Available at: https://digitalcommons.calpoly.edu/theses/2970
Date of Award
6-2023
Degree Name
MS in Agriculture - Food Science and Nutrition
Department/Program
Food Science and Nutrition
College
College of Agriculture, Food, and Environmental Sciences
Advisor
L. Federico Casassa
Advisor Department
Food Science and Nutrition
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
Time-based sensory analysis techniques capture the dynamic retronasal and mouthfeel sensations in wines. It is important to understand how common winemaking practices and popular varietals impact the retronasal and mouthfeel profile as consumers tend to judge wine quality based on the taste, flavor, and mouthfeel of a wine. Three time-based sensory analysis methods were utilized with the objective to understand the effect of five commonly applied winemaking techniques (blending, varietal choice, fermentation temperature, cap management, and stem addition) on the dynamic retronasal and mouthfeel profile of six different varietals (Merlot, Malbec, Petite Sirah, Pinot noir, Grenache, and Tannat) grown on the Central Coast of California. An additional objective was to account for panelist salivary flow rate and its impact on the time and rate of perception of astringency and selected retronasal aromas during time-based evaluations. Finally, as descriptive analysis was employed in three of the studies to assess color and orthonasal aroma, which is an effective static method but requires a lot of training time, the use of a rapid method known as Pivot© Profile was utilized to assess Syrah wines from the Central Coast of California.
Temporal Dominance of Sensations (TDS) was utilized to determine if there were significant differences between cofermented and blended wines as well as the impact of varietal choice. TDS curves (n=11) demonstrated that varietal choice was more impactful on the retronasal profile than blending time. Chemical analysis indicated that post-malolactic fermentation wines had higher titratable acidity, while cofermented wines had higher tannins. Indeed, the differences between blending times were subtle but were reflected in the TDS curves. Therefore, it was recommended to employ post-alcoholic or post-malolactic fermentation blending over cofermentation. TDS was also utilized to understand the impact of whole cluster, stem addition, and wine sipping volume on the temporal sensory profile of Tannat wines. Similar to the previous study, TDS curves (n=10) were able to reflect differences in astringency, acidity, and hot perception which were apparent in basic and phenolic chemistry. Indeed, the combination of Tannat and stem addition led to wines with a long (34.6 seconds) perceived dominance of astringency. Volatile chemistry indicated that the use of whole cluster in Tannat wines led to higher concentrations of phenylethyl alcohol, β-damascenone, and the terpene, trans-farnesol, compared to the control, and other stem addition wines. Therefore, it was recommended to explore whole cluster addition in Tannat for future research over the green and dried stem wines.
Time-Intensity (TI) and Temporal Check-All-That-Apply (TCATA), were utilized to understand the effect of alcohol fermentation temperature and cap management regimes in Pinot noir and Grenache wines. TI results (n=13) suggested that fermentation temperature had more of an impact on the mouthfeel and retronasal profile of Pinot wines than cap management. Indeed, while Hot fermentation temperature wines led to more intense astringency perception relative to the other treatments, Cold fermentation temperature wines led to higher perception of retronasal flavor which was also reflected in the volatile chemistry. As for Grenache, the results were more complicated as this variety was sensitive to both oxidation and reduction aromas. TCATA (n=8) and volatile chemistry results indicated that the treatment with the most balance of retronasal fruit and astringency with minimal reduction flavor were the Cold/Hot PD wines. The results of both studies suggested that both fermentation temperature and cap management regime were indeed varietal dependent.
When using time-based sensory analysis, it is important to account for salivary flow rate, an inherent physiological characteristic, that affects the time and perception of astringency and retronasal aromas. Past research has utilized TI to examine this phenomenon, whereby low salivary flow rate individuals typically perceived astringency later and more intensely than high salivary flow rate individuals. For retronasal aromas, it depends on the associated volatile compound. For example, fruit aromas which are associated with esters are typically perceived by high salivary flow rate individuals as later and more intensely than low salivary flow rate individuals. Since tracking salivary flow rate has been exclusively used in TI, methods were developed in the present study to examine the time of first dominance in TDS and time of first perception in TCATA. Throughout each study, the pattern of astringency perception followed previous reports with two exceptions. In the Pinot noir wines, higher salivary flow rate panelists had their time of maximum intensity later than low salivary flow rate panelists. However, the time of first perception, maximum intensity, and area under curve were still significantly later and higher in low salivary flow rate panelists. With the Tannat wines, high salivary flow rate individuals had significantly later time of dominance for astringency than low salivary flow rate panelists. In this case, it was thought to be because only one parameter was being assessed for this pattern whereas the inclusion of area under curve or maximum citation proportion by group may provide more information.
Finally, the use of a modified Pivot© Profile with an expert panel (n=15) was examined in Syrah wines that underwent different cap management and maceration techniques as well as different ethanol levels. Results indicated that modified Pivot© Profile was effective for differentiating color and orthonasal aroma attributes by cap management style. However, modified Pivot© Profile was not able to reflect the differences seen in the basic and volatile chemistry specifically the effect of ethanol level on malolactic fermentation. Therefore, it was recommended to use modified Pivot© Profile for color and orthonasal aroma but employ a time-based sensory method for understanding the retronasal and mouthfeel profile as it can reflect differences in chemistry more effectively.
Overall, the employment of time-based sensory analysis to examine the dynamic retronasal and mouthfeel profile in red wine was worthwhile, as these methods can subtly reflect differences in chemistry as well as assist in making practical winemaking decisions.
