Japan: Kirin develops technique to create heat-resistant hops

Abnormal weather conditions and rising global temperatures are threatening world-wide production of hops, the key ingredient in beer, The Asahi Shimbun reported on August 14.

However, Kirin Holdings Co. has developed a technique to create heat-resistant hops during the seedling cultivation process without sacrificing their aroma, bitterness and flavor.

The company has filed a patent for the method and presented its research at a conference of the International Hop Growers’ Convention (IHGC) held in Germany in June.

Kirin hopes to put into practice its method of strengthening hops’ heat tolerance to ensure quality as the number of hop farmers in Japan continues to decline.

In 2022, Kirin developed the world’s first technology for mass producing hop seedlings. It will combine this technology with the heat-resistant cultivation method.

Hops, often called the “soul of beer,” normally thrive in cool climates.

“We have found a strong possibility of maintaining hop yields even in high temperatures,” said Riko Imahori of Kirin’s Research and Development Division. “From next fiscal year, we plan to start similar field trials overseas.”

The project began three years ago, focusing on a phenomenon called “heat acclimation,” where plants exposed to mild temperature stress beforehand can survive in high-temperature environments that are not lethal.

The company applied this approach to hop cultivation, working with Saaz hops from the Czech Republic and Hersbrucker hops from Germany, both popular varieties in beer production.

Kirin treated hop seedlings at 25 degrees before cultivation and found they grew well even in high temperatures of 30 degrees. They showed no signs of poor growth.

The same solid growth was observed even after the seedlings were not watered for 10 days to simulate drought conditions.

Field tests on the seedlings were conducted outdoors at two locations in Iwate Prefecture, with a daytime temperature difference of about 2 degrees.

Seedlings pre-treated with heat performed better than the untreated ones at the warmer site. They grew taller and developed more leaves without growth problems, the company said.

Importantly, the hops’ aroma and flavor remained unchanged.

According to the IHGC, the estimated hop production for 2024 was 110,000 tons, a 13-percent decrease from five years ago.

Abnormal weather, including rising temperatures, has been cited for the decline.

In 2023, a Czech research team published in the journal Nature Communications a report titled, “Climate-induced decline in the quality and quantity of European hops calls for immediate adaptation measures.”

According to the study, hop yields in Europe’s main growing regions—Germany, the Czech Republic and Slovenia—are projected to decline by up to 18 percent by the year 2050.

The study also predicts the content of alpha acids, the compounds responsible for beer’s characteristic bitterness, could decrease by as much as 31 percent.

Hops are mainly grown in cool regions known as the “hop belt,” located between 35 and 55 degrees latitude in the Northern and Southern hemispheres.

In Japan, major hop-producing areas are the Tohoku region and Hokkaido. Like farmers in the hop belt in Europe, hop growers in Tono city, Iwate Prefecture, are also experiencing abnormal weather.

“In the past, summer daytime temperatures were around 27 to 28 degrees,” said Junpei Anbe, head of the Tono hop agricultural cooperative.

On the day of the interview with Anbe at the end of July, the daytime temperature reached 33 degrees.

“When it gets too hot, hops flower before fully growing, causing the cones to fall before harvest and reducing yields,” Anbe said. “This has become especially common recently.”

The abnormal weather conditions have also increased the frequency of sudden, intense downpours known as “guerrilla rainstorms.”

While hops need sufficient water to grow, these heavy rains often recede so quickly that the soil cannot absorb enough moisture.

The guerilla storms do not provide the beneficial rain that hop cultivation requires, according to Anbe.

Another serious challenge to Japan’s hop production is the shortage of farmers with the expertise and skills to grow the plants under sensitive conditions.

The aging population and declining rural communities have led to a steady drop in hop farming.

According to the national federation of hop agricultural cooperatives, production plunged from 2,513 tons and 6,682 hop growers in 1970 to just 123 tons and 96 growers in 2023.

Amid these demographic conditions, Kirin started researching heat-resistant hop cultivation to ensure sustainable production.

“Even as global warming worsens, we want to maintain hop yield and quality through this research to continue making delicious beer,” Kirin’s Imahori said.

14 August, 2025