Detection of fermentable yeasts and bacteria using a pour plate after prior liquid enrichment.
All cloudy beer-based beverages and lemonades.
The sample, which has been pre-enriched in SSL broth, is suspended in culture medium (OFS agar), incubated and analysed.
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+:
\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)
Detection of harmful yeasts and bacteria by means of membrane filtration and subsequent incubation on OFS agar.
All clear beer-based beverages and lemonades.
The sample is membrane-filtered, incubated and analysed.
The method describes alternative culture media to OFS agar and SSL broth.
All beer-based beverages, lemonades, base products and sugar.
In addition to OFS agar and SSL broth, other culture media can be used as an alternative.
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 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+:
\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)
Determination of glucose, fructose, sucrose by enzymatic means.
Suitable for wort, beer, malt beverages, nutritive beer, beer-based beverages, NAB, juices and beverages
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.