Increasing the hop alpha-acids utilization by hop pre-isomerization and the evaluation of the bitter quality of beer

Technical Session 04: Hops II Session
Seiichi Takishita, Asahi Breweries, Ltd.
Co-author(s): Hisato Imashuku, Asahi Breweries, Ltd., Japan; Martin Krottenthaler, Hochschule Weihenstephan-Triesdorf, Germany; Thomas Becker, Technische Universität München, Germany

ABSTRACT: Our colleague, Hisato Imashuku, presented PIE (pre-isomerizer and evaporator) at WBC 2008. This is a system in which hops are boiled with hot water separately from the wort. By using this system, we can save energy, improve the hop alpha-acids utilization, and so on. In this study, further improvement of the alpha-acids utilization using PIE was investigated, and the bitter quality of beer was evaluated. First, optimization of hop pellet PIE treatment conditions at the laboratory scale was conducted. In consequence, boiling 60 min under pH 8.0 using KOH (at the onset of boiling) was the best condition. Secondly, some brewing trails with 70% malts and 30% syrup adapting the abovementioned PIE condition were done at a 60-L scale pilot plant. The influence of the time when PIE-boiled hops are dosed to wort/beer, the influence of aged hops, and the influence of different hop varieties were the focus of the study. Concerning the time of dosing PIE-boiled hops, there was no significant difference in alpha-acids utilization with different dosing time, during boiling, at the beginning of fermentation and at the beginning of maturation. Maximum alpha-acids utilization was approx. 67%, which was only approx. 2 and 10% lower than using isomerized kettle extract and isomerized extract, respectively, and >1.5 times higher than conventional hop dosing. There was no significant difference in the bitter quality of beer, in spite of the different dosing times for PIE-boiled hops. Concerning the influence of aged hops and different hop varieties, there was no significant difference in the rating of bitter quality between using PIE and the conventional method. Nevertheless the character of bitterness changed slightly, and we presume that it is related to the amount of non-isohumulone bittering compounds in the beer. As a result, this could make it possible to control the character of bitterness in beer.

Seiichi Takishita graduated in 1999 with a master’s degree in agricultural and life sciences from the University of Tokyo, Japan. He began employment with Asahi Breweries, Ltd. in 1999 as a technical staff member in the brewing section. After he had worked at several of the breweries and Development Laboratories for alcoholic beverages, he worked as a visiting researcher at the Technology University of Munich from 2010 to 2012.