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.
Analysis for determining the taurine content after derivatization using HPLC
This analysis is suitable for energy drinks and NAB.
Taurine is derivatized using dansyl chloride, separated using HPLC in reversed phases and determined with a fluorescence detector.
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.
Determination of caffeine and theobromine using HPLC
This method is suitable for beverages containing caffeine, tea-based beverages and NAB.
Caffeine and theobromine are separated using HPLC and reversed phases and determined by means of UV detection.
Determination of glucuronolactone by means of ion chromatography and pulsed amperometric detector
This method is suitable for energy drinks and non-alcoholic beverages.
Glucuronolactone is separated by means of a strongly alkaline eluent with an ion exchange column. It is detected and quantified electrochemically using a pulsed amperometric detector (PAD).
Through creating a potential, the ions are oxidized on a gold electrode and induce a measurable charge. To prevent the electrode from being coated over a short time, the potential is then reversed to reduce and release the ions from the electrode.