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| CSIRO | SOLVE | Issue 2 Feb 05 | |
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FOOD FUTURES
Judging the Wine in the Grape
By Brad Collis
Science is helping winemakers know when a vintage is on the nose. Much has been spoken, written and sung about the ancient art of the winemaker; that gifted individual who with a sniff, a gargle and a keen eye can deliver a sublime creation. However, while casual imbibers might sometimes eulogise these masters of the grape, Australian winemakers and viticulturists feel it’s time to add a little more scientific muscle to their craft. They say they need a more consistent supply of premium quality (A and B grade) fruit delivered to wineries if the Australian industry is to hold its international competitiveness and even increase its global presence. Australian wine exports were worth $2.745 billion in 2004. A consistently high-quality product at a competitive price is seen as crucial for the local industry’s growth. While all wineries specify the grape characteristics they want, delivering on this demand is another matter, and in the words of Southcorp Wines’ viticulturist Dr Richard Hamilton, it can be 'hit and miss'. 'We just don’t understand the way variables like environment, irrigation, canopy and nutrient management, and other vineyard factors really affect a vine’s performance', he says. 'We need to know at a physiological level how grapes respond to seasonal conditions and management decisions.' So the quest has begun to identify the relationships between all the influences on a vineyard’s performance, and the resultant wine flavours. Once this has been achieved, the next step will be to develop objective measurement tools with which a viticulturist will be able to respond more accurately to a winemaker’s specifications. This ‘grape and wine flavour’ project is part of CSIRO’s Food Futures Flagship*, involving a multidisciplinary team of scientists from its divisions of Plant Industry, Land and Water, Entomology and Food Science Australia, with research partners from the wine industry itself. The Food Futures Flagship, part of a wider CSIRO national research initiative, has been established with the specific intention of lifting the international competitiveness of Australia’s agrifoods sector by applying leading-edge technologies. So while the linking of grape berry development with the hundreds of compounds that eventually determine wine flavour and aroma is one ambitious task, it is paralleled by an equally adventurous project – the development of the world’s first bionic nose. This is where the entomologists come into the picture. There are insects – and microscopic nematodes too – that have vastly better sensitivity than the human nose, and work has already started on ways to harness this and create the winemaker’s ultimate tool – the ‘cybernose’. However, first things first. The CSIRO’s Dr Mark Thomas, who heads the grape and wine flavour project, says the initial objective is to understand grape berry development and the development of the complex factors behind wine flavours. 'We are looking to directly link the vine to the palate', he says. The project has begun by analysing vineyards which are similar but produce vastly different berries and wines. It is hoped that biochemical analysis of the berries and the winemaking practices will identify which chemical compounds in the fruit correlate with the sensory characteristics of the grapes and wine. Yalumba’s head winemaker, Louisa Rose, says the research’s potential for the industry is enormous: 'One of the issues with the wine industry, and perhaps the food industry generally, is that a lot of decisions are made subjectively – the judgment of an individual. 'It’s been happening, of course, for a long time, and there are some very skilled people, but when it comes to the crunch it is still a subjective decision.' Ms Rose says it is now time to try to get some technical back-up; to put some objective measures in place for people who have to make critical judgments. She says that one of the difficulties for winemakers is that sensory characteristics can’t be judged until many of the compounds that influence a wine’s flavour and aroma become volatile as alcohol becomes part of the mix. However, by this stage there is not much a winemaker can do to correct any serious shortcomings. She says that if these compounds could be detected much earlier, ideally at the start of the season, vineyard management could then be used to keep grapes to specification. 'The aim is to know at the start of the season, the quality of the grapes you are likely to get, and what the vineyard manager can do to bring them up – to get C, D or E grade grapes up to A grade by the time they are harvested.' Ms Rose says the research project is also notable for the way the whole industry has got behind it: “It’s been very exciting being in a room with a diverse cross-section of industry specialists who all have the goal of making Australian wine a more consistently higher-quality product. 'The Australian wine industry really works well together at the production level. Our vineyards tend to be very different, so we are never all going to be making the same wines. But we all can be making better wines.' Enter the Cyber Judge The human nose is a remarkable organ. Walk into a room and most people can instantly recognise and differentiate a wide range of smells, or odorants (chemical compounds). It is a sense that has kept humans and other animals alive and safe for millions of years, and as impressive as the human nose is – with 300 active receptor genes the average person can detect thousands of odours – it is no match for the rat (which has three times more receptors to do the job) and, significantly, the humble nematode.
This microscopic worm has 500 olfactory receptors – the proteins that cause a neurological reaction when they come into contact with the molecules of a particular chemical compound – and are a key target for CSIRO scientists who believe they can replicate this in new biosensor technology. Because the nematode’s genome has been sequenced, scientists are already able to identify the genes responsible for the receptor proteins and aim eventually to reproduce synthetic protein receptors. The head of the CSIRO Food Futures Flagship Cybernose Project, entomologist Dr Stephen Trowell, says two critical problems have to be solved before the cybernose can become a reliable wine judge. The first is the detection of specific molecules. The second is the development of an algorithm for pattern recognition, because at the molecular level the ideal wine flavour and aroma is a ratio, or pattern, of compounds. To achieve the first goal, the researchers will enlist the fruitfly (Drosophila melanogaster – not related to fruitflies such as the Queensland fruitfly that damage fruit) whose olfactory receptors are already attuned to fermenting fruit and the flavours of winemaking. Because the fruitfly’s genome has also been mapped, it is possible to isolate the genes responsible for its receptor proteins and transfer them into the nematodes. It will be the mapping, using digital photography, of the nematodes’ quantitative response (illustrated by movement patterns) to the different compounds associated with wine flavours that will identify which of the many receptors in the fly are suited to the task of measuring wine aromas. Insects, such as bees, are known to learn and discriminate complex odours, and study of their brains will eventually give scientists the algorithms, or mathematical basis, for their cybernose – a machine that can analyse and compute its detection of flavour compounds. The timeframe for the research is seven years and Dr Trowell is confident his team will have a working model by then. Aside from the obviously complex science required to harness biological processes from insects and turn them into a machine, he says that machine also needs to be practical: 'It will need to be portable, have considerable computer processing capacity, and not be expensive', he says. There’s also the considerable technical issue of ‘amplification’ – getting a measurable signal from an infinitesimal reaction as the protein molecules react to a few molecules of a compound. The commercial stakes in solving this are considerable because it would open up a whole new role for biosensors in areas such as medicine, food storage and security. Not surprisingly, Dr Trowell, is a bit guarded on this point, but admits his team 'has a few ideas'.
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But
there is increasing competition, internationally and also in the domestic
market, from Spain, Italy, South Africa, the US and Chile.
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