Graduate Thesis Or Dissertation
 

Understanding the flavor alterations associated with smoke taint and evaluation of interstimulus protocols to mitigate carryover bias in sensory evaluation of wildfire affected wines

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2z10wz061

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  • First recorded as a problem in 2003, wildfire smoke has been found to affect wine grapes and lead to alterations to a wine’s flavor profile. Smoke can carry organic volatile compounds over vast distances, which can then be deposited on grapes and are absorbed into the grape’s cells. These compounds have been attributed to the smokey, burnt, and dirty flavors with a lasting ashy finish and excessive drying found in wines produced from smoke affected grapes. Not only are volatile compounds present in smoke, but once incorporated into the fruit they can bind with the prevalent sugars forming non-volatile glycosides. These glycosides, which are not sensorily perceptible, can then be broken down by enzymatic actions to release their perceptible aglycone. This can occur at many points, including fermentation, aging, and has been hypothesized to occur in the mouth. The in-mouth breakdown of these glycosides may lead to the strong, lingering ashy finish. These lasting sensations lead to concerns in sensory analysis due to the potential introduction of carryover bias. Carryover bias occurs when residual sensations from one sample influence the next, leading to ratings that are not truly representative of the flavor experience. In the context of smoke taint, this could lead to the incorrect identification of a sample being “tainted” due to the strong residual smoke sensations from a previous sample. With the increase in wildfire occurrence and expansion of the wildfire season, accurate sensory analysis of wildfire affected wines will be imperative to understand the full extent of sensorial alterations caused by smoke and as mitigation strategies begin to be evaluated. The studies discussed were conducted to further understand the attributes associated with smoke taint, define in-mouth flavor references, and determine optimal interstimulus protocol to mitigate carryover bias. To understand the attributes associated to smoke taint, attribute check-all-that-apply (CATA) along with temporal check-all-that-apply (TCATA) were used to evaluate three wines, representative of no, moderate, and high smoke exposure. Using these methods, the attributes that provided the most difference between the samples were identified. Additionally, the difference in temporal perception of identified smoke related attributes (Smokey, Ashy, Burnt) versus attributes more typically found in wine (Floral, Mixed Berry, Woody) was confirmed. To better define in-mouth flavor references for select attributes (Smokey, Ashy, Mixed Berry, and Floral) just-about-right (JAR) analysis was used. Due to the novelty and uniqueness of these flavors in wine, references are necessary to align panelists on the flavor sensations. From these results, the best reference solutions for panel training on the attributes found in smoke affected wine were identified. These included a diluted whiskey solution for smokey, a leek ash solution for ashy, a mixed berry jam solution for mixed berry, and a floral syrup solution for floral. For the evaluation of interstimulus protocol, six different rinse solutions were evaluated over the course of two studies using a fixed time-point evaluation procedure to determine which were effective and most efficient. These rinses included a standard water rinse, a pectin solution, an antimicrobial mouthwash pre-rinse, an ethanol solution, a lipid solution, and a glucose solution. The purpose of rinsing and time separation during sensory evaluation is to return the mouth to baseline conditions to ensure that there are not residual sensations remaining in the mouth, therefore introducing carryover bias. From evaluating these rinses, it was determined that a 4 g/L glucose solution, followed by water, with 90 seconds of separation between samples is effective in clearing the mouth of smoke related flavors. Overall, the experiments in these studies were able to provide insights into the nature of the sensorial implications of wildfires on wine. Additionally, optimal methodologies to ensure accurate and efficient analysis of these wines to limit biases from sensorial carryover were better defined. As the wildfire occurrence continues to increase, the results from this work will better guide the sensory evaluation of these wines from both a research and industry standpoint.
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  • USDA-Agricultural Research Service (ARS) Project Number 2072-2100-057-00D
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