MFA results (Figure 1
) show that retronasal aroma is playing a role with mouthfeel perception, especially since the majority of reapplications were sorted together (Figure S1
). The wines that were sequentially inoculated were found spatially closer together than those that were co-inoculated (Figure 1
). Specifically, teatment 1, 2 and 4 wines were perceived to be very similar and the +R and −R for each of these wines were located near each other. The +R and R for treatment 5, 6, 7 and 8 wines were not located near each other and were therefore perceived differently when retronasal aroma was removed. Treatment 3 wine is in between, as it is fairly close along F1 but is separated by F2. This would suggest that the aromas produced during co-inoculation have a greater impact on perception of mouthfeel, while the aromatics of the sequentially inoculated wines were more similar, although it should be noted the aromas of the wines were not analyzed in this study. But since the only difference in the analysis of wines was the presence of retronasal aroma, the results show that there is some influence of retronasal aroma to mouthfeel perception. This is supported by previous research where aroma was found to influence wine texture [29
]. The application of this research in other food systems has demonstrated similar results [30
], however these interactions have yet to be demonstrated in a wine matrix.
3.2. Ultra-Flash-Profiling (UFP)
Many terms used were spatially located in a similar area for both the +R and −R analysis. This suggests that while slightly different terms may be used, the panelists were describing a similar mouthfeel parameter. For instance, in −R, both bitter and tannin/phenolic were spatially located together and these two terms are known to be associated with phenolic compounds in wine [34
]. Other terms were not as consistent, for example, low and high mouthfeel, in the +R group (Figure 2
). In the −R group, astringent, dry and unbalanced were located quite close together (Figure 2
). This may be due to the individual’s difference in mouthfeel intensity, but it also suggests that panelists are using different language for a similar sensation. Interestingly the term medium mouthfeel was found to be important for −R and yet only low and high mouthfeel were found in the +R analysis (Figure 2
). This again supports the possibility that perception of mouthfeel is linked to retronasal qualities and it is perhaps the aromatic extremes or unbalances more than compositional differences that are important within a similar wine style. Clearly, there is much work needed to develop consistent terms for specific mouthfeel parameters.
The separation of specific taste and mouthfeel descriptors known to be related, and those known to be opposites, are important to note. Specifically, sweetness and dry are located in opposite directions along the F1 axis in +R (Figure 2
). These two attributes are related to residual sugar content with sweet wines having more residual sugar and dry wines less residual sugar. Sweetness and rich are also both found on the positive direction of F1. These two descriptors have been found to be related although sweetness is not the only factor attributed to richness, as fats, proteins and polysaccharides have been found to play a role in “rich mouthfeel” of other foods [35
]. We can see that terms that have a known relationship to chemical composition are being perceived in an expected manner. Although the small difference between low and high mouthfeel for +R suggests that there is either difficulty in determining what low and high mouthfeel is or that several interactions occur for lower mouthfeel wines that are not directly related to the same compositional elements.
Differences in the usage of terms between +R and −R analysis are most likely due to the influence of retronasal aroma to mouthfeel. Specifically it would appear that retronasal aroma is in fact very important for several mouthfeel associated descriptors. Terms found in +R and not −R include flabby, fresh, smooth, soft, prickly, high mouthfeel, sting and salty (Table 1
). Several of these terms are known to be in some way related to aroma or taste. For instance, salty is considered to be a taste caused by ions in the wine that are then perceived in the taste bud [36
]. However, salty is also thought to be a component of the aroma term minerality [37
] and the perception of saltiness has been found to be linked to aromas in other foods and model solutions [39
]. It appears that while salty is considered a taste, the panelists were relating it to a retronasal aroma. Fresh is another term that appears to be related to retronasal aroma, as it was incorporated in the +R analysis but not in the −R. The term “fresh” is typically related to fresh fruits or clean aromas and while aromatic information was not collected it would seem that the usage of this term may be due directly to aroma since it was not used in −R analysis.
A number of terms used in the +R analysis are not known to be linked to retronasal aroma. These include flabby, smooth, soft, prickly, high mouthfeel and sting (Table 1
). These terms are clearly related to tactile sensations. One possible explanation for their usage in +R and not in −R is that there is little consensus on the use of these terms. However flabby, flesh, smooth and soft were used between five and eight times, while the others were used less. The usage of terms with retronasal aroma suggests that an aroma is eliciting a response to these tactile sensations and that while there is no actual perception of smooth, the aroma is reminding the taster of something that can be described as “smooth”. These types of interpretations around associative learning are well known in sensory science [41
]. A further investigation into these terms and the role of retronasal aroma would be of great interest as these results clearly show the impact that retronasal aroma is having to mouthfeel. Determining which mouthfeel terms are due to a combination of retronasal aroma and mouthfeel would be extremely valuable when trying to establish chemical relationships to mouthfeel terms.
Another interesting point in the UFP analysis is that the use of terms associated with taste descriptors are used most frequently (Table 1
). This may be due to the fact that it is possible to train individuals to recognize sweetness, acidic, alcohol and bitter by the use of chemical standards [43
], making it easier for the taster to use and perceive these tastes. Familiarity with taste perception may also explain the usage of these terms, as taste is a part of all food and beverages, while mouthfeel will vary depending on the product. Additionally, panelists used two terms that are not actual sensory perceptions but chemicals, tannin/phenolic and alcohol. The tannin/phenolic terms would appear to be related to the tannin and/or phenolic content of the wine, as these compounds are known to impact mouthfeel perception [3
]. However, it is interesting to discuss the “alcohol” term. This could be referring to a sensory perception of heat, as higher alcohol content is known to producer warmer or hot wines [45
]. However, the term alcohol could also related to the smell of alcohol which is many times referred to as solvent or lifted. There are many alcohols present in wine beyond ethanol and the usage of this term and not the term “heat” warrants further investigation. It is most likely that these terms were used as they are common in most winemakers’ professional vocabulary and would not necessarily be used if panelists were wine consumers.