Determination of the correct Velcorin® dosage.
flavored beverages, liquid tea concentrate, fruit wine, non-alcoholic wine
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.
A known quantity of an internal standard (n-propanol) is added to the sample, if necessary after dilution.
The sample is equilibrated at a certain temperature in a headspace vial and part of the headspace is injected into a gas chromatograph.
The ethanol contained is separated on a polar gas chromatography column and detected with a flame ionization detector (FID).
The ethanol concentration in % vol. is calculated from the ratio of the area of the ethanol peak to the area of the internal standard (n-propanol) with the ratios of the same peaks determined when analyzing standards with known ethanol concentrations.
Determination of the original gravity, alcohol and extract content using an oscillating U-tube density measuring device and an alcohol sensor in beer or beer-based beverages
Aside from the density, the alcohol concentration is also directly measured with an alcohol sensor. This is carried out using catalytic combustion. In a measured stream of air, alcohol vapor rises countercurrent to the beer flowing downwards. The alcohol vapor is oxidized at the sensor and the resultant heat is measured by means of a resistive circuit. This correlates with the concentration of alcohol in the beer. According to Tabarié’s equation, the relationship between the specific gravity of beer, its alcohol content and real extract content can be calculated as follows:
\(\rho_{\text{beer}} = \rho_{\text{alcohol}} \space + \space \rho_{E_R} \space – \space \rho_{\text{water}}\)
\(\text{SG}_{\text{A20/20 beer}} = \text{SG}_{\text{A20/20 alcohol}} \space + \space \text{SG}_{\text{A20/20}}E_R \space – \space \text{SG}_{\text{A20/20 water}}\)
\(\text{SG}_{\text{A20/20 alcohol}} = 1.000\)
The method is suitable for beer brewed to any original gravity or to any alcohol content.
Volatile compounds in beer are concentrated through distillation and extracted with dichloromethane. The solvent phase is analyzed with a gas chromatograph. The linearity of the detector and the determination of the concentrations of analytes in the sample are achieved by using multiple concentration levels within the relevant range and through evaluation of the relative area under the peaks.
Determination of copper content in beer
This method is also suitable for dark and turbid beers. The turbidity particles must be evenly distributed before sampling.
This method is based on the formation of a yellowish-brown, (insoluble in aqueous medium) copper (II) chelate with zinc benzyl dithiocarbamate (ZDBT), a compound that may be extracted with trichloroethane.
Determination of ethanol by enzymatic methode (only alcohol dehydrogenase) for samples with low ethanol content.
Suitable for beers, non-alcoholic beers, reduced-alcohol beers, beer-based drinks, NAB, juice, beverages.
Ethanol is oxidized by nicotinamide adenine dinucleotide (NAD) in the presence of the enzyme alcohol dehydrogenase (ADH) to acetaldehyde:
\(\text{Ethanol + NAD}^+ \space ^{\underrightarrow{\text{ADH}}} \space \text{Acetaldehyd + NADH + H}^+\)
The equilibrium of this reaction favors the side with ethanol and NAD. In an alkaline medium, the equilibrium can be shifted to favor the substances on the right side of the equation.
The amount of NADH+H+ produced in the reaction is equivalent to the amount of ethanol and is measured photometrically due to its absorption at wavelengths of 340 nm.
Specificity of the determination [1]
The influence of aldehydes and ketones is eliminated by the order of reagent addition during the test. Methanol is not converted due to unfavorable KM values (Michaelis-Menten constant) of the enzymes used.
n-propanol and n-butanol are quantitatively converted under test conditions, higher primary alcohols lead to sample-dependent creep reactions. Secondary, tertiary and aromatic alcohols do not react. Glycerin does not interfere with the test even at higher concentrations.
Acetaldehyde does not interfere below a concentration of 3000 mg/l. Sulphite does not interfere below a concentration of 300 mg/l.