*2.2. VOO Samples*

Each sensory panel (EU, IT, IP, UN, UP/ZRS, UZ) was responsible for the sampling (two years: 2016–2017 and 2017–2018 olive harvest seasons) of a possibly balanced number of extra virgin (EV), virgin (V), and lampante (L) samples defined by sensory evaluation, according to EU Regulations [8] and later modifications.

These samples were collected to be representative of the most common olive cultivars, different geographical origins (without restrictions to the national market of each sensory panel), different sensory profiles and, especially, the main sensory defects perceived. Samples were directly requested from olive oil companies under a nondisclosure agreement containing information related to responsibility and confidentiality of data. The selection of the sample set for each year was based on sensory screening: each panel leader, assisted by his/her deputy panel leader, was responsible for applying the official procedure for assessing the organoleptic characteristics of VOOs (according to [8] and later modifications). At the end of the sensory screening, panel leaders sent the results of sample screening to the UNIBO panel leader.

Each olive oil company that agreed to participate in the sampling phase had to provide information related to each commercial sample furnished (date of sampling, geographical origin of olives, olive variety/varieties, PDO, PGI, sanitary state of olives, time and storage conditions of olives before milling, mill location, technology parameters, date of production of the oil, date of start of oil storage, type of storage tank/bottles, oil storage temperature). The need to collect all available information on each sample was the reason why samples were requested from companies, avoiding collection directly on the market. However, the oils collected were representative of possible commercial samples and also so-called borderline samples that can be the object of disagreement between panels in terms of sensory characteristics. The olive oil company indicated a person who was responsible for oil sampling among its employees, who followed and applied guidelines for oil sampling [23,24].

For each sample, a volume of 7 L was requested from the olive oil company and collected inside adequate tins or bottles. In case of a batch produced and packed (oil already bottled), the responsible person selected by the olive oil company had to collect the volume required (7 L) taken with a random selection of bottles. The panel leader assisted by his/her deputy panel leader was responsible for managing the laboratory samples. The olive oil company dispatched the packaged samples to the panel leader, who organized the preparation of laboratory samples (after proper homogenization, using a 0.5 L tin), their label codes, and shipment to all the OLEUM partners involved (carried out in the shortest time possible by tracked shipments). Sample codes summarized the basic information: partner acronym (responsible for the sampling) and number (progressive for two years, related in unique way for each sample).

The samples collected for each year (first year, 180 oils; second year, 154 oils) were divided into four subgroups and their sensory evaluation as well as sensory results were planned over time by the UNIBO panel. All samples, stored in the lab at 10–12 ◦C, were reconditioned at room temperature for 6–8 h before preparing samples for sensory analysis.

## *2.3. Sensory Analysis*

The panel test method was carried out using six OLEUM panels. Positive and negative descriptors were evaluated according to the official procedure ([8] and later modifications). The intensity of each attribute was graded by assessors using a continuous unstructured line scale of 10 cm. Each 15 mL sample was tasted at 28 ± 2 ◦C in a tasting booth, regulated in terms of shape and equipment [4]. Each panel leader collected the profile sheets completed by each taster (8–12) from his/her panel, reviewed the intensities assigned to the different attributes, and inserted the sensory data in the IOC Excel program for statistical elaboration based on the calculation of the median. The robust coefficients of variation (CVr%) were calculated and validated ([8] and later modifications).

Moreover, with the aim to monitor and possibly improve the performance of panels, after elaboration of each subgroup of sample data, the UNIBO panel, being responsible for the sensory activities, adopted and applied the quality control procedures to check the validity of the results obtained by OLEUM panels in agreement with IOC guidelines for the quality control of virgin olive oil panels revised in 2018 [25], specifically: (i) z-score estimation was conducted for each sensory panel (IOC z-score and OLEUM z-score) to estimate the panel's trueness; (ii) available IOC standards and other materials characterized (samples from previous IOC proficiency tests) were provided to each panel for training purposes; (iii) replicate analysis of three samples selected between the entire set of samples, to estimate panel precision, was performed.
