Steak, Wine and NDVI
Updated: Apr 5, 2020
Ask any braaimaster the secret to prepare a luscious prime steak. Two topics will come into play: Preparation and planning. Preparation to make sure the fire is going strong and the meat has been seasoned. The final and most vital step is the braai process of course; to make sure the meat is cooked according to your guest’s preferences be it rare, medium or well-done. I want to leave one question in your mind, before we move away from braaiing and get to the serious stuff. If you had three friends, each with a different meat preference (rare, medium and welldone) sharing one piece of steak, how would you prepare to braai the steak? Would you cut the steak in three pieces and give the needed attention to each or would you just go ahead with the braai and hope the heat is strategically spread under the steak...? Terroir Same in viticulture, preparation for harvest is done with canopy management to ensure the grapes are ripening in the ideal climate to deliver the quality aromas in wine. The final and most important factor affecting the grape composition before making the wine is harvest. At what balling are you harvesting? Where did you sample? Are you harvesting the whole block or only certain parts of the block? Is harvest time based on sensorial- or chemical analyses? Canopy management can be seen as the human contribution to Terroir. I think it is safe to say terroir and point of harvest is the two biggest factors affecting grape composition and wine quality. Terroir is derived from the French word terre meaning “land”, but not so simple. Terroir is a network of environmental factors (solar radiation, aspect, wind orientation, elevation and more) all working together in their own space to create a holistic team effort to contribute to the aroma composition in grapes and eventually wine. Terroir gives wine a proof of identification, a reasonable background check, to know where and why quality is achieved. For this segment I am going to break down the romance and refer to terroir as climate. Macro-climate refers to the production region (Stellenbosch), meso-climate refer to the terroir of the production block and micro-climate refer to the climate inside the canopy surrounding the grapes. Although most of the vines are sharing the same meso-climate throughout a block, there would most probably be vigour variations due to soil variation. The soil will differ in water holding capacity, texture and topsoil composition throughout the production block. Affecting nutrient transport and directly affecting the vigour of the vines. (more information about our EMI soil variation mapping services available at revolutesystems.com)
At Revolute Systems we use satellite technology like NDVI (normalized differenced vegetation index) to group vines with similar micro-climates based on their vigorousness. This allows us to identify vigour variation in a production block and shifts us one step closer to knowing what aroma compounds are derived from a specific vigour zone or aromatic zone, if you will.
Maybe a bit far fetched to implicate we can farm for flavours? All I am saying is; vigour affects the phenolic content in grapes and phenolic composition is what drives aroma in wine. Phenolics are basically the DNA of wine and contributes to flavour, mouthfeel and even colour. Maybe not too far fetched..if we can effectively investigate terroir variation.
This harvest season, we motivated our clients to zone up blocks according to different vigour zones (low-, medium- and high vigour) in order to sample and harvest more accurately. The results showed that low vigour grapes had a higher balling (0B) than high vigour grapes. Mostly because with vines with low vigour has lack of leaves and bunches are more exposed to the sun. In some cases, we found a difference of 2B by just sampling according to NDVI. The difference in sugar content was a tangible measurement of NDVI efficiency. But what really makes me wonder is, how can we manipulate the aromatic compounds in grapes like pyrazines, thiols and terpenes to give us either vegetative, tropical or citrus aromas in wine.
Canopy management and cultivar aroma
Vineyard actions like tipping, topping and leaf foliage can be used to the viticulturists advantage in order to manipulate grapes into different aromatic classes. These actions can be used in contrast to fight natural vigour or in collaboration to work with the natural vigour of the vine.
Sauvignon blanc Studies have shown that cool climate limits the breakdown of berry aromas and preserves pyrazines. Pyrazines are responsible for vegetative flavours like green pepper and herbaceous odours in wine. Pyrazines are active in the grapes from as early as fruit-set and stays present, if not broken down by a well aerated canopy. Typical aromas derived from cooler climate Sauvignon blanc are green, grassy, green figs and green pepper. In warmer climate the volatile thiols will dominate the pyrazines causing more tropical and fruitier aroma composition in the grape and wine. Typical aromas derived from warm climate Sauvignon blanc includes kiwi, pineapple and passion fruit.
Shiraz Shiraz in known as a warmer climate cultivar and loves the raw heat dancing on its grapes during ripening time. In warmer climate shiraz tends to deliver aromas like liquorice, cloves, dark chocolate, hints of vanilla and jammy fruit. In cooler climate shiraz tends to lean towards the ever-famous spicy roots of this rugged varietal. Mint, black pepper and eucalyptus aromas are derived from cooler climate Shiraz.
For every production block there is a hand full of manipulation actions to be done to achieve specific aroma compositions, depending on what the winemaker craves. At this day and age canopy management are done universally throughout a production area, be it tipping, topping or leaf foliage. Taking the practicality of execution into account with the lack of skilled labour in South Africa, I do understand the challenges of farming precise. But one must ask yourself, what if we overcome these challenges? Where viticulturists farm for flavour components and winemakers can start the blending process in the vineyard. I believe NDVI maps and vigour zones could be utilised to pin-point canopy management actions in production blocks. The old Afrikaans saying “om te meet, is om te weet” pretty much sums it up. To measure the vigour variation in a block allows us to understand what specific canopy manipulations could be done to obtain quality wine in the quest to farm for flavours. How would you like your steak?