Hops and hop products intended for use in beer brewing or elsewhere in the food industry
Hop constituents are distributed between an aqueous acidic methanolic phase and diethyl ether. Hop bitter substances extracted with ether are subsequently separated according to their different solubility properties in cold methanol and hexane into fractions: total resins, soft resins and hard resins. The soft resins are further separated according to their capacity to form complexes with lead salts into α-acids (conductometer value) and a β-fraction.
Hop extract intended for use in beer brewing or elsewhere in the food industry
Determination of glucose and fructose by enzymatic means.
Suitable for beers, mixed beer beverages, malt beverages, non-alcoholic soft drinks, NAB, juices and drinks.
Glucose is phosphorylated by the enzyme hexokinase (HK) and adenosine 5'-triphosphate (ATP) to glucose 6-phosphate (G-6-P).
\(\text{Glucose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{G-6-P + ADP}\)
In the presence of the enzyme glucose-6-phosphate dehydrogenase (G6P-DH), G-6-P is oxidized by nicotinamide adenine dinucleotide phosphate (NADP+) to gluconate-6-phosphate. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is formed:
\(\text{G-6-P + NADP}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{gluconate-6-phosphate + NADP + H}^+\)
The amount of NADPH formed during the reaction is equivalent to the amount of glucose. NADPH is determined based upon its absorbance at 340 nm.
Note:
Alternatively, NAD+/NAD + H+ can be used instead of NADP+/NADP + H+:
\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)
This method describes how to determine the hard resin fraction in hops and hop products; for the procedure, refer to the MEBAK method R-300.03.901 [2016-03].
Hops and hop products intended for use in beer brewing or elsewhere in the food industry
The hard resins are calculated by subtracting the soft resins from the total resins. This yields the hard resin content as a percentage of the total resins.
Determination of the total air in bottles and cans
Determination of the total air in containers for beer, beer-based beverages and carbonated beverages
Through heating and shaking, the gases contained in beer are collected in a burette filled with potassium hydroxide. The carbon dioxide is bound by potassium hydroxide, and the remaining volume of gas, consisting of oxygen and nitrogen, is measured [1].
This method describes how to determine the quantity of lime water necessary for softening water used in brewing (brewing liquor) and food production.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
Through the addition of lime water or 'milk of lime,' the hydrogen carbonates and free carbon dioxide are transformed into carbonates and are then largely precipitated:
Ca(HCO3)2 + Ca(OH)2 → 2 CaCO3 + 2 H2O
Mg(HCO3)2 + Ca(OH)2 → MgCO3 + CaCO3 + 2 H2O
CO2 + Ca(OH)2 → CaCO3 + H2O
Calcium carbonate is insoluble and precipitates out. By contrast, magnesium carbonate is to a large extent soluble in water. The addition of one more equivalent weight of Ca(OH)2 transforms magnesium carbonate into insoluble magnesium hydroxide:
MgCO3 + Ca(OH)2 → CaCO3 + Mg(OH)2
However, the amount calculated for this form of water treatment would lead to a surplus of lime in the water (and a higher than desired pH), since an especially high alkalinity is required for the quantitative precipitation of magnesium hydroxide. Therefore, the “split treatment” method, as it is known, is preferred, i.e., the quantity of lime water calculated for the total quantity is added to ⅔ of the untreated water. An excess of lime results, and therefore, the magnesium hydrogen carbonate is also precipitated. The addition of approx. ⅓ of the untreated water diminishes the lime surplus and causes the complete precipitation of calcium hydrogen carbonate. By doing so, the hardness caused by calcium carbonate is entirely eliminated, and the hardness caused by magnesium carbonate is to a large extent as well.