Fusion vineyards will be identified and demarcated and separately tasted until it reaches full maturity and complexity. We will further ferment and barrel age each of these demarcated areas separately as they are all unique and give us very good options at blending time. In parallel with our berry tastings we also do conventional berry analysis, including measuring the sugar, acidity and pH of the grapes. The sugar will be converted into alcohol, and as such it is a very important indicator to monitor. The acidity and pH are linked to each other. As the acidity reduces towards harvest, the pH will start increasing. It is very important to harvest the berries at a low pH as this naturally influences the health of your juice and protects the wine against oxidation and microorganisms.
At the same time we will be measuring the phenolic maturation of the berries. Phenols (including tannins) are structures that are synthesized in young berries and green shoots to repel insects or predators with a very astringent taste. At veraison no more tannins are synthesized, in fact tannins start reducing and polymerizing in the berry skin and seeds to form softer, riper and finer tannins. The Glories method analyses the amount and the ripeness of these tannins and is a great indication of how mature ones tannins are in the berry. At the same time the method also analyses the amount and extractability of anthocyanin’s (another group of phenols responsible for the red /black pigment in grape skins). These tests supply very valuable information that will be taken into consideration, in parallel with berry tastings, when deciding on the perfect harvest date.
Lastly we employ a method referred to as Berry Sugar Loading (BSL) and Berry Aromatic Sequence (BAS), a method that was developed in France by world renowned French Processor Alain Deloir. We worked very closely with him on employing and calibrating the method in South Africa. BSL follows the development of the actual amount of sugar being transported into the berries on a daily basis. The curve typically follows a trend where initially sugar is loaded into the berry at a fast rate, later reaching a plateau (see graph below). It also give us a glimpse into vine functioning. From the BSL developmental cure BAS has been developed for different cultivars. The BAS follows the transition and development of the aromas from fresh fruit to spicy to mature fruit, giving us some very valuable information into how the aromas, at any time in the berry, will translate to aromas in the wine made from it.
AS previously stated, Complexity cannot be measured; it has to be experienced with all one’s senses; that said all the other indicators as discussed above and methods of identifying the smallest of significantly different areas in the vineyards provide us with a lot of background information to base our final decision on.
For now we are patiently awaiting that perfect moment!