Sour wort concentrate as an efficient alternative to traditional biological acidification or the use of acidified malt Jean Titze , Mareike Beermann , Stefan Blieninger and Axel Kaltenbrunner 1) 2) Döhler GmbH · Landshuter Brauhaus 1),*
1)
2)
1)
Figure 2 shows that the main fermentation of brew C took 7 days. In contrast, brew A and brew B were finished only after 8-9 days which shows the very good effect of the use of SWC on the fermentation performance.
Introduction Assuring a constant beer quality is one of the biggest challenges in the brewing industry. Here, taste stability plays a major role [1]. Additionally, a “perfect taste” is still the main reason for consumers to buy a beer. Consequently, the method of mash and wort acidification is very common in the brewing industry because it results in a considerably faster and better brewing process and leads to a higher beer quality with enhancement of the sensory quality and stability. But due to the upcoming trend of naturalness, biological acidification with sour wort is preferred instead of the use of pure acids. For this, a cost intensive, separate fermentation plant is necessary. In this context, a sour wort concentrate (SWC) was developed which was produced by concentrating traditionally produced sour wort with the help of a vacuum fall stream evaporator. Its application was evaluated and compared with the use of acidified malt, another natural way of acidification in the brewhouse.
Materials & Methods To evaluate the positive effect of SWC, brewing trials were run in a 200 hL brewhouse by setting various conditions: As a reference, 5% of sour malt was used (brew A). In another brew, 5% of sour malt was used as well as SWC was added to the wort (brew B). Finally, instead of the use of sour malt, SWC was added to the mash and the wort (brew C). The acidification took place in the brewhouse (Figure 1). The final beer type was a filtered Bavarian “Helles” (pale lager).
Malt
AND / OR Wort acidification
Sour wort
Sour wort
pH = 5.2 - 5.4
The fresh bottled beer as well as the artificial aged beer (applying a standardized forcing method) were tasted by sensory experts in Weihenstephan.
pH = 5.0 - 5.1
Whirlpool
Fig. 1. Usage of sour wort in the brewhouse to lower pH in a natural way.
Table 1. Wort analyses of the cold wort.
Brew C
Method [2]
Original gravity
% w/w
11.78
12.01
12.08
WBBM 2.9.6.3
Alcohol
% v/v
5.22
5.38
5.42
WBBM 2.9.6.3
Extract
% w/w
1.94
1.88
1.88
WBBM 2.9.6.3
Attenuation limit
%
84
85
85
WBBM 2.8.1
pH
-
4.54
4.47
4.37
WBBM 2.13
Colour
EBC
6.25
6.25
5.80
WBBM 2.12.1
TPO (total package oxygen)
mg/L
0.148
0.135
0.133
WBBM 2.28.3
Soluble oxygen
mg/L
0.091
0.087
0.094
WBBM 2.28.1
Additionally, the fresh bottled beers were artificial aged by performing a standardised forcing test. Both, the fresh and aged beers of all three brews were examined to their thermal, oxygen and staling indicators (Figure 3). Especially the results of the aged beers show, that the indicators are decreasing (A>B>C). 300
Brew A
Brew B
250
Brew C 200
150
100
50
Fig. 3. Compilation of the thermal, oxygen and staling indicators of fresh and aged beer.
0
Sum of thermal indicators
Sum of oxygen indicators
Sum of staling indicators
Sum of thermal indicators
Sum of oxygen indicators
Sum of staling indicators
Aged beer
Fresh beer
The objective analyses in Figure 3 could be verified by a sensorial testing (Table 3): the beer of brew C showed the best taste stability with a value of 0.23. Table 3. Results of the tasting panel of Weihenstephan. Brew A
Brew B
Brew C
Smell
4.0
4.3
4.2
Purity of taste
4.0
4.2
4.2
Body
4.5
4.5
4.5
Carbonation
4.5
4.5
4.5
Quality of bitterness
4.0
4.1
3.9
Smell
3.5
3.7
3.8
Purity of taste
3.5
3.7
3.8
Body
4.5
4.5
4.5
Carbonation
4.5
4.5
4.5
Quality of bitterness
3.0
3.5
3.8
Rating beer fresh
4.13
4.28
4.20
Rating beer forced aged
3.63
3.85
3.98
Taste stability
0.50
0.43
0.23
Beer after artificial aging
Parameter
Unit
Brew A
Brew B
Brew C
Method [2-4]
Extract
% w/w
11.76
11.95
12.03
WBBM 2.9.6.3
pH
-
5.32
5.02
4.98
WBBM 2.13
Colour
EBC
9.50
10.00
9.25
WBBM 2.12.1
Coag. nitrogen3)
mg/100 mL
2.65
2.91
2.89
WBBM 2.6.2
TBI3)
-
55.31
56.74
48.18
WBBM 2.6.2
DMS free3)
µg/L
108.16
97.41
98.75
MEBAK III 1.3
3)
DMS precursor
µg/L
10.20
22.09
21.95
MEBAK III 1.3
Iso-alpha-acids
mg/L
19.9
19.1
19.3
EBC 7.7
values recalculated on 12% w/w extract.
The solely use of SWC in mash and wort led to a reduced colour formation (see also Table 2) and a smaller thiobarbituric acid index (TBI), which is a measure for the cumulative thermal stress brought about exposure to heat (intensity) in wort. The TBI reflects numerous Malliard reaction products in addition to 5-hydroxy-methylfurfural (HMF) and other organic compounds, which formation seems to be suppressed by the presence of SWC. 12
Brew A
11
Brew B
10
Conclusion It turned out, that the acidification while using only sour malt compared to the usage of natural sour wort concentrate (SWC) leads to a poorer beer quality, especially in terms of taste stability. It should be mentioned, that part of the effect and advantages of biological acidification were already given by the use of sour malt in the reference brew (A). However, the effects of SWC were significant compared to the brews with sour malt. SWC is an efficient alternative to the traditional biological acidification without the installation of an extra fermentation plant. By using SWC, all brewers can now acidify not only the mash but the wort as well. Furthermore, the use of SWC is also in accordance with the German Purity Law and permits “clean labelling”.
Brew C
9
Extract [%]
Brew B
Fresh beer
The original mash pH (after mashing-in) would result in 5.48. After lowering the mash pH to 5.3 with sour malt (A, B) or with SWC (C) and the wort pH to approximately 5.0 with SWC (B, C), the cold worts of the three brews were analysed (Table 1).
References
8 7 6 5 4
Fig. 2. Curves of the extract decrease during main fermentation.
Brew A
Parameter
Results & Discussion
3)
Unit
Finally, a sensory evaluation of the beers was conducted by the 5-point-scheme of the German Agriculture Society (DLG e.V.) [5].
pH = 5.2
pH = 5.6 - 5.8
or
Parameter
µg/L
Mash acidifaction
Sour wort
Wort kettle
Table 2. Beer analyses of the final beer.
Wort and beer parameters were analysed applying the standard methods specified by MEBAK and EBC [2-4].
Water
Hop
After a maturation time of 12 weeks, all beers were filtered and bottled. In Table 2, the beer quality parameters are listed.
3 1
2
3
4
5
Fermentation time [d]
6
7
8
9
1. Titze, J., 2010: Qualitätssiegel oder Medaille? – Güte und Sicherheit von Produkten richtig kommunizieren. – Getränkeindustrie 64, no. 10, pp. 52-55. 2. Jacob, F. (Ed.), 2012: Würze, Bier, Biermischgetränke (WBBM). MEBAK, Freising. 3. European Brewery Convention Analysis Committee (EBC), 1998: Analytica-EBC (EBC), Hans Carl, Nuremberg. 4. Pfenninger, H. (Ed.), 1996: Brautechnische Analysenmethoden. Band III. Methodensammlung der Mitteleuropäischen Analysenkommission (MEBAK III), MEBAK, Freising. 5. Deutsche Landwirtschafts-Gesellschaft e.V. (DLG), 2014: Das Testverfahren der DLG für Biere. – URL: http://www.dlg.org/ bierkriterien.html, download 25.04.2014. homepage. * Corresponding author:
[email protected] · Dr. Jean Titze · Döhler GmbH · Riedstraße · D-64295 Darmstadt, Germany
