Gelatin is an excellent growth medium for bacteria. Therefore, strict sanitary practices must be followed during manufacture in order to assure a clean, wholesome product.
Food grade gelatins typically contain less than 3,000 bacteria per gram, with no pathogens present. Pharmaceutical gelatins are limited to aerobic plate counts of 1000 per gram. The National Formulary and the Food Chemical Codex monograph on gelatin both require that Salmonella species and Escherichia coli be absent.
The gelatin molecule is not only thermally labile, but also can be degraded rather quickly by certain bacteria, diminishing both gel strength and viscosity. Consequently, care must be taken to prevent contamination during use.
As a dry powder, gelatin is very stable, and can be stored in air-tight containers for years with no loss in quality. Gelatin in solution, or soaking in water, should be left in this state only if kept very cold, or hot enough to destroy or inhibit bacterial growth.
The nature of the organisms which grow in gelatin solutions and gels depends upon a number of factors. The pH has a most important influence. At pH values less than 4, bacterial growth is suppressed, while yeasts and molds grow abundantly. Above pH 5, proteolytic bacteria can become active.
Degradation of gelatin solutions and gels by bacteria, yeasts, and molds may be inhibited by the use of preservatives. The selection of the preservative depends upon whether the product application is edible, topical, or technical. Gelatin gels generally require a greater concentration of preservative than do dilute gelatin solutions. The addition of other nutrients to the gelatin may also increase the amount of preservative required.