Hop Preservation in Craft Beer
The most commonly used hop forms in craft beer include Pellet and Leaf Hop, which have similar preservation requirements. Hop preservation must address five issues: oxygen, temperature, light, humidity, and biology.
1. Oxygen
Oxygen can oxidatively polymerize alpha acid, losing its original taste and antiseptic ability. Polymerized hard resin, such as gamma resin, is one of the main sources of bitterness after hops. The oxidation of high molecular polyphenols in hop polyphenols will give the beer a rough, bitter taste. The oxidation of the aroma substances in the hops will lead to the disappearance or change of the aroma characteristics of the hops. Still, sometimes the oxidized hops will have a relatively obvious ester aroma. To isolate oxygen, vacuum or nitrogen-filled packaging is often used.
Vacuum packaging:
Hop particles, especially those with high oil content, will be compacted into a whole, which is very strong, not easy to break, inconvenient to use, and not very useful. At present, this kind of packaging has become less and less.
Nitrogen-filled packaging:
There is a large amount of nitrogen in the aluminum foil bag, and there is no adhesion between the hop particles, which is convenient to use and is currently the most widely used packaging form.
Brewhouse preservation method:
At present, the hops that can be purchased in large quantities are usually packed in 5kg/bag, and the ready-made domestic equipment takes time to use quickly. Therefore, it is recommended to divide the hops into N small packages immediately after receiving them and take one bag each time. You can use an aluminum foil bag to evacuate or an aluminum foil bag to fill with nitrogen or carbon dioxide. Inflation can be used to push out the package’s air and seal it.
Oxidized Hops:
Can be added in small amounts at the end of the boil as a fragrance in wheat brews.
2. Temperature
The recommended storage temperature for hops is that the upper limit is not above 4°C. Above this temperature, alpha acid begins to attenuate significantly and polymerizes to form gamma resin, producing a bitter taste and affecting hop quality; the lower limit is not required. Low temperature is conducive to maintaining the original quality of hops.
When the temperature is below 0 °C, the shelf life can be up to five years. The disadvantage of freezing far below 0°C is the change in hop morphology. The hop particles themselves contain about 8% moisture. The moisture freezes at the freezing point, and the volume expands. Once the temperature returns to normal, the particles become scattered and oxidize quickly after contacting the air. Therefore, the recommended storage temperature is between 0-2°C.
The low-temperature maniac is recommended to divide the hops into small packages to prevent the particles in the big bag from breaking and oxidizing when the hops are taken.
3. Lighting
Lighting will make the hops color gray and white, and the aroma components will be lost in large quantities. Therefore, all hops are currently packed in aluminum foil bags.
4. Humidity
Hop storage environment, the relative humidity should not exceed 60%. Excessive humidity can cause:
Alpha acid is polymerized to form gamma resin, resulting in a post-bitter taste;
Moldy bacteria, hops can kill most gram-positive bacteria and have almost no killing effect on gram-negative bacteria and fungi;
Rot, plant tissue in an environment with sufficient water, rot is inevitable.
