Zac German, technical manager at Yakima Chief-Hopunion LLC in Yakima, WA, has analyzed hundreds of hop samples from around the country. What he has learned can help hop growers capitalize on one of the fastest-growing segments of the craft beer industry. “Breweries are opening at the rate of one every 18 hours,” says German. Unique hops distinguish one beer from the next, but unlike wine, which varies from one vintage to the next, brewers are expected to produce beer that is consistent. “There are huge variations in alpha; bigger than you might expect for a given variety,” says German. “It makes me wonder if all of the hops that are being sold are true to type. It’s easy to get contaminate rootstock, so that’s one thing to be aware of,” he adds.
The bottom line is whether the hop grower is growing for alpha or for oil. “This comes down to how the hops will be used — as a bittering addition or an aroma addition,” says German. Rootstock is an important factor that contributes to hop quality, “Variability in alpha and oil can go in all directions,” says German, adding “In the Yakima Valley, hops are propagated mostly by digging rhizomes, if you have a Cascade field and there’s one nugget out there and you dig up rhizomes, you’ve pulled ten rhizomes from that one Nugget that shouldn’t be there. Then when you plant them, you have 10 Nuggets in your next field. Be very careful of where you’re getting rootstock — it’s very easy for that contamination to propagate from one generation to the next.”
Another consideration is that rootstock tends to accumulate disease over time, so the older the yard, the more variability in quality. German suggests purchasing certified rootstock or rootstock from the NCPN (National Clean Plant Network). “The presence of males is another issue,” he adds. “The more males, the more pollen and if there’s pollen flying around, it’s going to pollinate the females (cones) and you’ll have a lot of seed. If you have four or five percent seed, which is high but not uncommon, that’s five percent of your product that has no alpha, or oil, because it’s basically watered down with seed content.”
In addition to his extensive lab experience, German is a brewer. High oil, low alpha hops appeal to him. “Brewers are putting huge amounts of hops in beer,” he said. “Two pounds per barrel, four pounds per barrel. Getting a bitter beer is not very hard these days.” German says to maximize aroma, he likes to uses hops that he can get a lot of oil out of without over-bittering.
German explains that hops used for bittering are boiled for a long time to stabilize the bitterness. The downside of boiling for a long time is that a lot of the unique aromas such as florals, citrus and fruits are cooked off. “Brewers have a lot of choices for adding bitterness,’ he said. However, the unique aspects of hops shine when they’re used for aroma. Going for aroma means highlighting the unique qualities of the hop and that’s what makes the beer unique and sets breweries apart. For aroma, hops are boiled for a short time or not boiled at all. “The majority of hops in the craft brewing industry are being used for aroma,” said German. “We aren’t seeing a lot of long bittering additions; instead there is a lot of dry hopping. You’re extracting as much bitterness per unit of hop yet retaining a lot of the aroma.”
How pellets are used also makes a difference in the end product. “If you have a really dense, glassy pellet, boiling the pellets isn’t a big deal because with all of the agitation, the pellets come apart,” says German, adding “but now, with brewers doing a lot more dry hopping, the pellets are added to the finished beer. That means that there isn’t a lot of agitation and the tank is cold. If you dump a box of hard pellets in, they fall to the bottom of the tank and the aromatic quality isn’t extracted.”
How can growers achieve oil versus alpha? One factor is harvest time. “I suspect that folks are harvesting too early,” says German. “All else being equal, if you can harvest later, you’ll have higher oil content.” As hops mature, they start to dry. Measuring moisture content of the cone helps determine time for peak harvest. Aim for about 22 to 23 dry matter, but remember that figure varies by variety. The good-old fashioned tactile test helps: if the hop feels oily, or has a grassy, vegetal green aroma, it isn’t ready.
Once hops are harvested, quality can decline rapidly. Light, heat, oxygen and moisture are all enemies of harvested hops. “Ideally, pick cones and start drying within hours of cutting,” says German. “Even if you’ve nailed the oils and done everything else right, if you put them in a bag and they’re too wet, they’ll smell rotten almost immediately. Too much water dilutes oil and alpha content,” he points out.
German believes that early picking is common because no one wants to let hops sit out too long, he believes blowing heat and oxygen on hops is a bad idea. “The outer bracts dry out and get papery and crispy but the inner strig is holding a lot of moisture. Then when you bag them up, the moisture equalizes from the inside out and you end up with a 20 percent moisture hop that gets soggy.” he explains. “Our main rule for hops processing is no birds, no sticks and no poop — these are things that brewers notice,” says German, “If you open a bale and find any of these things, it’s no good.” For kilning, German says the target temperature should be 125 to 140 degrees. “Conventional wisdom is that lower temps are better, but there isn’t a lot of data to back that up,” he says, “especially considering the risk of underdrying. It’s better to start at a high temperature, then lower the temp as hops dry. Maximize airflow to carry the moisture away.