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. 2023 Sep 15;12(18):3450.
doi: 10.3390/foods12183450.

Thermal Desorption of 2,4,6-Trichloroanisole from Cork

Susana Monteiro  1   2 , Nenad Bundaleski  1 , Paulo Lopes  2 , Miguel Cabral  2 , Orlando M N D Teodoro  1
Affiliations

Thermal Desorption of 2,4,6-Trichloroanisole from Cork

Susana Monteiro et al. Foods. .

Abstract

While extensive efforts have been made over the past two decades to understand how cork becomes contaminated by 2,4,6-trichloroanisole (TCA), the nature of its bond to cork remains unclear. A deeper understanding of this interaction is crucial in designing processes to effectively remove TCA from cork stoppers. This study presents an investigation into the thermal desorption of TCA from cork under vacuum conditions. To facilitate detection by a quadrupole mass spectrometer, samples were artificially contaminated with sufficient TCA. A calibration system was developed to determine the absolute rate of TCA released from the cork. Desorption spectra revealed two peaks at 80 °C and 170 °C. Despite the known variability of cork, repeated measurements demonstrated reasonable repeatability. The low-temperature peak decreased with time and after preheating the sample to 50 °C. It is proposed that the high-temperature peak corresponds to TCA bonded to the cork material. Experiments with naturally contaminated cork stoppers revealed a significant reduction in the amount of releasable TCA following a vacuum-heating process. This study provides an insightful discussion on the adsorption of TCA on cork and proposes an estimate for the adsorption energy. Furthermore, it discloses a process capable of removing TCA from natural cork stoppers.

Keywords: TCA; TCA extraction; calibration method; cork stoppers; mass spectrometry; vacuum.

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Conflict of interest statement

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Authors Susana Monteiro, Paulo Lopes and Miguel Cabral were employed by the company Amorim Cork S.A. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from the Portuguese Foundation for Science and Technology (FCT). The funder was not involved in the study, design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication. Nova School of Sciences and Technology holds two patents (# WO 2018/138599 A1 and #PT109878B) authored by Orlando Manuel Neves Duarte Teodoro with royalties paid by Amorim Cork S.A.

Figures

Figure 1
Figure 1
Schematic of the experimental setup for temperature-programmed desorption experiments; the photo shows one 3 mm cork disc being pressed with a net against the walls of the oven. Valves are labeled V1–V8, flow restrictions C1–C2 and vacuum gauges G1–G3.
Figure 2
Figure 2
TCA desorption spectra from artificially contaminated cork and comparison with a clean cork (red curve).
Figure 3
Figure 3
TCA desorption spectra after 2 h under vacuum of five samples. The intensity scale was converted to mass flow rate. The legend shows the relative amount of extracted TCA.
Figure 4
Figure 4
The influence of vacuum on contaminated samples studied over time. (a) TCA desorption spectra on contaminated samples that stayed under high vacuum. Each curve is the average of 3 measurements. (b) Plot of the “lost” TCA in contaminated samples over time. Each point in (b) is the average of the area from 3 experiments, and the error bars are the standard deviation.
Figure 5
Figure 5
Study of the influence of time between contamination and analysis. (a) TCA desorption spectra of contaminated samples that stayed at atmospheric pressure in a vented space. (b) Plot of “lost” TCA; all the samples stayed for 2 h in vacuum to reach the working pressure before TPD.
Figure 6
Figure 6
Study of preheating on contaminated samples. All samples stayed for 2 h in vacuum to reach the working pressure before the TPD.
See this image and copyright information in PMC

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