One of the most common questions we receive around harvest time is “how do I know that my hops are ready to harvest?” We use a few different strategies to determine whether the hops are ready. There is a very traditional sensory test, a more scientific home-based test, and a lab-based test.
Traditionally, hop farmers have determined that their hops were ready for harvesting when the cones begin to feel dry and papery. When the cones are ripe, the yellow lupulin inside the cone should be very obvious, bright, and aromatic. If the cones are soft or damp, it is still too early for harvesting. This sensory test is a good start – you can tell if your hops are ready for harvest or further testing.
The next test we do is a readiness test or moisture test. We randomly test a minimum of 6 sidearms in each hop yard, near the top of the trellis, around noon on the date of testing. We take a sample of around 100 cones, and record the weight. We then dry the hops overnight in a food dehydrator at between 140-150F until the hops are down to 0% moisture. 0% moisture is achieved once the cones reach a stable weight. We then take our dried sample and apply it to the following formula: Hop percent dry matter = 100 x dry cone weight/green cone weight.
Here is a handy online calculator for determining this formula: http://www.uvm.edu/extension/images/engineering/hopscalc.html
To determine whether your particular variety is ready for harvest based on the above formula, you can check with standard target harvest dry matter results here: http://www.uvm.edu/extension/cropsoil/wp-content/uploads/Hop_harvest_fact_sheet.pdf
Finally, if the sensory test and the readiness test seem to indicate that the hop field is harvest-ready, we send a sample to our local lab for testing. This is a new development for us. In the past, we would send our hops post-harvest to the Washington State Department of Agriculture. While this is a necessary step in determining alpha and beta acids and oil content after harvesting, the shipping and turnaround time meant there was not enough time to test the hops prior to harvesting. This changed for us last year with the opening of a local testing lab. Commodity Lab Vancouver is located less than an hour from our main processing facility. When our sensory testing and readiness testing check out, we deliver a sample to the lab, and they are able to return results that afternoon. This allows us to know with certainty that are acids and oils have reached peak levels and that particular field is ready to begin harvesting the next morning.
Harvesting is time-sensitive as harvesting too early can reduce yields from your hop yard and can affect the subsequent year’s yield as well as affecting the flavour of your hops as the alpha acids and oils are not at peak levels. Harvesting too late can also reduce the brewing value of your hops, both in flavour and aroma. Late harvested hops take on a garlic or onion flavour and begin to turn brown – which means your pellets will smell off and look brown as well.
So what’s the optimal moisture level once you have harvested? Hops should be dried down to 8-10% moisture (or 90 – 92% dry matter) for packaging and storage. We aim for a consistent 9% moisture. If you are lucky enough to live within a reasonable driving distance to a lab, by all means make friends and get them to test test your hops for alphas and oils to ensure you are harvesting your hops at the right time.