Cut the Crap about “Low Temperature” Hop Drying
Hey there Hop Fans…for once I get to take a back seat to an absolute AUTHORITY on food product quality, especially hops.
There is so much hyperbole around hop drying that it is cringe-worthy. Time to set the bar with authority and expertise. Gang, I introduce Mr. Daniel Dettmers, leading expert on food processing quality and preservation, world-wide.
How low can you go? The truth about “Low Temperature Drying”
Sorry if it seems I’m boasting, but Gorst Valley was (and still is) the pioneer in low temperature drying for the hops industry.
The term “low temperature” seems to have many growers and brewers confused. What is Low Temperature?
Let’s explore this concept and see what is possible.
Is heat a bad thing for hops?
Heat is bad. Period. End of story.
OK, heat helps moisture evaporate, which is good. We want that moisture to leave our hops to prevent rot.
But heat also drives away oils, aromas and all the wonderful flavors we want from our hops to flavor our beer. At 100F, the oils and aromas evaporate quickly. At 140F, the heat breaks down alpha acids and we lose bittering potential. Above 160F, the hops rapidly turn yellow like straw and taste about the same. No one goes much above 140F but many define “low temperature” drying as 135F. Is that really as low as we can go? 5 little degrees? Isn’t 135F still driving away many of those flavoring compounds?
Why add heat then?
The drying process is dictated not by temperature but by the relative humidity (RH) of the air. The lower the RH, the thirstier the air is. Thirsty air grabs more water from the hops and dries them out faster.
So how do we lower the relative humidity? The easiest way is to heat the air. It doesn’t remove existing moisture but it does increase the holding capacity of the air. So the warmer the air, the lower the RH. Air at 50% RH and normal temperatures can drop to an RH under 10% at 140F. This gives us a huge drying potential and can dry out our hops very quickly…but at the cost of crappy hops.
Is there an alternative to heat?
There’s always alternatives but everything has a cost. Air at ambient (outside) temperatures below 100F does a fine job of drying down to a hop moisture content of 20% or less. What’s the draw back? It takes more air (i.e. bigger fans) and more time. If the relative humidity falls low enough, hops can be dried using nothing but ambient air.
In areas with naturally high outdoor humidity, we cannot rely on having a dry day (i.e. low RH) to dry our hops properly. What we can do is use that outside air to drive most of the moisture out and then use little heat or a lot of dehumidification to finish off the drying process.
By keeping the drying process at 100F or less, the hops can retain significantly more oils, aromas and other things that makes our beer taste so good
Why not go colder?
Often we have heard, “If ambient temperature is better, then I’ll go lower. I’m going to dry my hops in my walk-in cooler.” Slow down there cowboy, that’s a bit too low. As the air temperature goes down, the relative humidity goes WAY up. A walk-in cooler typically runs at a relative humidity of 80% or better and can only remove minute amounts of moisture. The hops will slowly rot in their cool environment.
What is Low Temperature Drying then?
Gorst Valley would like to set the bar for the industry…and set it low. In our dictionary, “Low Temperature Drying” means drying at 100F or less without any unnecessary heat addition to the process. This is our AromaSmart process and we extend it all the way through our pelletizing process.
“Wait!” you say. “What does ‘unnecessary’ mean? Ah-ha! You are still adding heat at the end of the drying process!” No, it gets cold in Wisconsin. During some of our late season harvests, the night time temperature can drift near the freezing range so it’s sometimes necessary for us to warm the air up to keep the hops from freezing but this is rare.
What’s the drawback of true low temperature drying? It takes us a longer. As much as 5 times longer but we feel this extra effort is worth it to produce the highest quality hops possible.
The AromaSmartTM Pledge
At Gorst Valley Hops, we pledge:
- No Heat. If it is 75F degrees out, we will be drying those hops at 75F to preserve the flavors and aroma’s for our brewer’s kettles.
- We use dehumidfictaion. We have linked up with a dehumidifier manufacturer that leads the way in providing dehumdfiers to the agricultural industry. No heat added to finish drying our hops.
- We keep it cold. Our hops travel from the dryer to the baler to the cold storage where they stay until they are run through the pelletizer while covered in a blanket of cryogenic nitrogen. It keeps the pellets below 100F while chasing away the oxygen. Oxygen is worse than heat during processing.
- Vacuum packed and frozen until they reach the kettle. Why put all this work into quality if we aren’t going to protect the final product?