In the detection of α - acids in hops, the commonly used international standard methods mainly include the methods of the European Brewery Convention (EBC), the American Society of Brewing Chemists (ASBC), etc. The detailed introductions are as follows:
The EBC 7.5 standard specifies the method for determining the α - acid content in hops and their products, which is applicable to various types of hops and related products.
Based on spectrophotometry. The α - acids in hops form a specific complex in an alkaline potassium iodide solution. This complex has a characteristic absorption peak at a wavelength of 325 nm. The α - acid content is determined by measuring the absorbance and comparing it with the standard curve.
Sample Preparation
Extraction
Add a mixed extraction agent of isooctane - methanol, and shake for extraction for a certain period (such as 30 minutes) to allow the α - acids to dissolve fully into the solvent. Then transfer the solution to a separating funnel, add an appropriate amount of water for washing, and separate the organic phase.
Color Development
Take a certain volume of the organic phase, add an alkaline potassium iodide solution, and react in the dark for a certain period (such as 10 minutes) to allow the α - acids to react fully with the reagent to form a colored complex.
Absorbance Measurement
Measure the absorbance of the colored solution at a wavelength of 325 nm using a spectrophotometer. At the same time, prepare a series of α - acid standard solutions with known concentrations, operate and measure the absorbance according to the same steps, and plot a standard curve.
Result Calculation
According to the absorbance of the sample solution, find the corresponding α - acid concentration from the standard curve, and then calculate the α - acid content in the sample by combining parameters such as the sample weight and the volume of the constant - volume solution.
The ASBC method is widely used in North America for the detection of α - acids in hops and related products, and is applicable to various hop samples.
Also based on spectrophotometry, through specific chemical treatments, the α - acids exhibit absorbance characteristics at specific wavelengths, and then their content is determined.
Sample Treatment
Extraction Process
Add a mixed solvent of isooctane - methanol, shake for extraction for a certain period (such as 15 - 30 minutes), then transfer the solution to a separating funnel, wash with water, separate the organic phase, transfer the organic phase to a volumetric flask, and make up to volume.
Color Reaction
Take a certain amount of the made - up solution, add a specific color - developing agent (such as alkaline potassium iodide), and react under suitable conditions (such as at room temperature and in the dark for 5 - 10 minutes).
Absorbance Determination
Measure the absorbance of the colored solution at a wavelength of 325 nm using a spectrophotometer. At the same time, prepare a series of α - acid standard solutions, operate and measure the absorbance according to the same process, and plot a standard curve.
Content Calculation
Although there is currently no unified international HPLC standard specifically for the detection of α - acids in hops like EBC and ASBC, HPLC is increasingly used in scientific research and high - end detection due to its advantages of good separation effect and high accuracy. Its operation generally includes:
Sample Pretreatment
Accurately weigh the hop sample, extract it ultrasonically with a suitable solvent (such as a methanol - water mixture), centrifuge, take the supernatant, and filter it through a membrane to remove impurities.
HPLC Analysis
Select a suitable chromatographic column (such as a C18 reverse - phase column), prepare a specific mobile phase (composed of water, organic solvents, and acids, etc.), inject the treated sample into the HPLC system, and separate the α - acids under specific conditions.
Detect the α - acids through an ultraviolet detector (usually with a detection wavelength of 314 nm). At the same time, inject standards to plot a standard curve, and finally calculate the α - acid content according to the peak area or peak height of the sample.
TAG：
Hot News 
Contact Us 
