Oxygen can oxidatively polymerize alpha acid, losing its original taste and antiseptic ability. The 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 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, but sometimes the oxidized hops will have a relatively obvious ester aroma. In order to isolate oxygen, vacuum or nitrogen-filled packaging is often used
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.
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.
At present, the hops that can be purchased in large quantities are usually packed in 5kg/bag, and the domestic ready-made equipment is difficult to use up in a short time. Therefore, it is recommended to divide the hops into N small packages immediately after receiving them, and take one bag each time. Can. You can use an aluminum foil bag to evacuate, or you can use an aluminum foil bag to fill with nitrogen or carbon dioxide. Inflation can be used to push out the air in the package and then seal it.
Can be added in small amounts at the end of the boil as a fragrance in wheat brews.
The picture below shows the oxidation effect of limited air in the conical flask on hops, 180d. The left side shows the appearance after oxidation, which is pale yellow, and the right cross section shows the interior of the unoxidized particles, which still retains a small amount of green.
The recommended storage temperature for hops is that the upper limit is not higher than 4°C. Above this temperature, alpha acid begins to attenuate significantly, and polymerizes to form gamma resin, which produces a bitter taste and affects the quality of hops; 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 of 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 will become scattered and oxidized very quickly after contacting the air. Therefore, the recommended storage temperature is between 0-2°C.
It is recommended that the low temperature maniac divide the hops into small packages to avoid the particles in the big bag from breaking and oxidizing when the hops are taken.
Other: Damage to imported hops caused by high temperature generally occurs during transportation. The transportation of hops from abroad to China is all through the cold chain, which basically has no effect. Delivery by express or Debon, the timeliness will be guaranteed. However, in summer and autumn, the country is generally high in temperature, and it takes 2-3 days for express delivery, which will have a significant impact on hops. Therefore, it is best to choose spring and winter for purchasing hops.
Lighting will make the color of the hops turn gray and white, and the aroma components will be lost in large quantities. Therefore, all hops are currently packed in aluminum foil bags.
Hop storage environment, the relative humidity should not be higher than 60%. Excessive humidity can cause:
1. Alpha acid is polymerized to form gamma resin, resulting in post-bitter taste;
2. Moldy bacteria, hops can kill most gram-positive bacteria, and have almost no killing effect on gram-negative bacteria and fungi;
3, rot, plant tissue in an environment with sufficient water, rot is inevitable.