Food (ethanol concentration) detection

This standard specifies the method for determining the alcohol content in alcohol, distilled liquor, fermented liquor, and prepared liquor. This standard is applicable to the determination of alcohol content in alcohol, distilled liquor, fermented liquor, and prepared liquor. Among them, the density bottle method is applicable to distilled spirits, fermented spirits, and blended spirits, the second method is applicable to alcohol and distilled spirits, fermented spirits, and blended spirits (excluding beer), the third method is applicable to wine, fruit wine, and beer, and the fourth method is applicable to digital density meter method for beer, brandy, whiskey, and vodka. The principle of the density bottle method is to remove non volatile substances from the sample by distillation. The density bottle method is used to measure the density of the sample (alcohol aqueous solution) at 20 ° C. Refer to Appendix A to obtain the volume fraction of ethanol content at 20 ° C, which is the alcohol content. The principle of the second alcohol meter method is to remove non volatile substances from the sample by distillation. The alcohol volume fraction is measured using an alcohol meter, and temperature correction is carried out according to Appendix B. The volume fraction of ethanol content at 20 ° C is obtained, which is the alcohol content. The principle of the third method gas chromatography is that when the sample enters the chromatographic column of the gas chromatograph, due to the different adsorption coefficients in the gas solid phases, ethanol is separated from other components. The hydrogen flame ionization detector is used for detection, and compared with the standard sample. Qualitative analysis is conducted based on retention time, and internal standard method is used for quantification. The fourth method is based on the principle of digital densitometer. The sample is injected into a U-shaped tube, and its density is obtained by comparing it with two standard vibration frequencies at 20 ° C. The volume fraction of ethanol content in the sample at 20 ° C is calculated, which is the alcohol content. Instruments and equipment digital density meters. Constant temperature water bath: Temperature control accuracy ± 0.02 ° C. Syringe: 10mL. Analysis Steps: Sample Preparation of Brandy, Whiskey, and Vodka Sample Preparation of Distilled Liquor, Fermented Liquor, and Compounded Liquor Sample Preparation (excluding Beer and Sparkling Wine) Using a clean and dry 100mL volumetric flask, accurately measure 100mL of the sample (liquid temperature 20 ° C) into a 500mL flask, rinse the flask three times with 50mL of water, and merge the washing solution into a 500mL flask. Add a few zeolites (or glass beads) and connect the serpentine condenser tube, Use the original volumetric flask used for sampling as the receiver (with an additional ice bath), turn on the cooling water (the temperature of the cooling water should be below 15 ° C), slowly heat and distill, and collect the distillate. When approaching the mark, remove the volumetric flask, cap it, and keep it warm in a 20 ° water bath for 30 minutes. Then add water to the mark, mix well, and set aside. Preparation of beer samples: Preparation of beer and sparkling wine samples. Carbon dioxide removal is achieved by shaking, ultrasound, or stirring, while ensuring representativeness of the samples without or with minimal loss of alcohol. There are two methods for removing carbon dioxide from the sample: a) Method: Pour approximately 300mL of the wine sample that has been kept at a constant temperature of 15 ° C to 20 ° C into a 1000mL conical flask, add a rubber stopper, and gently shake it in the constant temperature chamber. Open the stopper to release gas (there is a "bang" sound at the beginning), and cover it. Repeat the operation until no gas escapes. Filter with a single layer of medium speed dry filter paper (covered with surface glass on the funnel). b) The second method: Using ultrasonic or magnetic stirring method for degassing, transfer about 300mL of the wine sample with a constant temperature of 15 ° C to a bottle with an exhaust plug, place it in an ultrasonic water tank (or mixer), sonicate (or stir) for a certain time, and filter it with a single layer of medium speed dry filter paper (cover the funnel with surface glass). Note: To determine the ultrasonic (or stirring) time and temperature, it is necessary to compare with the method to ensure that the alcohol content measurement results are similar. After removing carbon dioxide from the sample, it is collected in a conical flask with a stopper, maintained at a temperature of 15 ° C to 20 ° C, sealed for storage, and limited to use within 2 hours. Sample distillation is the same as "preparation of distilled liquor, fermented liquor, and mixed liquor samples". Calibration of instruments (can be carried out according to the instructions of each instrument): Observe and record the "T" value of the air in the U-shaped tube (clean, dry) at (20.00 ± 0.02) ° C. Connect the syringe to the plastic tube at the outlet of the upper end of the U-shaped tube, immerse the plastic tube at the inlet below the U-shaped tube in freshly boiled, cooled, and filtered water before re steaming. Fill the U-shaped tube with water (no bubbles required), and when the water temperature reaches a constant temperature (20.00 ± 0.02) ° C, read and record when the "T" value does not change within 2 minutes to 3 minutes. Device α and β The constant is calculated according to equations (4) and (5): α&Nbsp=&Nbsp; T  2 Water-&Nbsp; T  2 Air (4) β&Nbsp=&Nbsp; T  2 Air (5) In the equation: α&Nbsp; -—— The constant of the instrument calibration process; T  -—— Oscillation period; β&Nbsp; -—— The constant of the instrument calibration process. Convert constant α and β Input the memory unit of the instrument and reset the switch to ρ (Density) level, check the density reading of the water. Pour out the water from the U-shaped tube, dry it, and check the air density. The values should be 1.0000 (density of water) and 0.0000 (density of air), respectively. If the displayed value differs by more than 1 in the 5th decimal place, it is necessary to recheck the temperature of the constant temperature water bath and the "T" values of water and air. The determination of sample solution: Fill the U-shaped tube with the distilled liquid of the sample (without bubbles) until the temperature of the sample solution reaches equilibrium with the water bath temperature (2min~3min), and record the density of the sample. The expression of the analysis results is based on the density measured by the instrument. Refer to Appendix A to obtain the alcohol content of the sample at 20 ° C, expressed in volume fraction% vol. Represented as the arithmetic mean of two independent measurement results obtained under repeatability conditions, with the results rounded to one decimal place. The difference between two independent determination results obtained from precision beer samples under repeatability conditions shall not exceed 0.1% vol; The difference between two independent determination results obtained from other samples under repeatability conditions shall not exceed 0.5% vol

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