This method describes how to evaluate the degree of contamination or the purity of malt as part a manual inspection procedure.
Malt intended for use in beer brewing or elsewhere in the food industry.
Visual examination of malt for foreign objects. Refer to the Sieving Test for Malt (R-200.08.011).
Desired condition: free of foreign material, stems and leaves
Points to be awarded: 1−5
Whole hops intended for use in beer brewing or elsewhere in the food industry
Evaluation of the harvested hops through visual inspection is employed in order to determine whether a portion may be deemed undesirable . This is aided by gravimetric determination of impurities as well as leaf and stem content.
Consideration of phosphates and impurities, especially hydrolysis products of proteins in the concentration determination of alkaline cleaners on sodium hydroxide (NaOH) and soda (Na2CO3).
All alkaline cleaning solutions or "batch solutions" that contain soda (Na2CO3) as a cleaning component in addition to sodium hydroxide (NaOH).
Additives containing phosphoric acid in particular - but also other types of additive - can simulate a more or less significant Na2CO3 content due to their buffering effect. Firstly, phosphoric acid significantly blunts the p-value by forming sodium phosphate (Na3PO4) and secondly, the difference between the m-value and the p-value is increased because sodium dihydrogen phosphate (NaH2PO4) is largely formed from disodium hydrogen phosphate (Na2HPO4) in the pH range 8.2 to 4.3. The same applies - but to a lesser extent due to the molecular sizes - to typical phosphonic acids or their salts, but not, for example, to most surfactants.
To determine the exact concentration or pH value, the content of buffering substances - phosphates and impurities - must be taken into account in addition to the degree of carbonation, as otherwise the concentration of the active cleaning agent will be too high.
Determination of the p-value of the detergent solution with an acid solution (HCl or H2SO4) with corresponding normality up to the color change of phenolphthalein (pH 8.2).
NaOH + HCl → NaCl + H2O colorless against phenolphthalein
2 NaOH + H2SO4 → Na2SO4 + 2 H2O
Determination of the soda ash (Na2CO3) content of the detergent solution with an acid solution (HCl or H2SO4) with corresponding normality up to the color change from methyl orange (pH 4.3).
Na2CO3 + HCl → NaHCO3 + NaCl
NaHCO3 + HCl → NaCl + H2O + CO2 yellowish brown against methyl orange
2 Na2CO3 + H2SO4 → 2 NaHCO3 + Na2SO4
2 NaHCO3 + H2SO4 → 2 Na2SO4 + H2O + 2 CO2
The most important step is the expulsion of CO2. This is to ensure that no more hydrogen carbonates or carbonates can form during the subsequent back titration with NaOH. For this purpose, a significant acidification below pH 4.3 must be carried out with acid in order to be able to drive out CO2 using an inert gas.
The proportion of buffering substances can then be determined by back titration with NaOH to pH 4.3 or 8.2.