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The inner lining of the mini keg and the lid should not influence the aroma or flavor of the product in any way. For this reason, the inner lining must conform to the regulations governing foods in the European Union and to those of the respective member states pursuant to their valid constitutions. Furthermore, the provisions drawn up by the BGVV Commission on Plastics in Germany (Bundesinstitut für gesundheitlichen Verbraucherschutz und Veterinärmedizin) must also be taken into consideration.

The safest approach is to perform a comparative taste test with water or beer from the same batch that has been treated in an identical manner in a mini keg (sample) and in a bottle (reference). 

Glucose and fructose are phosphorylated by the enzyme hexokinase (HK) and adenosine 5'-triphosphate (ATP) to glucose 6-phosphate (G-6-P) and fructose 6-phosphate (F-6-P):

\(\text{Glucose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{G-6-P + ADP}\)

\(\text{Fructose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{F-6-P + ADP}\)

In the presence of the enzyme glucose-6-phosphate dehydrogenase (G6P-DH), G-6-P is oxidized from nicotinamide adenine dinucleotide phosphate (NADP⁺) to gluconate-6-phosphate. Reduced nicotinamide adenine dinucleotide phosphate (NADP + H⁺) is formed:

\(\text{G-6-P + NADP}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-phosphate + NADP + H}^+\)

The amount of NADP + H⁺ formed during the reaction is equivalent to the amount of glucose. NADP + H⁺ is a measurand and is determined based on its absorbance at 340 nm.

After the reaction is complete, F-6-P is converted to G-6-P by phosphoglucose isomerase (PGI):

\(\text{F-6-P} \space ^{\underrightarrow{\text{PGI}}} \space \text{G-6-P}\)

G-6-P reacts in turn with NADP⁺ to form gluconate-6-phosphate and NADP + H⁺. The additional amount of NADP + H⁺ formed is equivalent to the amount of fructose and is determined photometrically based on its absorption at 340 nm.

Note:

Alternatively, NAD⁺/NAD + H⁺ can be used instead of NADP⁺/NADP + H⁺:

\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)

Determine the SG_A20/20 obtained from pycnometry or the density measured with a precision hydrometer or another device for measuring the density. Using the value from the SG_A20/20 measurement or the density from the sugar, alcohol, original gravity and correction table according to GOLDINER/KLEMANN, BLOCK, KÄMPF or a polynomial, determine the apparent extract content of the sample.

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⁺:

\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)

The D-glucose content is determined before and after enzymatic hydrolysis of sucrose. D-fructose is measured following D-glucose determination.

D-glucose/D-fructose determination before inversion:

Glucose and fructose are phosphorylated by the enzyme hexokinase (HK) and adenosine-5'-triphosphate (ATP) to glucose-6-phosphate (G-6-P):

\(\text{Glucose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{G-6-P + ADP}\)

\(\text{Fructose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{F-6-P + ADP}\)

In the presence of the enzyme glucose-6-phosphate dehydrogenase (G6P-DH), G-6-P is oxidized from nicotinamide adenine dinucleotide phosphate (NADP⁺) to gluconate-6-phosphate. Reduced nicotinamide adenine dinucleotide phosphate (NADP + H⁺) is formed:

\(\text{G-6-P + NADP}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-phosphate + NADP + H}^+\)

The amount of NADP + H⁺ formed during the reaction is equivalent to the amount of glucose. NADP + H⁺ is measurand and is determined based on its absorbance at 340 nm.

After the reaction is complete, F-6-P is converted to G-6-P by phosphoglucose isomerase (PGI):

\(\text{F-6-P} \space ^{\underrightarrow{\text{PGI}}} \space \text{G-6-P}\)

G-6-P reacts in turn with NADP⁺ to form gluconate-6-phosphate and NADP + H⁺. The additional amount of NADP + H⁺ formed is equivalent to the amount of fructose and is determined photometrically based on its absorbance at 340 nm.

Enzymatic inversion:

Sucrose is hydrolyzed to glucose and fructose by the enzyme β-fructosidase (invertase) at pH 4.6:

\(\text{Saccharose + H}{_2}\text{O} \space ^{\underrightarrow{\text{β-Fructosidase}}} \space \text{Glucose + Fructose}\)

The D-glucose determination after inversion (total D-glucose) is carried out as described above.

The sucrose content is calculated from the difference between the glucose concentration before and after enzymatic inversion.

Sucrose is important as a fermentable sugar for the technology of wort and beer production. Sucrose also plays a role in the evaluation and assessment of malt beverages and nutritional beers.

D-glucose content is determined before and after enzymatic hydrolysis of sucrose.

Sucrose is hydrolyzed by the enzyme β-fructosidase (invertase) at pH 4.6 to glucose and fructose:

\(\text{Sucrose + } H_2O \space {\xrightarrow{β-fructosidase}} \space \text{D-glucose + D-fructose}\)

Glucose is phosphorylated by the enzyme hexokinase (HK) and adenosine 5'-triphosphate (ATP) to glucose 6-phosphate (G-6-P):

\(\text{Glucose}+\text{ATP} \space \xrightarrow{HK} \space \text{G-6-P + ADP}\)

In the presence of the enzyme glucose-6-phosphate dehydrogenase (G6P-DH), G-6-P is oxidized from nicotinamide adenine dinucleotide phosphate (NADP) to gluconate-6-phosphate. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is formed:

\(\text{G-6-P + NADP} \hspace{0.8em} \xrightarrow{G6P-DH} \hspace{0.8em} \text{gluconate-6-phosphate + NADP + H}^+\)

The amount of NADPH formed during the reaction is equivalent to the amount of glucose. NADPH is a measurand and is determined on the basis of its absorbance at 334, 340 or 365 nm.

The sucrose content is calculated from the difference between the glucose concentration before and after enzymatic inversion.