Lesson 2 - Hop Biology and Cultivation

Instead, they are harvested in the midst of their growth, when their moisture content is between 75-80% and their lupulin glands are filled with resins. They should be harvested within 10 days of ripening, to prevent over-ripe cones from shattering.

Historically, hop growing was extremely labour intensive, but harvesting has now become almost fully automated. The process is as follows:

• The hop bines are cut just above the ground, pulled off the support structure, and transported to the harvest centre.
• The bines are then fed upside down into the hop picker, where the machine separates the cones from the bines (and some leaf and stem material).
• Next fans, screens and inclined conveyor belts are used to separate the leaf and stem material from the cones.
• The separated bines are chopped into mulch and composted. The compost is spread over the hop growing area.
• The hop cones are then dried in a hop kiln using warm air, at a temperature of 65^°C. This reduces cone moisture from 80% to 10%. This helps to prevent the hop cones from deteriorating e.g. changing colour, developing a poor odour, or becoming mouldy.
• Next, the hops are conditioned. In conditioning the moisture level is evened out within the cones and throughout the batch. The hops are kept in a chamber at 20-24°C, with a relative humidity of 58-65%. If hop cones are not dried to 12% or below and cooled, the bales can combust!
• Finally, the hops are compressed and baled to reduce storage requirements and costs.