Calculating IBU (International Bitterness Units) in brewing is a crucial step to determine the bitterness of a beer. As a sommelier and brewer, I have had the opportunity to delve into this process and understand the methods used to measure IBUs. In the brewing laboratory, two commonly employed techniques are the UV light spectrophotometric assay and high-pressure liquid chromatography (HPLC) methods. Let's explore these methods in detail.
1. UV Light Spectrophotometric Assay:
The UV method is widely used, even in small brewery laboratories, due to its simplicity and cost-effectiveness. It involves measuring the absorbance of light at a specific wavelength by the bittering compounds in the beer sample. The higher the absorbance, the higher the concentration of bitter compounds, and therefore, the higher the IBU.
Here's a simplified step-by-step process of the UV method:
– A sample of the beer is taken and diluted with a suitable solvent.
– The diluted sample is then passed through a spectrophotometer.
– The spectrophotometer emits UV light at a specific wavelength, usually around 275-350 nm.
– The light passes through the sample, and the amount absorbed is measured.
– The absorbance value is then converted into IBU using a calibration curve obtained from standards of known bitterness.
Personally, I have performed this method in the lab, and it requires careful handling of the samples and precise calibration of the instrument. It's fascinating to see how the absorption of light can be correlated with the bitterness of the beer.
2. High-Pressure Liquid Chromatography (HPLC):
HPLC is a more advanced and accurate method for measuring IBU. It involves separating and quantifying individual bitter compounds present in the beer using a high-pressure liquid chromatograph. This method provides a detailed analysis of the bittering components, allowing for a more precise determination of IBU.
Here's a breakdown of the HPLC method:
– A beer sample is prepared by diluting it with a suitable solvent.
– The sample is injected into the HPLC system, which consists of a column, mobile phase, and detector.
– The bitter compounds in the sample are separated based on their chemical properties as they pass through the column.
– The separated compounds are then detected by a UV detector or a refractive index detector, and their concentration is measured.
– The concentration values are used to calculate the IBU based on the specific bitter compounds analyzed.
While I haven't personally performed HPLC analysis for IBU determination, I have discussed this method with experienced brewers. They appreciate its ability to provide a comprehensive breakdown of the different bitter compounds, offering valuable insights into the beer's bitterness profile.
IBUs are calculated using either the UV light spectrophotometric assay or high-pressure liquid chromatography (HPLC) methods in a brewing laboratory. The UV method is commonly used in small breweries due to its simplicity and cost-effectiveness, while HPLC provides a more precise analysis of individual bitter compounds. Both methods contribute to understanding and quantifying the bitterness of beer, enhancing the overall brewing process and ensuring consistent quality. As a sommelier and brewer, I find the IBU calculation process intriguing and crucial in creating balanced and enjoyable beer experiences.