This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
The vessels, faucets, syrup pumps, bottles, demijohns, in short all the apparatus and instruments used during the operations in preparing syrups, should be scrupulously clean and afterwards carefully washed and dried.
Wooden vessels should never be used under any circumstances, as the pores of the wood absorb and retain syrup, which it is difficult to clean out thoroughly, and is liable at any moment to undergo aceteous or other fermentation. The cellulose of the wood provokes the latter.
Galvanized iron tanks are unfit for syrup. Zinc is affected by water, and syrup is still more likely to become contaminated when brought in contact with galvanized iron vessels, of which zinc is the coating or wash.
Tin vessels for keeping syrups a long time should be avoided. If kept therein, syrups will contract a styptic, metallic taste and odor which is readily discernible, notably in the case of lemon and vanilla syrups.
The rich fragrance of extract of vanilla was thus transformed into a disagreeable sulphurous fishy odor by being kept for a certain length of time in a tin can.
During the process of manufacturing sugar or syrups there is more or less alkaline matter, including organic salts of lime, which require to be neutralized by treatment with sulphuric acid. In consequence of this, more or less superfluous acid is apt to remain, which, if brought in contact with tin or with tinned vessels containing lead, produce very serious injury to the health of the consumer.
Most syrups are acidulated by the addition of lime juice (which is only too often manufactured from a mixture of tartaric, acetic and sulphurous acids), or by citric or tartaric acids, and although the quantities of the acids used are not, in many cases, sufficient to produce an immediate action upon the tin, their influence is nevertheless very sensible, and will often manifest itself by a styptic, metallic taste, which is anything but agreeable. Syrup, as well as molasses, contains naturally a small proportion of the following acids, viz.: Formic acid, acetio acid, arabinic acid, propionic acid, butyric acid, and also nitrogenous substances, such as asparagin, glutaminic acid and betain. As all these substances have a decided action on tin, they should never, under any circumstances, be kept in tin or tinned vessels.
Silver-lined copper vessels are well adapted for storing syrups, but too expensive.