How quickly do hops lose alpha acid?

The rate depends heavily on storage. Vacuum-sealed hops in a freezer lose about 0.5% of their alpha acid per 6 months. In a fridge, losses are about 1.5% per 6 months. At room temperature, losses can be 4%+ per 6 months.

What is the Hop Storage Index (HSI)?

HSI measures how quickly a hop variety degrades. High-alpha hops (like Magnum or Columbus) tend to have lower HSI values and store better. Low-alpha aroma hops (like Saaz or Hallertau) degrade faster. Check supplier data for specific HSI values.

Are old hops still usable?

Hops that have been properly stored (vacuum sealed, frozen) are usable for 2-3 years with reasonable alpha acid adjustment. Hops that smell cheesy, musty or unpleasant should be discarded. Aged hops can also be intentionally used in lambic-style beers.

How should I store hops for maximum freshness?

Vacuum seal hops immediately after opening and store in a freezer. Exposure to oxygen, light and heat are the main causes of degradation. Nitrogen-flushed packaging from suppliers is ideal. Never store open hop bags at room temperature.

Do pellets or whole hops store better?

Pellet hops generally store slightly better than whole/leaf hops because they have less surface area exposed to oxygen. The processing also ruptures lupulin glands, but the compressed form limits further oxidation. Both types should be vacuum sealed and frozen.

BrewCalcs

Hop Freshness Calculator — Alpha Acid Degradation

Estimate remaining alpha acid potency based on hop age and storage conditions.

Original Alpha Acid

AA% when purchased

Age

Your age in years

Storage Conditions

Check supplier data for variety-specific HSI values

How We Calculate This

Alpha Acid Degradation

Alpha acids degrade over time through oxidation. The rate depends on temperature, oxygen exposure, and the hop variety's inherent storage stability (HSI). This calculator uses simplified decay rates based on typical storage conditions.

Remaining AA = Original AA x (1 - decay rate)^(months/6)

Frequently Asked Questions

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Last updated: 2025-02-20

All calculations are estimates. Always verify values and adjust based on your equipment and ingredients.