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Old 06-10-2013, 06:10 PM   #1
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Default GVH Drying Method

I’ve had an unusual number of requests for an explanation of my drying method as of late, so I figured I would start a new thread to explain.
For those that don’t know, my name is Dan and I’m the Process Design Engineer for Gorst Valley Hops. We are a hop grower/processor based in Wisconsin with growers spread across the Midwest. We’ve gained a fair amount of respect among the Midwestern brewers for our consistent supply of higher-than-average quality hops.

What’s our secret? Part of it is the growing methods we have developed for the Midwestern climate but a lot of it comes from breaking with traditional drying methods of the PNW (Pacific Northwest) and doing our own thing. I developed this method from over a dozen years working in the food processing/refrigeration industry. I literally stole ideas from pea freezing, packaged cake cooling and my curling club to come up with this.

Let me lay this idea out over several posts. Sorry for the wordiness but no one has ever accused me of being a man of few words.

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Old 06-10-2013, 06:11 PM   #2
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Step 1: Forget everything you think you know and realize that hops are closer to roses than malt.

It’s traditional to “kiln” the hops by heating them up to 140F to drive out the moisture. In actuality, the heat really does very little to the rate at which the moisture leaves the cone. The purpose of the heat is to lower the relative humidity of the air allowing it to absorb more moisture from the hops. Heating to 140F will drop the RH below 10% in almost any climatic conditions. This is important if you are harvesting 10’s of acres every day and need to dry it in 24 hours, as they do in the PNW. This is not the case for the home grower or the small commercial grower.

When you raise the temperature to drive out the moisture, you also increase the evaporation rate of the oils and aromas. Anything above 90F will rapidly push out the oils. True, the alpha acids will remain and give you the bittering, but the “flavor” you desire is gone. Again, treat them like roses to preserve the oils and aromas.

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Old 06-10-2013, 06:11 PM   #3
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Step 2: Understand this: to remove moisture you either need to increase the amount of air touching the hops, lower the relative humidity or both.

First, we will focus on increasing air contact. The way moisture is removed from hops is via air. The more air that touches the hops, the more it can remove…period. It doesn’t magically disappear when it’s trapped in a grocery bag, it doesn’t vaporize in high heat, it can’t escape from a grocery bag, placing them in an air tight plastic tote with a fan blowing the air in circles doesn’t move it away…air has to carry it away, far away, into the great outdoors. If you understand this, you can see why putting the hops in a paper bag, plastic bag or anything that restricts air contact/air movement would not work. Instead we have two choices: spread them out very thin on a screen or force air to blow through them.

For the home grower, laying them out in a flat layer is the best option. An old screen door works well because it allows air to contact both the top and the bottom of the hop bed. Don’t make that bed too deep or the air won’t be able to remove moisture from the hops in the middle.

For anyone with 10 or more plants (of a single variety), this method would require WAY too many screen doors. Therefore you need to set up some method to blow air through the hops. That’s a much longer discussion about CFM, pressure drop and velocity that I won’t go into here but some key items to remember include:

- The more air the better. Increase the CFM/velocity to increase the amount of air contacting the hops.

- Be careful of velocities that are too high, especially if blowing up through the bed. As they dry, they become lighter and could blow out of your dryer or at least shake the lupulin out of the hops.

- Selection of a fan is more than CFM, it has to be CFM at the necessary pressure drop

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Old 06-10-2013, 06:12 PM   #4
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Step 3: Make sure you are getting rid of the moisture

Too often I hear this, “I’ve got a fan blowing on my hops and the moisture is leaving them but I have another problem. There water running down the walls in my shed and it smells like mold.”

For every 1 pound of dried hops you expect to get, you need to get rid of approximately 4 pounds of moisture. This is A LOT of water. If you let them dry in a closed space, the air will rapidly saturate with moisture (hit 100% RH). That moisture will now condense on any surface it can find, like walls, ceilings and floors. It will also be so saturated that it will not be able to take any more water from the hops, regardless of the size of fan you use.

BE CERTAIN YOU ARE BRINGING FRESH AIR INTO THE ROOM YOU ARE DRYING IN.

A common misconception is that if it is raining outside, you should close the doors and windows to keep the moist air out. Using air at 99.9% relative humidity, you can still remove over 50% of the moisture. So if you are in the first 24 hours of drying, leave the windows open and let the fresh air in. It will remove more moisture than if you put those hops in a sealed up room. Again…

BE CERTAIN YOU ARE BRINGING FRESH AIR INTO THE ROOM YOU ARE DRYING IN
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Old 06-10-2013, 06:13 PM   #5
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Step 4: Lowering the relative humidity if needed.

For the homegrower, you want to get the moisture content of the hops down to 15% or less. Commercial growers are shooting for 12% or less depending on what is to be done for further processing.

Some of you (e.g. Colorado, Arizona, Nevada) will easily be able to reach that level using only outside air in 48 hours. The rest of us may need some help, especially if it is a humid week.

Again, the lower the relative humidity, the larger the driving force to pull moisture out of the hops and into the air. The big guys in the PNW achieve this by heating the air up so the whole drying process can be completed in 24 hours. Are you in that big of a rush? Probably not. So slow down and let them dry at lower temperatures.

If you have gone 2 days and they are not dry, its probably time to take it to the next step. On ideal location for most homegrowers is in an air conditioned house is wonderful but most SWMBO won’t put up with that smell.

Your next best option is to put them in a closet with a dehumidifier. If there is no closet available, get a tarp or piece of plastic and build a little tent around the hops and the dehumidifier. The smaller the space, the faster the hops will dry. If you try to dehumidify a large space (e.g. basement, kitchen) or a leaky space (e.g. garage), the dehumidifier will be too busy with that load to be able to take care of your hops. If you put them in a tiny place, the dehumidifier should quickly dry the hops out.

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Old 06-10-2013, 06:14 PM   #6
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Step 5: When am I done?

As previously mentioned, you want to get well under 20% moisture content…meaning you want the hops to get to 1/4th to 1/5th of the original weight. Then you are free to package them up and pop them in your freezer for later use.

Following this method, you should be able to get down to 20% moisture content in 24 hours. One of the indicators is that the cone starts to open up like a pine cone that has fallen to the ground. They will also feel brittle with some of the bracts (leaves) easily falling away. If you snap them in half, the strig (stem) will still feel a moist when pressed to your lips, though.

Now bring them in the house or put them in a dehumidified tent. Depending on the size of the dehumidifier and the amount of moisture to be removed, the remaining time could be 1 hour to 2 days. When they are dry, the strig should still be a little supple but not moist. A few of the outer bracts may fall away but the whole cone shouldn’t shatter. If they are falling apart and turning to dust, you’ve hit 6% or less and way over dried.

To prevent overdrying, either check often or use a dehumidifier that you can set an RH setpoint of 45%. At 50%, the hops will equalize out to around 8.3% moisture content. This way they won’t overdry on you too quickly.

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Old 06-10-2013, 06:14 PM   #7
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Summary
Lay them out on a screen 1 cone deep in a cool, dry area. Feel free to have a fan blowing lightly over them to move air across the hops.

BE CERTAIN YOU ARE BRINGING FRESH AIR INTO THE ROOM YOU ARE DRYING IN.

If you have too many hops to lay out on a screen, set up a drying apparatus that will blow air through them. Higher velocity is better, so ignore the PNW practice and blow DOWN through the hops. This way, you can use the strongest fan you can and they won’t blow away.

If you have waited 24 hours and they are not 23% of their original weight, put them in the smallest area you can with a dehumidifier or an air conditioned space.

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Old 06-10-2013, 06:22 PM   #8
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That all sounds perfectly logical to me. I made three frames that hold large window screens, which each can hold about three pounds of cones without them layering. I stack them across a pair of saw horses with two 20" box fans perched on milk crates below, cover the top layer with screening, surround the stack with random pieces of plywood, and let 'er rip. I run the fans at high speed for the first 24 hours, then drop down to medium speed, where dry cones will dance a bit but not violently, and I can usually get the moisture content below 20% in 48 hours.


Cheers!

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Old 06-10-2013, 06:27 PM   #9
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Thanks!

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Old 06-13-2013, 04:39 PM   #10
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sticky?

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