Search: mixed varieties

This test detects the presence of most varieties of two-rowed and multi-rowed winter barley possessing a green aleurone layer. This test is based upon the reaction between HCl and the green pigment, which turns red in its presence.

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:

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

The amount of NADPH+H⁺ formed during the reaction is equivalent to the amount of glucose. NADPH+H⁺ is determined based upon its absorbance at 340 nm.

Note:

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

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

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:

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

The amount of NADP + H⁺ formed during the reaction is equivalent to the amount of glucose. NADPH + 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):

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

The amount of NADPH + H⁺ formed during the reaction is equivalent to the amount of fructose. NADPH + H⁺ is the parameter being measured and is determined on the basis of its absorption at 340 nm.

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⁺/NADPH + 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.

The beer-based beverage segment includes beverages with a wide variety of compositions.

Both clear and yeasty beers are used in the mix. The proportion of beer varies between 30 and 90 %. Clear or fruit-flavoured soft drinks are used. Various sweetening components are also used. The pH value of the finished beverage can vary greatly from product to product. These diverse influencing factors have an affect on the microflora, which can negatively impact the respective product.

Table 1 provides an overview of the harmfulness of microorganisms in mixed-beer beverages.

In addition to OFS agar and SSL broth, other culture media can be used as an alternative.