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DMDC (Velcorin®) is used for the cold sterilization of non-alcoholic beverages.

According to the EU guideline EG 1129/2011 [1], up to 250 mg/l DMDC may be added to flavored non-alcoholic beverages, non-alcoholic wine and liquid tea concentrates.

Dimethyl dicarbonate (Velcorin®) quickly dissociates in aqueous solutions almost completely to carbon dioxide and methanol. In addition, small amounts of ethyl methyl carbonate are formed through the reaction of DMDC with ethanol, which can be detected through GC-MS analysis techniques [2]. The amount of DMDC added to a beverage can be determined by measuring the content of EMC and ethanol. The Velcorin® dosage can be checked by measuring the amount of methanol quantitatively using GC analysis; however, the initial amount of methanol present in the product prior to adding Velcorin® must be determined.

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 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⁺:

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

The pH value influences the enzymatic degradation processes during mashing and determines the solubility of the proteins, the hop bitters and the coloration during wort boiling. Furthermore, there is a dependence between the pH of the wort and that of the beer prepared from it. Beers with high pH values are more susceptible to chemical-physical turbidity due to inadequate protein coagulation in the brewhouse. Measuring the pH of wort and beer is therefore part of routine quality control.

The pH value is determined electrometrically [1-4].

Determination of pH is always done in the same way for wort, beer, beer-based beverages, NAB, juices and beverages.

Carbonated beverages must be decarbonated before measurement.

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.