Tannins sulphitation

Lemonade shandy is made with shandy ale , a bitter beer brewed to 6.5% ABV to minimise transport costs. For colouring the product it is important to use an ammonia caramel as the sulphite ammonia caramels used for conventional soft drinks will react with tannins in the beer and precipitate out. 

Sodium sulphite. A crystal of this salt, placed on a flat porcelain dish, is moistened with a few drops of the tannin solution and any coloration noted. 

The presence of sulphite cellulosic liquors may be recognised, according to Procter and Hirst, by treating 5 c.c. of the dilute solution (which is used for analysis) with 0-5 gram of aniline and then, after shaking, with 2 c.c. of concentrated hydrochloric acid in presence of such liquors a precipitate is immediately formed and gradually rises to the surface. A more certain indication of the addition of sulphite cellulose liquors may, however, be obtained from a comparison of the results of the determination of the tannin by two methods—indirect and direct (see later). 

The gluing experiments were done with commercially available starch, proteins (casein, glutin) and tannins of mimosa Acacia spp.), Pinus radiatay and quebracho (Schinopsis spp.) and with tannins extracted from the bark of spruce (Picea abies) and common pine (Pinus sylvestris). The extractions were carried out with water or organic solvents under alkali and/or sulphite conditions on a laboratory scale aiming at optimization of yield and polyphenolic extract content. After extraction, the solutions were concentrated under reduced pressure and freeze dried. One pine bark extract was modified with phenol. A summary of the tannin extracts and their properties is given in Table I. 

Other reactions involving this aldehyde include the following (1) combination with sulphite ion, which substantially increases the proportion of bound sulphite in wine (2) formation of addition compounds with some polyphenols such as tannins and procyanidins, where it acts as a bridging molecule (Haslam and Lilley 1998) and (3) chemical oxidation to acetic acid, which only occurs to a small extent and has little influence on wine composition and quality. 

Pizzi A 1979 Sulphited tannins for exterior wood adhesives. Coll Polym Sci 257 37-40... 

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