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Sensing free sulfur dioxide in wine.

Monro TM, Moore RL, Nguyen MC, Ebendorff-Heidepriem H, Skouroumounis GK, Elsey GM, Taylor DK - Sensors (Basel) (2012)

Bottom Line: These processes and others consume the SO(2) over time, resulting in wines with little SO(2) protection.This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte.We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time in situ wine monitoring.

View Article: PubMed Central - PubMed

Affiliation: Institute for Photonics & Advanced Sensing and School of Chemistry & Physics, The University of Adelaide, Adelaide, SA 5005, Australia. tanya.monro@adelaide.edu.au

ABSTRACT
Sulfur dioxide (SO(2)) is important in the winemaking process as it aids in preventing microbial growth and the oxidation of wine. These processes and others consume the SO(2) over time, resulting in wines with little SO(2) protection. Furthermore, SO(2) and sulfiting agents are known to be allergens to many individuals and for that reason their levels need to be monitored and regulated in final wine products. Many of the current techniques for monitoring SO(2) in wine require the SO(2) to be separated from the wine prior to analysis. This investigation demonstrates a technique capable of measuring free sulfite concentrations in low volume liquid samples in white wine. This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte. We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time in situ wine monitoring.

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Chemical structures of the four compounds produced throughout the pararosaniline reaction and its corresponding colors. (a) Pararosaniline hydrochloride; (b) Acidified pararosaniline; (c) Pararosaniline working solution; (d) Sulfonic acid mixture with model wine with 30 ppm sulfite solution in a 1:1 ratio.
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f4-sensors-12-10759: Chemical structures of the four compounds produced throughout the pararosaniline reaction and its corresponding colors. (a) Pararosaniline hydrochloride; (b) Acidified pararosaniline; (c) Pararosaniline working solution; (d) Sulfonic acid mixture with model wine with 30 ppm sulfite solution in a 1:1 ratio.

Mentions: Pararosaniline hydrochloride forms a bright magenta solution (Figure 4(a)) when dissolved in aqueous solution. Upon acidification with hydrochloric acid, the solution is essentially bleached due to diminished conjugation resulting in a pale biscuit colored solution (Figure 4(b)). The addition of formaldehyde results in initial formation of the iminium ion and affords a pale purple solution (working solution) (Figure 4(c)), which reacts extremely readily with sulfites to ultimately form the highly conjugated alkyl amino sulfonic acid (colored solution) (Figure 4(d)) as a rich purple solution which has a peak absorbance between 550 and 560 nm.


Sensing free sulfur dioxide in wine.

Monro TM, Moore RL, Nguyen MC, Ebendorff-Heidepriem H, Skouroumounis GK, Elsey GM, Taylor DK - Sensors (Basel) (2012)

Chemical structures of the four compounds produced throughout the pararosaniline reaction and its corresponding colors. (a) Pararosaniline hydrochloride; (b) Acidified pararosaniline; (c) Pararosaniline working solution; (d) Sulfonic acid mixture with model wine with 30 ppm sulfite solution in a 1:1 ratio.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472855&req=5

f4-sensors-12-10759: Chemical structures of the four compounds produced throughout the pararosaniline reaction and its corresponding colors. (a) Pararosaniline hydrochloride; (b) Acidified pararosaniline; (c) Pararosaniline working solution; (d) Sulfonic acid mixture with model wine with 30 ppm sulfite solution in a 1:1 ratio.
Mentions: Pararosaniline hydrochloride forms a bright magenta solution (Figure 4(a)) when dissolved in aqueous solution. Upon acidification with hydrochloric acid, the solution is essentially bleached due to diminished conjugation resulting in a pale biscuit colored solution (Figure 4(b)). The addition of formaldehyde results in initial formation of the iminium ion and affords a pale purple solution (working solution) (Figure 4(c)), which reacts extremely readily with sulfites to ultimately form the highly conjugated alkyl amino sulfonic acid (colored solution) (Figure 4(d)) as a rich purple solution which has a peak absorbance between 550 and 560 nm.

Bottom Line: These processes and others consume the SO(2) over time, resulting in wines with little SO(2) protection.This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte.We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time in situ wine monitoring.

View Article: PubMed Central - PubMed

Affiliation: Institute for Photonics & Advanced Sensing and School of Chemistry & Physics, The University of Adelaide, Adelaide, SA 5005, Australia. tanya.monro@adelaide.edu.au

ABSTRACT
Sulfur dioxide (SO(2)) is important in the winemaking process as it aids in preventing microbial growth and the oxidation of wine. These processes and others consume the SO(2) over time, resulting in wines with little SO(2) protection. Furthermore, SO(2) and sulfiting agents are known to be allergens to many individuals and for that reason their levels need to be monitored and regulated in final wine products. Many of the current techniques for monitoring SO(2) in wine require the SO(2) to be separated from the wine prior to analysis. This investigation demonstrates a technique capable of measuring free sulfite concentrations in low volume liquid samples in white wine. This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte. We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time in situ wine monitoring.

Show MeSH