Sensory Evaluation Training and Wine Tasting Protocol

Eleven subjects (45% females and 65% males, 24 ± 5 years old) were recruited among the students and technical staff at the Free University of Bozen-Bolzano (Bolzano, Italy). A preliminary selection of candidates was carried out in order to choose subjects without any history of oral perception disorders and able to discriminate differences in sensory properties among samples. After a full explanation of the aim of the experiment, an informed consent was signed by suitable candidates who agreed to participate voluntarily in the subsequent training and sensory analysis sessions. The panel received a specific training on how to recognize and evaluate each sensory descriptor using intensity scales (ISO 8586:2012). The training was divided into two phases: qualitative and quantitative evaluations. The initial qualitative analysis phase consisted in presenting two ISO glasses containing two wines (one for each vinification) in order to define the range of descriptors to be used during the following sensory analysis as well as a common sensory vocabulary for visual, olfactory and gustatory evaluations. Following the qualitative analysis, a specific training program developed in sessions of approximately 60 min each (two sessions per week for eight weeks) was undertaken on the descriptors obtained previously. The recognition and classification of aroma standard solutions were performed by asking subjects to identify and recognize different aromas such as rose, orange blossom, elder flower, banana, pear, apple, green apple, lemon, plum, raisin, fig, mint, rosemary, sage, fennel, hay, honey, clove, licorice, anise, and black pepper. In addition, other solutions (alcohol and ethyl acetate) were provided to the panel as ‘pungent’ descriptors. The recognition and classification of standard samples were performed by asking the panelists to identify the taste and to order the standard solutions according to perceived intensity for each descriptor (from the lowest to the highest intensity). The subjects were instructed to use a 9-point intensity horizontal scale ranging from 1 (weak) to 9 (strong) to rate the perceived intensity for taste descriptors including salty (0.25–0.5–0.75–1 g·L⁻¹ sodium chloride), sourness (2–4–6–10 g·L⁻¹ tartaric acid), sweetness (0.5–2–5–10 g·L⁻¹ sucrose), bitterness (0.25–0.5–0.75–1 g·L⁻¹ caffeine), and astringency (0.25–0.5–0.75–1 g·L⁻¹ alum). All the standard solutions were prepared using food-grade reagents dissolved in a non-aromatic white wine. The subjects were provided with plain crackers without added salt and water and were instructed to rinse their mouth between samples during the sensory sessions.
Following completion of the training and before starting the session, panelists received by the panel leader detailed instructions on the definition of descriptors and how to conduct the sensory evaluation (sampling from the left to the right direction according to the order proposed). They were informed that the descriptors would have been related to visual evaluation (clarity and color intensity), olfactory evaluation (olfactory intensity, floral, apple, pear, tropical fruit, dried fruit, spicy, fresh vegetative, cleanness, off-odor), gustatory evaluation (warmness, sweetness, sourness, saltness, bitterness, astringency), and overall quality judgement. The complete list of descriptors is reported in the Supplementary Material (Table S2). The panel performance was assessed to check the consistency of each panelist and between panelists (data not shown), enabling the identification of assessors who were not consistent with the whole panel, therefore, his/her data was not included in the evaluation.
The wines samples were evaluated according to Quantitative Descriptive Analysis (QDA^®), which is one of the main descriptive analysis techniques adopted for sensory evaluation, under the conditions described in the UNI 10957:2003 procedure. The wine bottles were opened just before the analysis and 30 mL of wine per glass at around 16 °C were offered randomly (in triplicate) to the panelists in ISO glasses codified with a 3-digit number. The presentation order of the wine samples was randomized between and within participants.