Determination of the total acidity through titration
This method is used to determine the total titratable acids in beverages and concentrates.
Titratable acidity represents the sum of the free acids present in a beverage, with the exception of the dissolved carbon dioxide (carbonic acid). In fruit juices and the beverages prepared from them, they usually consist of malic acid, citric acid and tartaric acid.
The titration of the degassed beverage sample (freed from carbonic acid) is carried out potentiometrically using 0.25 mol/l sodium hydroxide solution either to a pH of 7.0 calculated as tartaric acid or to a pH of 8.1 calculated as citric acid.
This method describes the determination of four hop aroma compounds found in hops and hop products using gas chromatography.
Hops and hop products intended for use in beer brewing or elsewhere in the food industry
The hop oil obtained through steam distillation (refer to links) is dissolved in an organic solvent, separated into its components by means of gas chromatography and determined with a flame ionization detector. The contents are expressed as a percentage of the area of each component compared to the overall area of the peak.
Whole hops intended for use in beer brewing or elsewhere in the food industry
Evaluation of the appearance of hop cones is performed through visual and manual inspection.
Whole hops intended for use in beer brewing or elsewhere in the food industry
Evaluation of the appearance of hop cones is performed through visual inspection and sensory assessment.
Determination of the content of steviol glycosides and stevia products in beverages.
All mixed beer drinks and beverages in general.
The decarbonated and diluted sample is chromatographically separated on a polar-endcapped amino-HILIC phase and detected using a mass spectrometer with ESI source. The quantitative evaluation is carried out by external calibration.
Determination of glucose and fructose by enzymatic means.
Suitable for beer, malt drinks, low-alcohol beer, beer-based mixed drinks, non-alcoholic soft drinks, NAB, fruit juices, soft drinks and other beverages.
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+:
\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)