Determination of hydrogen peroxide (H2O2) in disinfectants.
Suitable for all solutions that contain hydrogen peroxide (H2O2) but no other peroxides.
Hydrogen peroxide oxidizes iodide to iodine, which is reduced by sodium thiosulfate (Na2S2O3) and recalculated as hydrogen peroxide.
|
H2O2 + 2 NaI +H2SO4 |
→ |
I2 + Na2SO4 + 2 H2O |
|
I2 + Na2S2O3 |
→ |
2 NaI + Na2S2O3 |
If the sample contains other peroxide-containing disinfectants in addition to hydrogen peroxide (H2O2), the method T-757-01-032 Peracetic-acid-based-disinfectants must be used.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
A specified quantity of water is evaporated, and any remaining moisture is subsequently eliminated in a drying oven. The dry residue is then weighed.
The method provides an estimate of the portion of pre-germinated barley grains at the time of harvest or prior to storage in silos.
Barley intended for the production of malt is evaluated with regard to pre-germination.
The onset of germination is accompanied by the synthesis of enzymes, which can be made visible using fluorescein dibutyrate (FDB). The reagent fluoresces in the presence of lipases.
In order to make the enzyme activity visible, the kernels are first split in half and coated with the FDB reagent after which they are examined in a suitable measuring device under UV light. An intense yellow fluorescence can be seen in the parts of the kernels where enzyme activity is present.
Malt intended for use in beer brewing or elsewhere in the food industry
Applicable for all (laboratory) worts
The Congress wort is heated in order to inactivate the amylolytic enzymes, and afterwards, yeast is added and the wort is allowed to completely ferment out at a minimum temperature of 20 °C in a fermentation tube (fig. 1). The difference in the extract before and after fermentation is measured in order to calculate the limit of attenuation.
Applicable for all (laboratory) worts
The Congress wort is heated in order to inactivate the amylolytic enzymes. Afterwards, 16 g/100 ml yeast is added, and the wort is allowed to completely ferment out in approx. 7 h.