- Modelling wine aroma and quality from its odorant content.
Our main line of research is the chemical characterization of wine aroma. Our objective is to be able to infer the sensory properties of wine from an analysis of the aromatic substances it contains and vice versa. All the time we are coming closer to achieving the comprehensive knowledge we are aiming for.
After years of research, we know which of the thousands of volatile compounds in wine are responsible for its aromatic notes.
We have specific methods of analysis for the main components of wine, all of them original and developed in our lab.
We are the only laboratory in the world where you can find this complete analytical service:
- Major compounds (30 fermentative compounds: alcohols, esters, fatty acids, diacetyl, methionol,…)
- Trace compounds (40 compounds of several origins: terpenes, ethylphenols, vinylphenols, guaiacols, whiskylactones, β-damascenone, β-ionone, cinnamates, vanillines…)
- Polyfunctional mercaptans or varietal thiol derivatives from cysteine and glutathione (4-methyl-4-mercaptopentanone, 3-mercaptohexanol, 3-mercaptohexyl acetate, furfurylthiol , benzylmercaptan, mercaptofuran)
- Very volatile sulphur compounds related with reduction problems (sulfhydric acid, dimethyl sulfide,…)
- Carbonyl compounds related with oxidative problems (methional, phenylacetaldehyde, E-2-nonenal,…)
- Polar compounds of different origin (furaneol, sotolon)
- Precursors and other compounds (glycosidic precursors, systemic and glutathionic precursors, amino acids and biogenic amines)
We also have procedures for screening the aromatic compounds of each wine and producing olfactive profiles. These procedures are essential for the diagnosis of any olfactive problem or for the definition of the aromatic profile of special wines. We are also able to apply reconstitution strategies from the perfume industry to verify the sensory role played by a component or group of components.
If you need to know the content of any of these components in your wines, if you have an aromatic problem or if you want to understand the aromatic keys of your wines, please contact us.
- Explanation of the chemical basis of wine taste sensory notes (bitterness, sourness, structure and astringency)
In wine tasting the first step is the description of color (visual phase), followed by aroma (olfactive phase) and finally by mouth tasting. It is in the mouth where the different tastes and sensations are perceived, while the aromas are also perceived in the retronasal pathway. Several studies by our group have proved that the sensory attributes perceived in the three phases are important in forming the concept of wine quality, and that they should all be balanced and consistent. The best aroma in the world is worthless if the mouth sensation is poor or unbalanced.
In the case of non-sweet wines (< 5 g/L of sugars), the perception in the mouth depends on the type of wine. Curiously, in the case of white wines the quality and intensity of the mouth perception -for an appropriate level of acidity- depends to a great extent on the wine aroma, and therefore on the compounds it contains.
In the case of red wines, although the aroma modulates the perception of some attributes, the intensity and quality of the mouth attributes depend primarily on the non-volatile composition. Organic acids are responsible for the perceived acidity while the different polyphenolic content, together with other non-polyphenolic compounds, determines the astringency of these wines. Another important attribute in the mouth is bitterness. The studies carried out by our group to identify the compounds related with this attribute have shown that although non-volatile compounds are involved in this taste, other attributes such as astringency and even aroma can modulate the perception of bitterness in wine.
- Evaluation of the aromatic potential and quality of grapes
The grape is essentially neutral in terms of its aromatic and gustative characteristics. Nevertheless, it is the key element in the future wine aroma, acting on it in three fundamental ways:
- Conditioning the yeast metabolism. The grape provides the essential nutrients (amino acids, lipids, vitamins and oligo elements) for the yeast to build its cellular structures. As all grapes have different profiles of essential nutrients but their cellular structures are basically the same, each yeast works in a unique way in each must. As a consequence, the fermentative aromas will have a composition highly dependent on the nutrients profile provided by the grape. Some elements of that profile are so dependent on the grape variety that the “varietal” profile of those wines is actually constituted by aromas produced by the yeast induced (or programmed) by the grape.
- Providing cysteinic precursors. Precursors from the family of aromas known as polyfuctional mercaptans, varietal thiolic aromas, or mercaptans are bonded to cysteine. These potent odorants have very characteristic aromas of boxtree, lemon peel or passion fruit. They are important in white wines like Verdejo or Sauvignon blanc, and also in many rosés. The grape accumulates these aromas, bonding them to cysteine ammoniated or integrated with antioxidant glutathione. Sometimes this bond is formed during grape disaggregation. These precursors can only be broken by the yeast.
- Providing glycosidic precursors. Almost all grape aromas are bonded to sugar molecules as odorless forms. A small amount of these “bonded” aromas is released during fermentation, giving varietal aromas, while another important part goes relatively unaltered to the young wine. This part will be slowly released during ageing, giving the elegant nuances associated to the “bouquet” of wines elaborated with excellent grapes.
At LAAE, we can determine the amino acids and precursors (glycosidic and cysteinic) of grapes. The results of these analyses may be crucial in viticulture and enology for identifying the cultural and climatological conditions that favor their formation, taking decisions regarding the kind of yeast, bacteria or nutrient most suited to favoring the release or extraction of the required aromas, and also to predict the type of aromas that will appear years later.
If you are interested in any of these issues, please contact us.
- Optimization of the grape-yeast-fermentation process
The most important aromatic compounds produced during alcoholic fermentation (major alcohols and their esters and volatile acids) are directly related with the metabolism of amino acids and fatty acids. The effect of must nitrogen on the generation of volatile compounds from the yeast metabolism is a complex one. It depends on the chemical form and concentration of nitrogen and also on the family of volatile compounds. This means that there is an interaction between the nutritive elements in the must and the metabolites generated by the yeast. Knowing the nutrients that the yeast requires, it is possible to prepare special nutritive supplements suited to each type of yeast. Therefore, it is possible to influence the aromatic expression of the yeast and to maintain every year the aromatic characteristics of the different wines.
- Modelling/optimizing wine ageing
Wine suffers a series of chemical transformations between the end of the fermentation process and the time of consumption. These affect wine stabilization and the maturation of its organoleptic properties.
An important part of these processes takes place inside a closed bottle so that there is no possibility of intervention or correction. Furthermore, the bottle could be exposed to different conditions depending on where it travels or how it is sold. For these reasons, it is critical to have objective criteria that can define the suitability of a wine to be aged in the bottle, and that can warn of the implicit risks associated to that particular wine.
The main chemical processes that take place during bottle ageing with a major influence on the odor and taste profile are:
- The formation/disappearance of fruity aroma esters
- The formation/disappearance of varietal aromas as a consequence of the equilibrium with their precursors
- The formation/release of aromas in chemical reduction processes (oxygen deficiency)
- The formation of dimethyl sulfide (DMS) as a consequence of the hydrolysis of its precursor
- The formation/degradation of aromas in oxidation processes (oxygen presence)
Basically, each wine has a fixed capacity for aromatic expression based on its content in precursors. There are inherent risks of reduction problems, losing freshness and developing oxidation aromas. These are also consequences of the chemical composition of the wine. Therefore, each wine has an optimal window for ageing, defined by time, oxygen contact and temperature.
Our lab has rational criteria for determining how the wine is going to evolve, its optimal date for consumption and the most suitable ageing parameters for achieving the desired organoleptic profile.
Do you want to know if your wine can fulfill its varietal potential?
Do you want to know if your wine is going to generate reduction aromas and at what rate?
Do you want to know if your wine is going to generate oxidative aromas and at what rate?
- Application of Aroma Science to the home appliance industry
The technological innovations developed in home appliances are designed to make the lives of users in the kitchen easier, safer and more enjoyable. Housework is more pleasant in the absence of bad odors. This is why our scientific knowledge of aroma chemistry and analytical strategies are very useful in the development of the home appliance industry.
In spite of the large number of advantages associated with the use of home appliances, sometimes problems can occur such as the appearance of microorganisms or the generation of off-flavors (in fridges, washing machines or dishwashers). Thanks to our research, we know the chemical compounds responsible for these odors and their contents under different conditions. This knowledge is essential for proposing and carrying out innovative developments related with volatile compounds and aromas in different domestic appliances.
One of the latest advances implemented in some appliances (ovens, dishwashers) is the introduction of a cleaning program. In ovens, this program can generate a characteristic and unpleasant odor in the kitchen. Our research aims to address these situations and find practical solutions.