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Title: System Changes in Wort Production for the Improvement of the Flavour Stability of Lager Beer
Other Titles: Systeemwijzigingen in wortproductie voor de verbetering van de smaakstabiliteit van pilsbier.
Authors: De Rouck, Gert
Issue Date: 5-Jul-2013
Abstract: The objective of the research project is to study the impact of an innovative 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 wort filtration 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 the mash 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 holding time of the elevated mashing-off temperature will depend on these three items.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 then lead 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 filtration resulted 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 wort and 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 also resulted 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 beer production. 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.
Table of Contents: TABLE OF CONTENTS
LIST OF ABBREVIATIONS AND SYMBOLS ix
CONTEXT AND AIMS OF THIS STUDY xi
CHAPTER I. WORT PRODUCTION: A REVIEW 1
I.1. Introduction to the conventional wort production 2
I.2. Milling and mashing 3
I.2.1. Impact of milling and mashing on wort quality 3
I.2.2. Fine milling technology 7
I.3. Lautering 9
I.3.1. The impact of milling and mashing on the lauter performance 9
I.3.2. Filter cycle in case of membrane assisted thinbed filter operations 13
I.4. Boiling 16
I.4.1. Introduction 16
I.4.2. Critical comments with regard to conventional wort boiling 17
I.4.3. Importance of the construction of a boiling kettle 19
I.4.4. Conventional Boiling systems 19
I.4.5.Wort ‘boiling’ with extra stripping 23
I.4.6. Advanced boiling systems 27
I.5. Relation between wort production and beer flavour stability 29
CHAPTER II. THE INFLUENCE OF VERY THICK AND FAST MASHING CONDITIONS ON THE WORT COMPOSITION 39
II.1. Introduction 40
II.2 Materials and Methods 40
II.2.1. Malt 40
II.2.2. Wort production at lab scale 41
II.2.3. Beer production 42
II.2.4. Wort analyses 42
II. 3. Results and discussions 45
II.3.1. Influence of milling, mashing-in temperature and pH on attenuation limit and FAN levels 45
II.3.2. Effect of mash thickness and short mashing programs on the extract yield, AAL, FAN levels and sugar composition 53
II.4 Conclusion 64
CHAPTER III. THE IMPACT OF WORT PRODUCTION ON THE FLAVOUR QUALITY AND STABILITY OF PALE LAGER BEER 65
III.1 Introduction 66
III.2. Materials and Methods 66
III.2.1. Conventional wort production - coarse milling (CM) 66
III.2.2. Conventional wort production - fine milling (FM) 67
III.2.3. Analyses 67
III. 3 Results and discussions 70
III.3.1. Brewing performance 71
III.3.2. Comparison of pitching wort 72
III.3.3. Comparison of fresh beers 76
III.3.4. Comparison of beer ageing 79
III.4 Conclusion 81
CHAPTER IV. SUFFICIENT FORMATION AND REMOVAL OF DMS WITHOUT CONVENTIONAL BOILING 83
IV.1 Introduction 84
IV.2. Materials and Methods 84
IV.2.1. Conventional wort production – coarse milling 84
IV.2.2. Conventional wort production – fine milling 85
IV.2.3. Innovative wort production 85
IV.2.4. Headspace SPME GC-PFPD analysis of DMS and DMS precursor in wort and beer 85
IV.2.5. Gas chromatographic analysis of trihydroxy fatty acids 86
IV.3 Results and discussions 86
IV.3.1. Determination of DMS 86
IV.3.2. Determination of DMS precursor 87
IV.3.3. The influence of milling on DMS formation and evaporation in conventional brewing trials 89
IV.3.4. DMS formation and evaporation during innovative brewing trials 92
IV.4 Conclusion 96
CHAPTER V. IMPACT OF HIGH MASHING-OFF TEMPERATURE ON LAUTER PERFORMANCE AND WORT COMPOSITION 99
V.1. Introduction 100
V.2. Materials and Methods 101
V.2.1. Conventional wort production - fine milling 101
V.2.2. Innovative wort production 101
V.2.3. Innovative wort production with additions to improve protein flocculation 101
V.2.4. Analyses 101

V.3. Results and discussions 102
V.3.1. Influence of high mashing-off temperature on wort composition 102
V.3.2. Improved protein flocculation and hot wort clarification 108
V.3.3. Evaluation of final beer quality 110
V.3.4. Energy consequences of mashing-off at 95°C 113
V.4. Conclusion 114
CHAPTER VI. PROLONGED BEER FLAVOUR STABILITY BY IMPLEMENTATION OH HIGH TEMPERATURE MASHING-OFF AND ACIDIFIED SPARGING 115
VI.1 Introduction 116
VI.2 Materials and Methods 116
VI.2.1. Conventional wort production - fine milling 116
VI.2.2. Innovative wort production 117
VI.2.3. Analyses 117
VI.3 Results and discussions 117
VI.3.1. Analysis of first wort 118
VI.3.2. Analysis of pitching wort 119
VI.3.3. Analysis of fresh beer 122
VI.3.4. Analysis of aged beer 124
VI.4 Conclusion 127
CHAPTER VII. GENERAL CONCLUSIONS AND FUTURE PERSPECTIVES 129
VII.1. General conclusions 130
VII.2. Future perspectives 135
References I
Publication list XIX
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Centre of Microbial and Plant Genetics
Microbial and Molecular Systems - miscellaneous
Centre for Food and Microbial Technology
Technologiecluster Bioengineering Technologie
Bioengineering Technology TC, Technology Campuses Ghent and Aalst

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