title: Semi-automatic apparatus for determination of the consistency of microbiological culture media and gel-forming substances (author's transl).
abstract: The gel strength is an important factor in the production and preparation of microbiological culture media on the basis of agar-agar, silicagel and gelatine. There is an evident interest in a standardization of this parameter which can influence the number and the form of the colonies, the results of antibiograms and other tests based on diffusion. The apparatus described can be used for simultaneous determination of the gel strength and the elasticity of microbiological and industrial gels. The construction consists of an electromotor-driven supporting table for the specimen and a pressure measuring device. In operation, the gel is moved vertically with a constant speed against the probe of the pressure device. The pressure exerted on the surface of the gel can be read from a dial connected with the probe as well as the pressure at which the surface of the gel is being disrupted (breaking point, gel-strength pressure). The apparatus can be purchased under the name Gelomat from Heinrich Bareiss, 7931 Oberdischingen, West Germany (see Fig. 1 and 2). The results of the measurements can be influenced by various factors such as concentration of the gelating compound, composition and pH of the solvent, time and temperature at which the gel is held before, during and after plate pouring, surface (dry or wet) and heigth of the gel sample, method of mesurement, etc. To account for all these factors, a standard method of measurement is described. The apparatus has a sensibility of ca. 2 g, can measure a gel strength between 0 and 200 g with the standard equipment, and has a standard deviation of less than 1.35 for microbiological agar-agar gels (see Tables 2-4). The time needed for one determination is 40-60 seconds. Compared with other instruments for the same purposes, the Gelomat has following advantages: Simple and handy use, good sensitivity and reproducibility, capability for simultaneous measurement of gel strength and gel elasticity. In the last 4 years, this apparatus has been used with good results in more than 10,000 routine determinations
mesh_terms: D001431:Bacteriological Techniques / Q000295:instrumentation*; D003470:Culture Media / Q000592:standards*; D004355:Drug Stability; D004548:Elasticity; D005782:Gels
chemical_list: D003470:Culture Media; D005782:Gels
vernacular_title: Ein halbautomatisches Gerät zur Bestimmung der Gelfestigkeit mikrobiologischer Näbhböden und Gelierstoffe