Check your expert knowledge!

How solid is your expert knowledge when it comes to beer brewing? Whether craftsmanship or extensive expertise in the field of microbiology and food chemistry: A brewer needs the knowledge and overview of the entire manufacturing process. This is why the questions in this issue cover a broad range of facts which a professional brewer should be familiar with.

1. Yeast management in the brewery means...

a) the handling of cultured yeasts in the yeast bank in the lab.

b) the process from yeast propagation to pitching to yeast storage.

c) the process of yeast washing after yeast collection.

d) the search for new yeast strains.

2. Breweries can obtain their yeast from other breweries or “produce” it from pure yeast cultures. The yeast propagation plays a central role in this process. What does “yeast propagation” mean?

a) Breeding of new yeast strains with the aid of glucose.

b) Intensive propagation of yeast in wort supported by timed aeration.

c) Preservation of yeast cells using liquid nitrogen.

d) Intensive cultivation of yeast using amino acids.

e) Intensive cultivation of yeast using fatty acids and zinc.

3. The yeast metabolizes the sugar in the wort to alcohol, CO2 and energy. Which of the following sugars cannot be fermented completely by top-fermenting yeasts?

a) Glucose b) Maltose c) Sucrose d) Raffinose e) Fructose a) The fermentation takes place by mixed culture of top-fermenting yeast and lactic acid bacteria. b) During secondary fermentation, raspberry or woodruff syrup is added. c) Salt is added to the Weisse to round off its full-bodiedness. d) Berliner Weisse must be produced with 100 % wheat malt. e) Berliner Weiße is typically characterized by an intensive hop aroma. a) Boiling b) Addition of chlorine c) Irradiation by UV d) Addition of HCl e) Ozonation a) heated. b) cooled down. c) aerated. d) mixed with H2CO3 e) degassed.

4. In the recent years, the top-fermented Berliner Weisse has become very popular again. Which of the following statements about Berliner Weisse is correct?

5. Spring water from your own wells should be sterilized before being used as brewing water. Which of the following procedures is not suitable for the sterilization of brewing water?

6. After the water has been sterilized, further treatment steps often follow. In order to remove iron from the water, the water is...

7. The color and aroma substances in malt formed during kilning are largely socalled melanoidins. These melanoidins are formed from: a) Amino acids and sugars b) Dextrins and monosaccharides c) Caramelized simple sugars d) Caramelized oligosaccharides e) Coagulated protein a) A tendency of the finished bottled beer to become cloudy. b) Bursting of the filled and sealed glass bottles. c) Flocculation of the protein due to the influence of cold temperatures. d) Development of an aging flavor due to UV influence. e) Spontaneous foaming on opening the bottle. a) The color of the finished beer becomes darker. b) The CO2 binding capacity of the beer decreases. c) The filled beer tends to gushing. d) A sluggishly fermentation. e) The foam stability of the finished beer is reduced. a) The α -amylase breaks down the long starch chains into smaller units (dextrins). b) β -amylase always splits off two molecules of glucose (= maltose) from the ends of the starch chains. c) Both enzymes are insensitive up to temperatures of 100 °C. d) Both enzymes work optimally at specific temperatures and pH values

8. Gushing is a recurring quality defect in bottled beer. What is gushing?

9. Zinc is a trace element and is also of high relevance for the brewing process. What is the effect of too little zinc in the beer wort?

10. The enzymatic saccharification of starch during mashing is mainly carried out by α-amylase and β -amylase. Which statement is incorrect?

Answers

1. b) The term “yeast management” comprises all the yeast related processes and activities of a brewery. This begins with the selection and the care of the yeast strain in the laboratory, it includes the propagation in the brewery, the storage and ends with the recovery of beer from the surplus yeast and with the final disposal of the yeast itself.

2. b) The aim of yeast propagation is to produce pitching yeast with an active metabolism available in the shortest possible time under sterile conditions, which leads to a optimal fermentation and good beer quality. Essential factors are primarily: an appropriate temperature and the supply of oxygen, free amino acids, fatty acids, and trace elements.

3. d) One of the most significant physiological difference between top and bottom fermenting yeasts relate to the fermentation of the trisaccharide raffinose. Bottom fermenting yeasts can use raffinose completely because of their enzyme spectrum whereas top fermenting yeasts can ferment only a third or none of this trisaccharide.

4. a) Berliner Weisse is a naturally cloudy, pale beer with an original gravity of about 7.5 % made with 35-50 % wheat malt. It has an alcohol content of about 2.7-2.8 % by volume and a CO2 content of 0.7 %. Fermentation is performed with a mixed culture of top fermenting yeast and lactic acid bacteria. This makes the ’Weisse’ acidic at the end of fermentation with a pH value of 3.3 – 3.6.

5. d) The addition of HCl is not suitable for the degermination of water, since a lot of yeasts and bacteria are able to grow also at a low pH. In practice, brewing water is treated with active chlorine (max 1.2 mg/l), chlorine dioxide (max 0.4 mg/l) or ozone. Furthermore, the water can be sterilized by the application of UV irradiation or by sterile filtration.

6. c) Some of the ions dissolved in the brewing water – e.g. iron and magnesium – can precipitate and thus form deposits in the pipework or corrode it. They can be removed by aeration after deacidification. The salts are converted into an insoluble form, are precipitated and can removed by filtration.

7. a) At temperatures above 90°C and a longer exposure time, amino acids bind with sugars to form red-brown, aroma-intensive compounds, the melanoidins (the so-called Maillard reaction). The scale of the formation of the various compounds depends on the temperature, the duration of the heat exposure, the pH value, and the moisture content of the green malt during the kilning process.

8. e) Gushing means the sudden outflow and (sometimes) excessive foaming of beer on opening the bottle. This unsightly effect is a quality defect, and gives rise to customer complaints. Gushing is related among other things to mold formation on the brewing barley in damp harvest years.

9. d) Zinc is a trace element of great physiological importance for protein synthesis and cell growth. The fermentation proceeds slowly in case of zinc deficiency, yeast propagation is retarded, and the reduction of diacetyl is incomplete. Only about 20 % of the zinc in the malt goes into solution during mashing in. If a threshold of 0.10 – 0.15 mg zinc/l is not reached, the aforementioned fermentation difficulties may occur.

10. c) This statement is not correct! The α -amylase acts optimally at 70-74°C and is rapidly destroyed at 80°C. The optimum pH value is 5.6-5.8. The β-amylase acts optimally at 62 °C (59- 63°C) and is very sensitive to higher temperatures. At just 65°C it is inactivated relatively quickly. The optimum pH value is 5.4-5.5.

Planting trees as a symbol for a strong partnership between VLB Berlin and the South American brewing industry