Bloom (test)
Bloom is a test used to measure the strength of a gel, most commonly gelatin. The test was originally developed and patented in 1925 by Oscar T. Bloom. The test determines the weight in grams needed by a specified plunger to depress the surface of the gel by 4 mm without breaking it at a specified temperature. The number of grams is called the Bloom value, and most gelatins are between 30 and 300 g Bloom. The higher a Bloom value, the higher the melting and gelling points of a gel, and the shorter its gelling times. This method is most often used on soft [gelatin capsule]s. To perform the Bloom test on gelatin, a lab keeps a 6.67% gelatin solution for 17–18 hours at 10 °C prior to testing it.
Various gelatins are categorized as "low Bloom", "medium Bloom", or "high Bloom", but there are not universally defined specific values for these subranges. Gelatin is a biopolymer material composed of polypeptide chains of varying length. The longer the chain, the higher the Bloom number:
| Category | Bloom number | Average molecular mass | Examples |
| Low Bloom | 30–150 | 20,000–25,000 | Beef hide low Bloom gelatin |
| Medium Bloom | 150–225 | 40,000–50,000 | Gelatin type B |
| High Bloom | 225–325 | 50,000–100,000 | Gelatin type A |