Optimum Ripeness: Picking for perfection

Friday, 25 July, 2014
Elona Hesseling, WineLand
Although the impact of terroir and viticultural practices on the quality and style of a wine is widely recognised, the ultimate importance that picking date plays in ensuring that the desired style is attained, is frequently overlooked.

ELONA HESSELING investigates this multifaceted issue and how modern techniques can assist in determining the perfect picking time.

Talking to various winemakers and viticulturists following the 2014 harvest, it became clear that this was an “interesting” year, one that certainly kept everyone on their toes. In such a vintage, when producers cannot simply rely on prior experience, the value of science and modern techniques become increasingly important.

While ripeness is generally related to grape quality, determining optimum ripeness is a much more complicated matter. The term ‘ripe’ is also very vague and will primarily depend on the style of wine to be made, such as a lighter, unwooded Chardonnay which requires grapes with a different ripeness level than a fuller bodied, oaked Chardonnay.

A study by JJ Hunter et al on the Role of Harvesting Time/Optimal Ripeness in Zone/Terroir Expression, explains that “optimal ripeness cannot simply be described by the maximum accumulation of grape components, but rather represents a complex, particular combination of physiological/biochemical changes, physical changes and required grape/wine style and market preferences”.

Measuring ripeness

Although the traditional use of balling/brix and acid content as criteria for ripeness does provide some relevant information, it cannot be used in isolation. Degrees balling is a measurement of concentration and does not specify whether more sugar is accumulating, or whether the berry is just losing volume or shrinking.

A few years ago the use of phenolic ripeness as an evaluation tool became a much discussed topic. Andy Roediger did extensive research on using the Glories method for the analysis of phenolic ripeness.

Phenolic ripeness as measured by the modified Glories method quantifies the amount of anthocyanins that a grape can produce and, in a way, also the quality of the grapes. Andy explains that the measure of extractability of these anthocyanins is an important indication of ripeness – the higher the extractability, the riper the grapes will be. “In addition, the amount of tannins are measured relative to the overall phenolic compounds,” he says. “The concentration of these tannins are measured as seed tannins, as well as those derived from the skins; the relative ratio is of interest here, which will indicate tannin ripeness.”

“Winemakers are looking for tannin ripeness and as such, it is important to assess the type of tannins that are available,” Andy explains. “In certain instances it is noted that grapes may be phenolically ripe despite lower than expected balling measurements. I have found that winemakers sometimes allow the grapes to hang as long as possible to obtain maximum ‘ripeness’, which can often result in overripe wines. Phenolic ripeness is an additional tool to help producers decide when to harvest.”

A new indicator of optimum ripeness, notably used for measuring ripeness of white varieties, is berry colour. A study by Prof Alain Deloire, New method to determine optimal ripeness for white wine styles, shows that there is an interesting indirect relationship between berry colour and its aromatic potential. The technology used to measure berry skin colour, Dyostem, has been developed by Vivelys Society in France.

Dyostem has the potential to be very useful for profiling berry maturation, harvest potential and selection of the most appro­priate harvest dates. Although measurements can be taken with relative ease and in a short period of time, it is relatively expensive and requires a trained team to operate the system.

Another new and perhaps more practical way in which to predict the harvest date, particularly for red varieties, is berry sugar loading. This concept can be defined as the accumulation of sugar per berry, expressed as milligrams (mg) per berry, from véraison onwards. This accumulation gives an indication of the ripening process from a new perspective and is a particularly handy indicator for reaching a specific style.

Fairview winemaker Stephanie Wiid is busy with her Masters in this field and explains that this model concerns the stylistic development of different wine profiles/styles after sugar loading has stopped or slowed down (less than 3 mg per berry per day) and has reached a plateau.

A study by Deloire, Predicting harvest date using berry sugar accumulation, suggests that, depending on whether grapes are harvested in the early, mid or later stages of the plateau phase, the wine can be characterised by fresh fruit, neutral-spicy/pre-ripe or mature fruit flavours respectively. (See Figure 1.)

This plateau phase with varying flavour profiles may be reached at different sugar concentrations for different cultivars and environmental conditions. Once this plateau phase has begun, the evolution of ripening will furthermore depend on factors such as cultivar, water status, climate and viticultural practices used.

Thus, for each block, a tailor-made graph can be designed, noting the number of days after véraison that each flavour profile will theoretically be reached. This incorporates real data with scientific predictions to plan future harvest dates.

Influential factors

Etienne Terblanche, viticulturist at Delheim Wines, completed his Masters at Inra in France in 2012 on the influences of training system and grapevine water status on aroma precursors in Viognier.

He explains that while temperature is generally the most important factor, the impact of water availability is also vital. As a management tool, irrigation (amount, frequency and timing) provides an opportunity to influence wine style and improve quality, especially when it comes to aromatic cultivars. “Water in the plant has a major, multi-layered effect on the must, which will influence the end-product,” Etienne says.

A factor such as water availability not only influences the aroma concentration or quality, but to a certain extent also determines the possible style. Stephanie explains that with water stress, you will never reach the ‘fruit ripe/mature fruit’ style – “so, if you know you have water stress, it is better to pick at the ‘fresh fruit’ zone, while the berries have a higher volume, resulting in a better yield”.

The suitability of a cultivar to a specific site also affects the possible styles. While the aim is to pick for a particular style, it is important to consciously avoid picking in the middle, ‘neutral’ zone. This is where the importance of site selection comes in and Stephanie explains that if the site is optimal for a variety, there will be a greater potential to reach any of the desired styles. Some even believe that in top terroirs, there is no ‘neutral’ zone …

Viticultural techniques play an important role in reaching desired ripeness and these practices can be adapted to production objectives. However, it should be kept in mind that viticultural practices cannot be used as a stand-alone approach and should form part of the bigger picture.

Planning ahead

These modern techniques enable the producer to more accurately predict the picking date for a wine style, helping them make an informed decision in order to optimise the end-product.

“What you do before and during harvest determines about 95% of the end result; it sets the framework from where a particular wine can be made. The ripeness level dictates the style within specific boundaries, maintained by terroir and vintage,” Etienne says. “By tasting the wines and analysing our results after harvest we can plan for the next vintage, from pruning to picking date.”

Stephanie explains that while it is important to incorporate these modern techniques with personal experience, it affords a way in which to scientifically confirm predictions and confidently relay that to the viticulturists and producers. “It is optimising the way we work, helping us to prioritise grapes and prepare the cellar well in advance,” she says.

By approaching optimum ripeness on a scientific level and creating various building blocks, it also becomes possible to naturally manage the wine’s components without manipulation, from high alcohol to low acid levels.

Additionally, these techniques can be used to diagnose problems in the vineyard – by looking at the rate of sugar loading, vineyard problems such as water stress or vine health can be identified.

Combining forces

Stephanie emphasises that a new model shouldn’t just be followed blindly – “it is an additional tool which should be used in combination with other classical indicators, as well as experience and common sense,” she says. “These modern techniques and fancy technologies are often also very expensive and time consuming, and it remains a tug of war between the money spent and quality gained.”

Etienne explains that while tasting the grapes and spending time in the vineyard remains crucial, people are just not that well calibrated to recognise every nuance and that is where these tools can assist. “However, our subjectivity should also be embraced: it enables us to make wine with personality, instead of producing generic wines. The key is to integrate modern technology with traditional methods,” he says.

Deloire explains that the scientific aim is to better understand fruit growth and composition, and to develop tools and methods to predict or predetermine wine style in terms of aromatic characteristics. “Berry ripening, wine flavours, wine consistency and the elaboration of low-alcohol wines are among the priorities of the world-wide wine industry today,” he says. “Helping the wine industry to be sustainable and profitable should be a goal for all research and experimentation.”

There are many methods and tools to choose from, with a lot more underway in the future, and by understanding berry ripeness and picking grapes at the opportune time, it becomes possible to address these issues naturally.

Picking date seems to be the symbolic handover from the viticulturist to the winemaker, and collaboration and a common goal between these two parties is crucial. A combination of modern techniques and equipment, as well as experience and intuition lies at the heart of this decision, guiding the transition from vineyard to cellar.

While ripeness is generally related to quality, determining optimum ripeness is a much more complicated matter.

Fairview winemakers, Anthony de Jager and Stephanie Wiid, and Donald Mouton (Fairview viticulturist and farm manager), with the hand-sorted Grenache of the 2014 season meant for Fairview’s Caldera wine, a blend of Grenache, Shiraz and Mourvédre.

Figure 1: A proposed sequence of ripening for red cultivars.

Viticulture

Tags: picking, optimum ripeness, wine style, Fairview, Balling, Delheim