Bloom is a test to measure the strength of a gel or 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 (normally with a diameter of 0.5 inch) 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 gels. To perform the Bloom test on gelatin, a 6.67% gelatin solution is kept for 17–18 hours at 10 °C prior to being tested.
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|
- "US1540979 Machine for testing jelly strength of glues, gelatins, and the like". Google Patents. Retrieved 1 September 2016.
- Schrieber, Reinhard; Gareis, Herbert. Gelatine Handbook: Theory and Industrial Practice. Wiley. ISBN 978-3-527-61097-6.
- "Gelatins—product information sheet" (PDF). Sigma-Aldrich. Retrieved 24 August 2017.
- Phillips, Glyn O.; Williams, Peter A. (2000). "6.3.1. Bloom strength—standard method for characterizing gel strength". Handbook of Hydrocolloids. Taylor & Francis. ISBN 9780849308505.
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