Sulfur dioxide in wine

Sulfur Dioxide. The legal limits for total sulfur dioxide in wines varies from 200 to 350 mg/liter. In addition, the limit for sulfur dioxide not bound to aldehydes, polyphenolic compounds, etc. may be from 30 to 100 mg/liter. Winery control requires that the amount of sulfur dioxide present during processing and aging be carefully controlled, and increasing concerns for public health reinforce this. 

Bartroli, M Escalada, CJ Jorquera, J Alonso. Determination of total and free sulfur dioxide in wine by flow injectionp-aminoazobenzene as the colorimetric reagent. Anal Chem 63 2532-2535, 1991. 

F Falcone, KC Maxwell. Simultaneous continous flow analysis of free and total sulfur dioxide in wine. J Agric Food Chem 40 1355 -1357, 1992. 

M.A. Segundo, A.O.S.S. Rangel, A. Cladera, V. Cerda, Multisyringe flow system determination of sulfur dioxide in wines, Analyst 125 (2000) 1501. 

Another interesting example of the FIA stopped-flow procedure is the. determination of sulfur dioxide in wine [71], based on the well-known West-Gaeke [4.2] method, in which a purple compound formed by the... 

Azevedo, C.M.N., K. Araki, H.E. Toma, and L. Angnes (1999). Determination of sulfur dioxide in wines by gas-diffusion flow injection analysis utilizing modified electrodes with electrostatically assembled films of tetraruthenated porphyrin. Anal. Chim. Acta 3S7, 175-180. 

VIII. Sulfur Dioxide in Wine and Vinegar Making. 136... 

In addition to the iodometiic determination, direct precipitation as barium sulfate before and after treatment with bromine was suggested for both quantitative and qualitative test for sulfur dioxide in wine (see Monier-Williams, 1927). Precipitation of SO2 after oxidation with H2O1 as the benzidine sulfate was proposed by Rothen-fusser (1929) reduction of the molybdenum in phosphomolybdic acid by the sulfite ion present in an aqueous solution of the food was proposed by Sasaki (1928) as a colorimetric method formation of a blue color from a solution of 1% methylene blue and 5% iodine in potassium iodide was proposed by Svershkov (1939). Mathers (1949) proposed a turbidimetric method based on the distillation of wine into a dilute solution of lead acetate to form a colloidal suspension of lead sulfite whose spectral transmittance in the range of 400 to 700 mn could be used as a measure of sulfur dioxide. This is similar to turbidimetric methods based on turbidity produced by adding BaCfii to a... 

Total SulfuT Dioxide After Alkali Treatment The fact that neutral sodium sulfite does not combine with carbonyl compounds and that the hydroxysulfonic acid compounds are rapidly decomposed on treatment with alkali was used by Ripper (1892) as the basis for the determination of total sulfur dioxide in wine by direct iodine titration. In his method, 50 ml. of wine were pipetted into a 200-ml. flask containing 25 ml. of 1 iV KOH. The mixture was shaken and allowed to stand for 10 to 15 minutes. Then 10 ml. of dilute sulfuric acid (1 + 3) were added, and the solution titrated rapidly with 0.02 N iodine solution to a starch end point which persisted for some time. This method was used as the ofiicial direct titration method for wine in the first edition (1919) of the A.O.A.C. Methods of Analysis in the third (1930) edition it was extended to white grape juice, wine, and similar products (1N NaOH or KOH was used and the solution during standing for 15 minutes was occasionally agitated) hut it was dropped from the fourth (1935) and succeeding editions. Ripper compared his method with the Haas distillation method on ten wines whose SO2 content varied from 42 to 1488 mg. per liter and found the difference between the two to vary from 0 to 5 mg. 

In the case of musts and wines, however, additional compounds besides sugars, particularly acetaldehyde, help to bind an appreciable part of the SO2. For a long time, ever since SO2 came to be used generally in wine technology, the problem of bound SO2 occupied the minds of research workers. Rocques in 1897 maintained that SO2 in musts and wine was bound by glucose, but Ripper (1892) and Schmidt (see Kerp, 1904) thought that sulfur dioxide in wines existed in the greater part as a combination with aldehydes. 

Mathers, A. P. 1949. Rapid determination of sulfur dioxide in wine. J. Assoc. Offic. Agr. Chemists 32, 745-751. 

Mills, D. R., and Wiegand, E. H. 1942. Effect of storage on sulfur dioxide in wine. 

Sulfur dioxide is easily recognized by its characteristic smell, which irritates the respiratory passages. As already mentioned, it is mainly used for the production of sulfuric acid, but it also has some applications of its own, as it kills bacteria and is an antioxidant. SO2 or sodium sulfite preserves the natural color of fruits and vegetables -for instance, peeled potatoes remain white. Sulfite is also added to wine before bottling to prevent further fermentation. Sulfur dioxide in wines may however cause health problems. 

Among secondary products, ketonic function compounds (pyruvic acid, a-ketoglutaric acid) and acetaldehyde predominantly combine with sulfur dioxide in wines made from healthy grapes. Their excretion is significant during the yeast proliferation phase and decreases towards the end of fermentation. Additional acetaldehyde is liberated in the presence of excessive quantities of sulfur dioxide in must. An elevated pH and fermentation temperature, anaerobic conditions, and a deficiency in thiamine and pantothenic acid increase production of ketonic acids. Thiamine supplementing of must limits the accumulation of ketonic compounds in wine (Figure 2.10). 

Practical consequences the state of sulfur dioxide in wines... 

The concentration of sulfur dioxide in wine is habitually expressed in mg SO2 per liter (or ppm) although this substance exists in multiple forms in wine (Section 8.3). 

Fig. 8.2. The different states of sulfur dioxide in wine (Rib6reau-Gayon et al., 1977)...

PRACTICAL CONSEQUENCES THE STATE OF SULFUR DIOXIDE IN WINES... 

Fig. 8.6. Graphical representation of the binding of sulfur dioxide in wine at CL20, CL50 and CLICK)...

Sorbic acid therefore exerts a selective effect on wine microorganisms and opposes yeast development without blocking bacterial growth. It has the opposite effect to that of sulfur dioxide (which favors yeasts at the expense of bacteria). Consequently, sorbic acid must never be used alone but always associated with an antibacterial product (sulfur dioxide). In wines exposed to air, the amount of volatile acidity formed by acetic acid bacteria can be greater in the presence of sorbic acid, due to the absence of an antagonism with yeasts. 

Cardwell and Christophersen reported a dual channel FI system with amperometric detection for the determination of ascorbic acid and sulfur dioxide in wines and fruit juices (Cardwell and Christophersen, 2000). Here, the ascorbic acid was detected at a glassy carbon electrode polarized at 0.42 V (vs. Ag/AgCl), whereas the sulfur dioxide was detected at a Pt electrode polarized at 0.90 V (vs. Ag/AgCl) after separation of the analytes by a gas diffusion unit. The determination of ascorbic acid showed a linear range between 3 and 50 mg L with an FOD of 1.5 mg L for sulfur dioxide the linear range was between 0.25 and 15 mgF i and an FOD of 0.05 mgF" was obtained. The sample frequency achieved with the system was 30 h b The proposed method showed a good agreement with a reference method in the results obtained for white wines and juice samples, while for red wines and sweet wines an extraction procedure of the analytes by solid-phase extraction was required. 

Linares, P., M. D. L. DeCastro, and M. Valcarcel. 1989. Simultaneous determination of carbon-dioxide and sulfur-dioxide in wine by gas-diffusion flow-injection analysis. Anal. Chim. Acta 225 443-448. 

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