The Hop-growing Year: The Harvest*
The timing is important
It should be possible to obtain a maximum yield with best quality hops by harvesting the respective variety at the right time and by perfectly picking and drying the hops. The following factors are influenced by the harvest-time:
- content of bitter compounds (% alpha-acids)
- bitter quality (e.g. cohumulone proportion)
- total content of oil (aroma content)
- composition of oil (aroma quality)
- colour and lustre
- infestation by pests and diseases
The right harvest-time Is Important for a high yield and good quality. Hops which are harvested too early are not yet fully mature and therefore produce lower yields. Whereas the content of bitter compounds has soon reached its climax in the case of most of the bitter varieties, if harvested too early in particular the yield is wasted; If they are cut back ahead of time when harvested too early the hops can also react with weaker growth and a lower yield the following year. When harvested too late past the optimum time range then above all the exterior quality and the aroma suffers.
Without technology here nothing would be possible
At the centre of the hop harvest is the stationary picking machine. The hop bines have to be driven with 40 trips per hectare to the stationary picking machine on the farm. Today modern machinery operated by two men is used for picking and cleaning the hops. However harvesting is not finished when the hops have been picked.
Optimum treatment of the hops after picking
The hops are green material with a moisture content of 80-85 % and have to be dried immediately to 11% moisture content to prevent them spoiling. Via conveyer belts at the same time the green hops are transported into the 14-15 m tall hop kilns and dried at a temperature of 62-65° C within a six hours. The optimum moisture content of hops fresh from the kiln is between 9-10 %. By aerating with circulating air the different moisture contents of the inhomogeneous hops are equalized and at the same time the moisture is balanced between strig and bracteoles. The aim should be to dry the hops in such a way that the required moisture content is reached as soon as the hops are aerated with circulating air.
Aims in drying hops are
preserving the quality of the harvested hops
optimum and economic drying performance
In addition the following principles should be observed:
Optimum drying temperature
Low kiln depth
Time adapted for drying.
Aims in conditioning hops
To maintain and secure the hop quality
Optimum hop moisture
Optimum aerating time
Nowadays the hop harvest requires expensive, complicated technology. An average farm with 15 hectares under hops needs 180 labourers to pick the hops by hand. With modern harvesting technique he can harvest and dry his hops with four labourers. Although for this he needs harvesters costing approx. 125.000 EUR as well as a building for the kiln and stores with equipment valued at 150.000 EUR. Today the hop-grower can only be competitive with this modern technology.
* © Extract from the LfL - Bavarian State Research Centre for Agriculture