What are two factors that can influence the estimation of IBU in beer?

The estimation of International Bitterness Units (IBU) in beer is significantly influenced by the form of hops used and the boil time during brewing.

The form of hops, such as whole leaf, pellets, or extracts, affects how efficiently the alpha acids in the hops are isomerized during the boiling process, which directly impacts the bitterness levels in the finished beer. Different hop forms may yield varying levels of bitterness due to the differences in surface area and essential oil content, affecting solubility and extraction.

Boil time is also critical in determining IBU. The longer the hops are boiled, the more alpha acids are isomerized, leading to a higher IBU. Typically, hops added later in the boil contribute less bitterness because they have less time to isomerize, whereas hops added at the beginning of the boil contribute more significantly to the bitterness due to the extended exposure to heat.

In contrast, while yeast type and fermentation temperature can influence flavor and aroma profiles, they do not have a direct role in determining IBU levels. Factors like water pH can affect hop extraction and solubility, but they are not as directly correlated to IBU measurement as the method of hopping and boil duration. Similarly, carbonation level and storage conditions