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Project
System Changes in Wort Production for the Improvement of the Flavour Stability of Lager Beer
The objective of the research project is to study the impact of aninnovative wort production method on flavour quality and flavour stability of lager beer. The innovation comprises 1) thick and fast mashing under anti-oxidative conditions to save time and energy; 2) high mashing-off temperature (95°C) compared to conventional mashing-off temperature of 78°C; 3) acidified sparging; and 4) in-line wort stripping with culinary steam and in-kettle stripping during filling of the kettle (till kettle is full) for continuously stripping of unwanted volatiles. After wortfiltration and in-line stripping, no additional boiling is required. Special attention was paid to mashing-in conditions (O2, pH, temperature),in order to prevent early oxidation. During transfer of the mash to themash vessel, the malt aldehydes are to be stripped off as much as possible. Clean steam injectors in combination with over-sized chimneys and condensate traps and high mashing-off temperatures should facilitate the release and stripping of unwanted volatile aldehydes. Mashing-off at temperatures above 95°C has three aims: 1. strip off unwanted volatile aldehydes; 2. partially degrade of SMM to DMS (flavour of Brussels sprouts);3. coagulate and flocculate high molecular weight proteins. The holdingtime of the elevated mashing-off temperature will depend on these threeitems.
The fastest and thickest mashing conditions were first evaluated to produce concentrated mashes in the shortest time frame. A thick mash results in smaller total volumes so that low water and reduced energy input is required during mashing. An efficient sparging will thenlead to lowest volumes for boiling with highest extract content which is again beneficial in view of energy consumption and brewhouse capacity.
Fine milling in combination with thinbed wort filtrationresulted in highly comparable wort, beer, and ageing profiles compared to conventional coarse milling/lautertun operations.
High mashing-off temperature resulted in a fast wort filtration, bright sweet wortand a low heat load (based on the TB-Index). Due to the high mashing-off and wort filtration temperature, SMM is already transformed into free DMS which evaporates partially at mashing-off. Sufficient conversion of SMM and removal of DMS is possible by in-line and in-kettle clean steam injection during filling of the combination vessel. Sparging with acidified water at high temperature minimised the extraction of extra proanthocyanidins during the sparging step ending up with comparable amounts compared to conventional wort production. High mashing-off temperature alsoresulted in decreased levels of haze sensitive proteins, in comparison with conventional mashing-off temperature. The use of steam to form and strip DMS however results in the formation of a low trub content, but the small protein flocks are difficult to remove. No striking differences have been found when comparing conventionally produced beers with the innovative beers. However, important differences have been observed when the beers were subjected to ageing. Due to the acidified sparging, high aldehyde contents have been found in the pitching wort upon innovative wort production. The low pH of sparging liquor seems to result in an enhanced release of imine-bound aldehydes. As apparent from analysis of pitching wort, these free aldehydes have not been efficiently stripped off (in contrast to DMS), but after fermentation, comparable levels of free aldehydes were found in the fresh beers. However, during ageing of the innovative beer, lower levels of aldehydes were found resulting in significantly lower overall ageing sensory scores. The release of aldehydes during acidified sparging, even at conventional sparge temperatures of 78°C,is also malt dependent. In conclusion, the innovative wort production, executed in less than 3.5 hours, results in a highly comparable fresh beer, but with an extended flavour stability compared to conventional beerproduction. Concentrated mashes and highest extract content due to low sparge rates will result in a decreased need of energy for wort production. The high throughput of the two vessel brewhouse with a thinbed filter will also reduce the investment cost.
The fastest and thickest mashing conditions were first evaluated to produce concentrated mashes in the shortest time frame. A thick mash results in smaller total volumes so that low water and reduced energy input is required during mashing. An efficient sparging will thenlead to lowest volumes for boiling with highest extract content which is again beneficial in view of energy consumption and brewhouse capacity.
Fine milling in combination with thinbed wort filtrationresulted in highly comparable wort, beer, and ageing profiles compared to conventional coarse milling/lautertun operations.
High mashing-off temperature resulted in a fast wort filtration, bright sweet wortand a low heat load (based on the TB-Index). Due to the high mashing-off and wort filtration temperature, SMM is already transformed into free DMS which evaporates partially at mashing-off. Sufficient conversion of SMM and removal of DMS is possible by in-line and in-kettle clean steam injection during filling of the combination vessel. Sparging with acidified water at high temperature minimised the extraction of extra proanthocyanidins during the sparging step ending up with comparable amounts compared to conventional wort production. High mashing-off temperature alsoresulted in decreased levels of haze sensitive proteins, in comparison with conventional mashing-off temperature. The use of steam to form and strip DMS however results in the formation of a low trub content, but the small protein flocks are difficult to remove. No striking differences have been found when comparing conventionally produced beers with the innovative beers. However, important differences have been observed when the beers were subjected to ageing. Due to the acidified sparging, high aldehyde contents have been found in the pitching wort upon innovative wort production. The low pH of sparging liquor seems to result in an enhanced release of imine-bound aldehydes. As apparent from analysis of pitching wort, these free aldehydes have not been efficiently stripped off (in contrast to DMS), but after fermentation, comparable levels of free aldehydes were found in the fresh beers. However, during ageing of the innovative beer, lower levels of aldehydes were found resulting in significantly lower overall ageing sensory scores. The release of aldehydes during acidified sparging, even at conventional sparge temperatures of 78°C,is also malt dependent. In conclusion, the innovative wort production, executed in less than 3.5 hours, results in a highly comparable fresh beer, but with an extended flavour stability compared to conventional beerproduction. Concentrated mashes and highest extract content due to low sparge rates will result in a decreased need of energy for wort production. The high throughput of the two vessel brewhouse with a thinbed filter will also reduce the investment cost.
Date:1 Oct 2008 → 5 Jul 2013
Keywords:Flavour stability, Wort production
Disciplines:Food sciences and (bio)technology
Project type:PhD project