Alcoline – direct in-line alcohol* measurement system for biotechnology and beverage industry
*) that includes methanol and methane measurement
Measuring alcohol in complex mixtures directly has the advantage to be independent of nomograms which are often not or insufficiently known. Especially for the quality control of new alcoholic party drinks which has to be rapidly introduced into the market the calibration of indirect methods takes too much time.
Traditional density measurement systems are usually not suited to measure alcohol in alcohol-free beers or to detect unwanted alcohol traces in syrups. Alcoline units which are capable of these tasks have been provided by us to yeast and vinegar production lines all over the world for many years.
In a unique way the direct alcohol measurement of the Alcoline system is based on the combination of our standard tubing probe with a specifically selected sensor. The tubing probe separates the volatile components permeating through a double membrane from the liquid mixture. A continuous very constantly flowing carrier gas (synthetic air) is transporting these components from the backside of the membrane to the sensor system which determines selectively the alcohol concentration in the carrier gas. Since there is a linear relation between the permeation rate of alcohol through the membrane and its concentration in the liquid, the alcohol content can be easily determined from the sensor signal. For low alcohol concentration ( < 6 Vol %) a gas sensor yields the most accurate results. For higher alcohol concentrations (2…20 Vol%) infrared sensor systems are applied.
The FMC Mini of the Alcoline system corrects the sensor signals for the temperature and displays the alcohol concentration together with the product temperature. The measurement is initially calibrated at our site with aqueous alcohol solutions. Usually it is re-calibrated with an in-line reference calibration. The measured values are accessible at digital serial and analogue interfaces.
With its controllers, digital and analogue I/O ports the Alcoline System is capable of controlling complete units such as carbonization or blending systems.
All parts of the Alcoline system which are in contact with the product are made of stainless steel or silicon and are free of any microbiological hazards. The probe is cleaned along with any CIP – procedure.
One Mini-FMC can be equipped with two measurement sites. The alcohol probe can be combined with one other probe such as Brix, CO2 or O2.
In combination with a refractometer the Alcoline System does a very accurate and reliable on-line beer analysis even for alcohol-free beer or mixed beer drinks. It does not require a CO2 correction which reduces the costs for complete systems compared to density measurement systems.
Gas sensor (lower alcohol concentration, methanol)
The alcohol vapour permeates through the membrane from where it is transported by means of the carrier gas to the gas sensor. Alcohol molecules are replacing absorbed oxygen molecules at the grain boundaries of the SnO2 ceramic thus reducing its resistivity. From the resistivity change the alcohol concentration can be calculated.
The SnO2 sensor is heated in order to have a rapid regeneration of its surface with oxygen supplied by the carrier gas.
Infrared sensors (upper alcohol concentrations, methane)
Alcohol vapour permeates through the membrane from where it is carried by means of the carrier gas through the IR cuvette. A lamp is providing IR radiation in a broad spectrum. The high selectivity for alcohol is achieved by a interference filters placed in front of the IR double detector.
One filter is tuned to the specific absorption wavelength of ethanol; the other at a slightly different wavelength. The amplifier processes the quotient of both detectors. Thus changes of the lamp intensity with time are eliminated resulting in a drift-free ethanol detection. The processor system is linearly correlating the optical absorption with the concentration of the ethanol in the carrier gas and thus with the ethanol concentration in the product.
Since the alcohol vapour pressure depends exponentially on the temperature, the sensor signal has to be compensated for the temperature.
Applications alcohol measurement
- in-line control of the production of alcohol-free beer
- in-line control fermentation processes for yeast, vinegar, beer and wine
- in-line control of blending systems
- in-line determination of the alcohol amount for tax purposes
- control of alcohol traces in fruit syrups
- in-line beer analysis in combination with a refractometer
- direct measurement of alcohol in mixtures
- continous measurement
- low cross-sensitivity
- robust, easy-to-use