# Hop Freshness

The Hop Freshness calculator estimates alpha acid degradation over time based on storage conditions.

## How to Use

1. **Select Hop Variety** - Choose from database or enter custom
2. **Enter Storage Details** - Temperature, packaging date, package type
3. **Select Packaging Type** - Nitrogen Flushed (Pro), Inert-gas Flush, Vacuum Sealed, Wrapped, or Loose
4. **Input Original Alpha Acids** - Listed on package
5. **Input Beta Acid %** - Listed on package
6. **Input Loss After 6 Months %** - Percentage of alpha acid lost after 6 months of storage
7. **Input Storage Duration in Months** - How long the hops have been stored
8. **View Results** - Alpha Acid %, Beta Acid %, Percent Lost %, Freshness Factor, Oxidized Alpha Acid %, Oxidized Beta Acid %, Hop Storage Index

## About Hop Degradation

Hops lose their alpha acids over time through oxidation. The rate of degradation depends on:

* **Storage temperature**: Colder is better
* **Packaging type**: Vacuum sealed, nitrogen flushed
* **Hop variety**: Some varieties store better
* **Time since harvest**: Fresher hops last longer
* **Exposure to oxygen**: Minimized in proper packaging

## Storage Guidelines

### Temperature Effects

* **Freezer (-20°C / 0°F)**: 5-10% loss per year
* **Refrigerator (4°C / 40°F)**: 15-20% loss per year
* **Cool Room (15°C / 60°F)**: 30-40% loss per year
* **Room Temp (20°C / 70°F)**: 50%+ loss per year

### Packaging Impact

* **Nitrogen Flushed (Pro)**: Best preservation
* **Inert-gas Flush**: Very good preservation
* **Vacuum Sealed**: Good preservation
* **Wrapped**: Moderate preservation
* **Loose**: Rapid degradation

## Hop Storage Index (HSI)

Different hop varieties have different storage stability:

* **<30% HSI**: Poor storage (Noble hops)
* **30-40% HSI**: Moderate storage
* **40-50% HSI**: Good storage
* **>50% HSI**: Excellent storage

### Examples by Variety

* **Cascade**: \~48% HSI (good)
* **Centennial**: \~45% HSI (good)
* **Saaz**: \~25% HSI (poor)
* **Fuggle**: \~30% HSI (moderate)

## Storage Tips

* Keep hops frozen for best preservation
* Vacuum seal opened packages
* Store in dark conditions
* Use oldest hops first (FIFO)

## Calculating Adjustments

### Example Calculation

* Original: 10% AA Cascade
* Storage: 6 months at 4°C (40°F)
* Estimated loss: 10%
* Current AA: 9%
* Adjustment: Use 11% more hops

## Advanced Mode

The Hop Freshness calculator also includes an Advanced Mode that provides additional inputs and outputs for more detailed analysis:

### Advanced Inputs

* **Beta Acid** — The beta acid percentage of the hops
* **Decay Rate Constant k** — The rate constant for alpha acid degradation
* **Hop Storage Index** — A measure of the hop's storage stability

### Advanced Results

In addition to the standard results, Advanced Mode displays:

* **Oxidized Alpha Acid %** — The percentage of alpha acids that have oxidized
* **Oxidized Beta Acid %** — The percentage of beta acids that have oxidized
* **Hop Storage Index** — Calculated storage stability index

## Using with Your Brewing

* Calculate adjusted AA% for recipe planning
* Track your hop inventory freshness
* Adjust quantities to maintain target IBUs
* The tool remembers your last entered values

## Related docs

* [Recipe Designer](/recipes/designer.md)
* [Brewing Knowledge: Boil and Hopping](/brewing-knowledge/boil-and-hopping.md)


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