The ISO 8156 standard, published by the International Standards Organization (ISO), describes the method of determining the insolubility index as a tool to evaluate the solubility of instant or not dried whole milk, dried partially skimmed milk and dried skim milk.
This method can also be applied to dried whey, dried buttermilk and dried milk-based baby foods, as well as any dried product where milk fat is replaced with another fat or dried in a cylinder instead of a spray.
For the purposes of this standard, the insolubility index is the volume, in milliliters, of the residue (insoluble residue) obtained when a dried milk or dried milk product is reconstituted and the reconstituted milk or dairy product is centrifuged under the conditions specified in this standard.
During the test, water at 24 degrees or 50 degrees if appropriate is added to a reconstructed test section using a special mixer. After a certain waiting time, a certain volume of reconstituted milk or dairy product is centrifuged in a graduated tube. The liquid in the precipitate is removed and the sediment is redistributed after adding water of the same temperature as that used for dilution. The mixture is centrifuged and the resulting volume of residue (insoluble residue) is recorded. Only distilled water, demineralized water, or at least water of equivalent purity is used for this test.
Generally speaking, the insolubility index is a measure of a powder's ability to dissolve in water. It is defined as the volume of sediment in ml after centrifugation. This method is normally used for skim milk, whole milk and sweet buttermilk powder, but it is also applied to other soluble, dried dairy products.
In fact, there are several fairly detailed gravimetric methods for determining the solubility of dry milk. However, for routine purposes including grading, the most commonly used procedure is the resolution index method.
Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides testing services for the determination of the insolubility index in dried milk and dry dairy products, within the scope of ISO 8156 standard, with its trained and expert staff and advanced technological equipment.
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