What to know about berry growth and maturity?
After fruit set, grape berry growth begins. This stage will end with the maturation of the berry and will give way to harvest.
The two successive growth periods for grape berry development
Berry development consists of two successive sigmoidal growth periods separated by a lag phase (Coombe and McCarthy, 2000).
- During the first growth period, from bloom to approximately 60 days later, the berry is formed, and the seed embryos are produced. Rapid cell division occurs through the first few weeks and by the end of this period the total number of cells and layers within the berry has been established. At the same time during this phase, there is an accumulation of some solutes that that reach their maximum around véraison. The major compounds are the acids: tartaric (accumulates during the initial stages of berry development) and malic (accumulates just prior to veraison). Also, some phenols start to be accumulated in that period: tannins (Kennedy et al., 2001) and hydroxycinnamic acids (Licker et al., 1999). Concerning aromatic compounds, methoxypyrazines achieve their maximum content at véraison (Allen and Lacey, 1999).
- The beginning of the second phase of berry growth or fruit ripening (véraison) is characterized by softening and coloring of the berry. The berry approximately doubles in size between the beginning of the second growth period and harvest due to the large increase of many compounds that occurs as a result of a total biochemical shift into fruit ripening mode. The main compounds increased are the sugars (glucose and fructose), secondarily to them the accumulation of secondary metabolites in the berries, which drive the wine’s quality, also starts in this stage.
Production of various compounds during grape berry growth
In red grape varieties anthocyanin production is probably the most prominent compound of importance, while in white varieties most of the aroma compounds, volatile and precursors, are produced during fruit ripening.
Moreover, many of the solutes accumulated in the first period of berry development are reduced on a per-berry basis (not simply diluted): malic acid and methoxypyrazine reduction vary considerably depending on environmental factors. Seed tannins decline due to oxidation while skin tannins have a small decline (or remain stable) increasing the extractability of the tannins of larger size and higher level of polymerization.
The reproductive cycle of grape berry
From a biological perspective, the growth and maturity of the berry means that the vine completes the reproductive cycle. It develops a viable seed and produces compounds to protect it while doing so; with compounds like organic acids, tannins and pyrazines that can provide an unpleasant experience to birds and mammals.
At the end of the first period of growth, the seed reaches viability and the capability of germination. Therefore, the goal during the second period is to make the berry as appealing as possible to birds and animals so that seed dispersal can occur.
Harvest occurs after the seeds are mature, during a period where compounds in the berries are changing over time.
Choosing the optimal harvest date is essential for winegrowers, as it defines the yield, composition and quality of the grapes, and for winemakers it marks the quality and style of the wine.
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