Gelatin is a differential medium which tests the ability of an organism to produce an exoenzyme, called gelatinase (this enzyme hydrolyzes gelatin)
When gelatin is at a temperature below 32°C (or within a few degrees thereof), it is a semisolid material and at temperatures above 32°C, it is a viscous liquid
When gelatin is broken down, it can no longer solidify and if an organism can break down gelatin, the areas where the organism has grown will remain liquid even if the gelatin is refrigerated
No the conclusion by student is not right because the tube must be runny after incubation followed by refrigeration to be considered gelatinase positive
