Location: Horticultural Crops Production and Genetic Improvement Research Unit
Project Number: 2072-21000-057-011-G
Project Type: Grant
Start Date: Aug 1, 2020
End Date: Dec 31, 2023
Objective:
1) To understand changes in white wine during oxidation and assess the ability of the e-tongue to track these changes.
2) To explore the application of the e-tongue to distinguish among potentially faulted white wines, including wines contaminated with Washington-wine isolated cultures of Lactobacillus, Acetobacter, and the non-Saccharomyces yeasts Hanseniaspora uvarum and Pichia anomala.
Approach:
To understand changes in white wine during oxidation and assess the ability of the e-tongue to track these changes, a young (prior to ageing) Chardonnay will be obtained and will undergo accelerated oxidation. Wine samples will be stored in the dark at 55°C, with samples removed daily over a period of 10 days. A control sample will be maintained at 4°C. At each time point, these wine sample will be evaluated using trained sensory evaluation panel for a pre-determined series of attributes. The GC/MS will be used to quantify volatile compounds. Browning will be measured through spectrophotometry. Also at each time point, the taste attributes of the wine samples (sweetness, umami, metallic, bitterness, sourness, and spiciness/savoury) will be analyzed using the Astree II electronic tongue unit equipped with a liquid auto sampler. Triplicate determinations will be performed for each sample. The trained panel sensory evaluation data will be included in the analysis of the e-tongue data to determine the strength of agreement between the e-tongue and these other metrics. Through statistical analyses, including principal components and correlation analyses, these results will indicate how well the e-tongue data relates the oxidative changes in the wine over time. In addition to the accelerated study, oxidation in white wines stored under regular wine storage conditions will also be conducted. White wine will be sealed with cork caps and excessive headspace, then stored at 30°C for aging. Samples for testing will be collected at one, two weeks, one, two, four, six, and nine months. The tests that will be conducted are the same as listed for the spoilage organism study below.
In order to explore the application of the e-tongue to distinguish among faulted white wines, protocols will be followed to isolate, culture and inoculate Chardonnay with either Acetobacter or Lactobacillus. In the wine, growth of the different organisms will be monitored, with samples removed weekly. At each time point, chemical analysis for volatile acidity will be performed. The GC/MS will be used to quantify ethyl acetate and other volatile compounds while the HPLC will be used to quantify acetic acid. These wines will also be evaluated by a trained sensory evaluation panel to describe the sensory changes that are occurring in the wine. Also at each time point, the taste attributes of the wine samples will be analyzed using the e-tongue. The trained panel sensory evaluation data and the chemical analyses will be included in the analysis of the e-tongue data to determine the strength of agreement between the e-tongue and these other metrics. Through statistical analyses, including principal components and correlation analyses, these results will indicate the strength of correlation between the e-tongue data and the other indications (sensory and chemical) of Lactobacillus, Acetobacter, H. uvarum and P. anomala contamination. Signature profiles of the faulted wines, in contrast to control wines, will be generated.
