The Science of Appraisal
Our senses are closely coupled to our memory. Sensory appraisal utilises four of our five senses: Vision (sight), olfaction (smell), degustation (taste) and tactile (mouth feel). This could be viewed as the first stage of judging. The second stage would be the communication of impressions and assessments to others. Wines are predominantly assessed by orthonasal (sniff) or retronasal (mouth) airways. Research found differences in orthonasal and retronasal perception was strongly influenced by physical characteristics of the aroma chemicals (Diaz, 2004).
These sensory processes induce a pattern of sensations, images and memories which assist with identification. Memory involves semantic (identification) and episodic (recognition) processes. To appraise is the ability to discriminate among thousands of low molecular-weight organic compounds each with unique chemical structures and properties. This task involves a huge molecular recognition capacity.

The olfactory bulb located at the base of the brain is the first site for processing this information in the brain. More recently science has gained insight into the molecular basis of odour recognition and combinatorial coding of this complex system. Sensory neurons detect a vast array of small volatile molecules with extremely high sensitivity and specificity. Results have shown that constituent molecules and mixing ratios are simultaneously encoded into spatiotemporal activity patterns (Oyamada, Kashimori, Hashino & Kambara, 2000). Odour recognition is therefore achieved by a combination of firing patterns. A characteristic activity pattern encodes the quality of a particular odour. The stronger the response the earlier the compound is recognised: A hierarchal discrimination of an odour.

 In short chemicals are deconstructed into neural signals in the olfactory bulb and appear combined in neurons in the cortex forming widely distributed and multiplexed odour maps. Scientific principles have impacted on technical aspects of wine production and sensory evaluation through the cognitive process of learning and understanding of the complexities involved and means of improving quality.

Diaz, M. (2004). Comparison between orthonasal and retronasal flavour perception at different concentrations. Flavour and Fragrance Journal, 19 (6), p 499-504.
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Oyamada, T., Kashimori, Y., Hashino, O., & Kambara, T., (2000). A neural mechanism of hierarchical discrimination of odors in the olfactory cortex based on spatiotemporal encoding of odor information. Biol Cybern, 83 (1), p 21-33.