Understanding Quality of Pinot Noir Wine: Can Modelling and Machine Learning Pave the Way?

Wine research has as its core components the disciplines of sensory analysis, viticulture, and oenology. Wine quality is an important concept for each of these disciplines, as well as for both wine producers and consumers. Any technique that could help producers to understand the nature of wine quality and how consumers perceive it, will help them to design even more effective marketing strategies. However, predicting a wine's quality presents wine science modelling with a real challenge. We used sample data from Pinot noir wines from different regions of New Zealand to develop a mathematical model that can predict wine quality, and applied dimensional analysis with the Buckingham Pi theorem to determine the mathematical relationship among different chemical and physiochemical compounds. This mathematical model used perceived wine quality indices investigated by wine experts and industry professionals. Afterwards, machine learning algorithms are applied to validate the relevant sensory and chemical concepts. Judgments of wine intrinsic attributes, including overall quality, were made by wine professionals to two sets of 18 Pinot noir wines from New Zealand. This study develops a conceptual and mathematical framework to predict wine quality, and then validated these using a large dataset with machine learning approaches. It is worth noting that the predicted wine quality indices are in good agreement with the wine experts' perceived quality ratings.

In-mouth attributes driving perceived quality of Pinot noir wines: Sensory and chemical characterisation.

We investigated perception of mouthfeel in Pinot noir wines and its physicochemical determinants. Seventeen wine professionals judged 18 Pinot noir wines via two tasting tasks, Descriptive Rating and Directed Sorting, the latter based on perception of in-mouth attributes. Selected chemical measures of the same 18 wines were determined. Sensory results demonstrated that mouthfeel attributes driving high quality were smoothness/silky/velvety, volume/fullness/roundness, overall body, and viscosity/mouth-coating, while the taste of bitterness and perceived tannin harshness drove low quality judgments. Perceived astringency and expressions of tannin (e.g., soft; harsh; fine) drove sorting behaviour of participants. Partial least squares regression (PLSR) was used to associate perceived in-mouth phenomena and chemical composition. The phenolic profile, in particular tannin concentration and structure, was the most important predictor of astringency and its sub-components. These results have important implications for wine producers aiming to enhance perceived quality in their Pinot noir wines.

Perception of quality and complexity in wine and their links to varietal typicality: An investigation involving Pinot noir wine and professional tasters.

Quality and complexity are abstract terms employed frequently to describe a wine's overall attributes. In the present study, we investigated: (i) attributes driving wine professionals' judgments of quality and complexity in Pinot noir wines; (ii) the relation between these two abstract concepts; and (iii) association of each concept with varietal typicality. Twenty-two wine professionals evaluated 18 New Zealand Pinot noir wines in both clear and opaque glassware via two sensory tasks, a descriptive rating task and an 8-attribute, perceived complexity questionnaire. Sensory data were associated with wine UV-spectrophotometry colour measures to aid interpretation of the influence of tasting-glass colour. Results demonstrated the key drivers of perceived quality were descriptors varietal typicality, expressiveness, overall structure, and attractive fruit aromatics, along with complexity questionnaire attributes of harmony, balance and number of identifiable flavours. Reductive notes drove low-quality judgments. Data show that quality and complexity were positively associated concepts and that both were linked positively with varietal typicality. Visual influence was not a major driver of wine professionals' judgments but being able to see a wine's colour influenced tasters' judgments to wines at each end of the price/quality spectrum. We discuss the results in terms of cognitive phenomena associated with judgments by those with domain-specific expertise.

Demystifying wine tasting: Cognitive psychology's contribution.

Over recent decades, cognitive psychology has made a significant contribution to our understanding of wine-tasting phenomena. At the most fundamental level the discipline's contribution has made us aware that even an apparently 'simple' judgment, such as noting that a wine's odour reflects over-ripe fruit, involves not just our nose but sophisticated cognitive processing. With its information-processing model of how people interact with their surrounding world, and its methodologies and theories regarding how we perceive, conceptualise, remember, image, make judgments, and communicate our experiences, cognitive psychology has markedly advanced our understanding of wine tasting and wine tasters. This review highlights notable wine sensory research outcomes that make evident the importance of a taster's cognitive processes in their wine analysis and appreciation. These include data providing evidence for colour-flavour perceptual bias, prototypical thinking, knowledge-based wine judgments, the close links between olfactory memory, autobiographical memory and emotion, and the notion of wine expertise. Further, it will be argued that such data demonstrate how a consensus model, still dominant in much wine sensory analysis, is limited at best and inappropriate for sensory analysis of complex products such as wine in many contexts. Critical to this argument is appreciating that differences amongst tasters, reflecting each individual's physiology, experience and knowledge, are valid data in themselves rather than 'error in the machine' as they were conceptualised within traditional consensus models of sensory analysis. The article terminates with reference to a promise for even greater understanding of wine tasting phenomena that the future offers by links between cognitive psychology's behavioural data and recent technological advances in neuropsychology and neurophysiology (e.g., cerebral imaging techniques).

Contribution of cross-cultural studies to understanding wine appreciation: A review.

People from different cultures or geographical regions vary significantly in terms of their food and beverage consumption patterns, preferences, and purchase choices. Recent decades have seen cross-cultural research in food science flourish with research programmes in fields as diverse as perception science, conceptual behaviour, health sciences, and marketing. In this review, we describe cross-cultural research that has contributed to our understanding of wine appreciation. We begin by providing a brief historical perspective, and then outline the types of studies and methodologies employed in cross-cultural wine sensory research. We then review systematically cross-cultural studies concerning intrinsic wine factors, extrinsic wine factors, cerebral representation studies and those investigating attitudes and opinions about wine, and cross-cultural research addressing emotional response to wine. Finally, we bring together the major results reported from the varying methodologies to discuss how a cross-cultural approach can help advance our understanding of wine appreciation. We also raise contemporary issues relevant to traditional ways of defining and investigating culture in light of increasing globalisation. This review is relevant for wine industry marketing strategists as well as for those interested in the science of wine tasting.

Expectation or Sensorial Reality? An Empirical Investigation of the Biodynamic Calendar for Wine Drinkers.

The study's aim was to investigate a central tenet of biodynamic philosophy as applied to wine tasting, namely that wines taste different in systematic ways on days determined by the lunar cycle. Nineteen New Zealand wine professionals tasted blind 12 Pinot noir wines at times determined within the biodynamic calendar for wine drinkers as being favourable (Fruit day) and unfavourable (Root day) for wine tasting. Tasters rated each wine four times, twice on a Fruit day and twice on a Root day, using 20 experimenter-provided descriptors. Wine descriptors spanned a range of varietal-relevant aroma, taste, and mouthfeel characteristics, and were selected with the aim of elucidating both qualitative and quantitative aspects of each wine's perceived aromatic, taste, and structural aspects including overall wine quality and liking. A post-experimental questionnaire was completed by each participant to determine their degree of knowledge about the purpose of the study, and their awareness of the existence of the biodynamic wine drinkers' calendar. Basic wine physico-chemical parameters were determined for the wines tasted on each of a Fruit day and a Root day. Results demonstrated that the wines were judged differentially on all attributes measured although type of day as determined by the biodynamic calendar for wine drinkers did not influence systematically any of the wine characteristics evaluated. The findings highlight the importance of testing experimentally practices that are based on anecdotal evidence but that lend themselves to empirical investigation.

Perceived minerality in sauvignon blanc wine: Chemical reality or cultural construct?

The study aimed to determine the relationship between perceived mineral character in wine and wine chemical composition. We investigated the sensory properties and chemical composition of sauvignon blanc wines from two major sauvignon-producing countries, New Zealand and France. Sensory experiments employing 16 wines (8 French, 8 New Zealand) were conducted in Marlborough, New Zealand and in three regions of France, namely Bordeaux, Burgundy, and the Sancerre/Loire region. Wine professionals (31 New Zealanders and 32 French professionals) sensorially characterised the 16 wines under three conditions, bouquet only (ortho-nasal olfaction), palate only (nose clip condition), and full tasting (global condition: ortho-nasal olfaction, retronasal olfaction, taste, trigeminal stimulation). Sensory data from the global condition only are reported in this article. Physical and chemical analyses conducted on all wines included wine standard parameters, elemental composition, volatile aroma composition, and measures of organic acids. Major results demonstrate that (i) on average French and New Zealand wines were perceived similarly in intensity of mineral character, although judgments to individual wines differed as a function of participant culture; (ii) French and NZ participants drew on different information to make their sensory judgments; and (iii) several aspects of wine composition associated positively with perception of mineral character while others associated negatively, the significant associations differing as a function of participant culture.

Demystifying wine expertise: olfactory threshold, perceptual skill and semantic memory in expert and novice wine judges.

We investigated recognition and identification of wine-relevant odours as a function of domain-specific expertise. Eleven wine experts and 11 wine novices participated in tasks measuring olfactory threshold, odour recognition, odour identification, and consistency of odour naming. Twenty-four wine-relevant odorants were sampled orthonasally by each participant in the semantic (identification; consistency of naming) and episodic (recognition) memory tasks. Results showed superior olfactory recognition by expert wine judges, despite their olfactory sensitivity and bias measures being similar to those of novices. Contrary to predictions based on reports of an association between odour memory and semantic processing, wine experts did not perform better than novices on the verbal memory tasks. Further, ability to recognize odours and ability to name odours were not positively correlated, although the novices' data showed a trend in this direction. The results imply that the source of superior odour recognition in wine experts was not enhanced semantic memory and linguistic capabilities for wine-relevant odours. One interpretation of the data is that wine experts were less susceptible than wine novices to verbal overshadowing. When forced to identify the odorants, experts' superior perceptual skills protected them from verbal interference, whereas novices' generated verbal representations of the odours were emphasized at the expense of the odorant itself. This has implications for training in wine-evaluation skills.