08 July 2011 13:23
OIV Feature: Spinning Wheel of Flavours in Wine
July 08: Sensory evaluation of wine flavour can be objective or subjective, but both involve processing of information by the brain where perceived wine properties are compared to those previously experienced and are highly individual and perception is the key, according to Prof. Ann Noble who talked of various tasting experiments at the 34th OIV International Conference of Vine and Wine in Porto. Subhash Arora who was the lone Indian delegate reports.
‘In analytical tests, perceived wine properties are compared to those previously experienced. These interactions of taste and aroma suggest that interactions occur in the brain to produce the enhancement. Perception is also influenced in objective evaluations by factors that create an expectation, further suggesting that processing of aroma or taste perception is through a neural activity in the brain and is highly individual,’ she said.
Factors affecting Perception
Of course the concept that flavour is perceived as the result of the processing and interpretation by the brain is not new and was known in the early 20th century. While tasting wine, mood, motivation and concentration of a taster influence the perception, she said. Sensitivity to taste is greater when the taster is relaxed and able to concentrate. Motivation of the panellists tasting has been known to influence performance in sensory tests. Similarly, conducting tests under conditions in which extraneous factors and distractions were eliminated, increased sensitivity to taste or smell.
Because of the many factors other than aroma, taste and mouth-feel that influence
sensory perception, scientific methods have been developed for sensory evaluation to permit reproducible and consistent measurement of the sensory properties of wines.
These methods focus on minimizing any effects on perception that were not due to the stimuli alone. Testing is conducted under controlled conditions, designed to minimize the bias and to standardize the presentation of samples. Wines are presented to the judging tasters in random order to minimize guess work and reduce systematic effects such as adaptation, contrast or context.
It was interesting, for example, to know that if a wine low in acidity is tasted with another one that is high in acidity, it will be rated far lower in acidity than if it were presented with another wine only slightly more crisp flavour.
Eliminating Extrinsic Factors in Tasting
Marketing strategies exploit these factors to increase consumer perception of greater
value or expected enjoyment. In contrast, analytical sensory research testing removes all the extrinsic information.
Perceptions due to Colour
To evaluate the effect of experimental viticulture or oenological treatments on aroma of wines which differ in colour, the appearance of the wine should be masked by serving it in black glasses or under red light, she suggested. The need for masking colour was shown as early as 1963 in a study of unsweetened white wines coloured with red dye.
The so called experts rated the darker pink wines higher in sweetness than the lighter pink wines since they assumed the wines were rosé. Colour also affects the generation of descriptive terms for wine flavour. Student judges describing aromas of white wines coloured with red dye used more terms for red fruits and dark objects than terms associated with yellow fruits which they had used to describe the same white wine without the colouring
Effect of sweetness
The studies have suggested the interactions between taste and smell sensations.
Taste influences perceived aroma, for example. In orange-flavoured solutions fruitiness intensity ratings were higher and the sensation lasted longer when either the sourness or sweetness of the solutions was increased.
Salivary flow rate was also measured in the experiment above. Acid is known to increase the salivary flow. When sweetness was increased in the solutions with fixed acidity by adding aspartame, it resulted in decreased perceived sourness intensity.
Effect of higher viscosity
Interactions between tactile and taste sensations also have been reported. Perceived sweetness was rated higher in solutions with identical sucrose concentrations
when the viscosity was increased with a non-sweet thickener. In another study, increasing the sweetness of wine decreased the perceived astringency.
Price vs. Quality Perception
No difference in liking was found when the duplicate wines were tasted with only codes identifying them. However, increasing the price of a wine increased rating of liking or pleasantness as well as brain activity in the medial orbitofrontal cortex- an area in the brain where separate inputs from the different senses are interpreted and a unitary concept of flavour is constructed, even though the wines were identical
The flavour of wine may after all, be all in your head- was the general conclusion of her interesting presentation- one of the several dozens at the Conference-very technical and scientific in nature.
Prof Ann Noble may be contacted at firstname.lastname@example.org - editor