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Influence of Hopping Technology on Oxidative Stability and Staling-Related Carbonyls in Pale Lager Beer
Wietstock, P. C., Kunz, T. and Methner, F.-J.

Storage-induced deterioration of beer flavor is a major issue for many breweries and technological measures to diminish staling are limited. In this study, the effect of different hopping technologies on content of pro-oxidative iron ions, concomitant oxidative beer stability and staling-related carbonyls was investigated. In lab-scale brewing trials, hop dosages during mashing-in or at the onset of boil caused a decrease of pro-oxidative iron ions in dependency of the amount of hop CO2 extract dosed. Though, the effectiveness was clearly limited by the ‘accessibility’ of iron ions. The amount of ‘free’ iron was found to be dependent on the initial malt bill, and the hops’ efficiency in terms of reducing the iron content was higher the more iron was present and the more hop CO2 extract was dosed. Pilot-scale brewing trials (120 L) were carried out in duplicate using different hopping technologies: hops dosed only at the onset of boil (reference), mash hopping, divided hop dosage, first wort hopping, and continuous hop dosage. Hop CO2 extract was the sole hop product used. While standard beer quality parameters were unaffected from the hopping, the bitter substance yields suffered from later hop dosages or in particular from hop dosages during mashing. All brews with modified hoppings showed reduced iron contents of up to ~30 % and improved oxidative stabilities as compared to the reference brews with the exception of the first wort hopping brews where the oxidative stability as measured by electron spin resonance spectroscopy was worse. After storage (12 weeks, 28 °C), the staled beers’ carbonyl contents were noticeably distinguishable and were lowered up to 66.9 % when modified hopping was applied. Sensory analysis of the fresh and aged beers was in accordance with the analytical data and revealed improved sensory properties for the beers produced by applying modified hopping regimes with the exception of the mash hopping brew from brewing series 2, whose sensory properties were rated lower. This study provides new findings with regards to the anti-staling characteristic of hops and its application by simple modifications of the hopping technology.

Descriptors: Hop dosage, hops, beer ageing, mash hopping, first wort hopping, continuous hopping, aldehydes, iron

BrewingScience - Monatsschrift für Brauwissenschaft, 69 (November/December 2016), pp. 73-84