Check your expert knowledge

How good is your expert knowledge when it comes to beer brewing? Whether craftsmanship or extensive expertise in the field of microbiology and raw materials: A brewer needs the knowledge and overview of the manufacturing process. Therefore, the questions cover a broad range of facts which a professional brewer should be familiar with.

1. In order to convert the α-acids from the hops into the bitter tasting iso-α-acids, you need

a) high temperatures b) low temperatures c) a pH below 4.5 d) a surplus of zinc in the wort

2. When do we talk about dry hopping? When adding hops

a) into the first wort b) during wort boiling c) into the whirlpool d) in the storage tank

3. Which hop component is not relevant for brewing purposes?

a) Bitter acids b) Hop oils c) Lupulin d) Cellulose

4. Which important enzyme is not available in the raw barley kernel and is formed during the malting process?

a) α-amylase b) Peptidases c) Exo-beta-glucanase d) β-amylase

5. Which is the optimal pH of the mash with regards to the enzyme activity?

a) 4.2 – 4.5 b) 4.6 – 4.8 c) 5.4 – 5.6 d) 7.0 – 8.0

6. How do yeast cells multiply?

a) By mating b) By cell division c) By cell budding d) By sporulation

7. During fermentation a couple of by-products are produced by the yeast. Which of the following substances are no fermentation by-products?

a) Aldehyde b) Leucin c) Ester d) Vicinale diketones

Photo: VLB Berlin/FIBW

8. What is the definition of a Pasteurization Unit?

a) Keeping a temperature of 100 °C for 100 seconds b) Keeping a temperature of 1 °C for 60 seconds c) Keeping a temperature of 100 °C for 1 hour d) Keeping a temperature of 60 °C for 60 seconds

9. Diacetyl is formed

a) during wort boiling b) during fermentation c) at the end of the mashing process d) by contamination by acetic acid bacteria

10. What is the major effect of beer stabilization by means of Polyvinylpolypyrrolidon (PVPP)?

a) The yeast cells are removed b) The proteins are removed c) The tannins are removed by adsortion d) The tannins are removed by chemical degradation

11. Dimethyl sulphide (DMS) is undesirable in wort because

a) it reduces the hop yield b) it causes an off-flavour (boiled vegetables) c) it reduces the fermenting power of the yeast d) it has a negative impact on the coagulable nitrogen

12. Which component contributes to the typical flavour of a Bavarian style wheat beer?

a) Diacetyl b) Buntandiol c) 4-vinyl guaiacol f) Ethanol

Answers

1. a) α-acids (also called humulones) are the most important hop compounds for the bittering of beer. They are initially insoluble in water and are isomerized (chemically converted) at the high temperatures during the wort boiling. They are transformed into soluble iso-α-acids which contributes to the bitterness in the finished beer. 2. d) Dry hopping means adding hops after cast-out. The basic idea is that the volatile additional hop oils cannot be driven out any more, so they can considerably influence the aroma of the beer. Adding the hops at the end of the fermentation or in the storage tank is the best and commonly used method. This is where the contact time is the longest and dissolution of the hop oils is better thanks to the alcohol that has already been formed. The method called dry hopping has been commonly used in England for 200 years. 3. d) Lupulin is a yellow, sticky powder, which is located inside the hop cones. It contains the hop oils and bitter acids, which are essential for beer brewing. The cellulose of the hop dry matter has no effect on the brewing process. 4. a) Amylases are starch degrading enzymes and are important for the degradation of starch to maltose during the mashing process. While β-amylase is already present in large amounts in ungerminated barley, the α-amylase is formed during the germination process in the malt house. 5. c) Because of the three-dimensional structures of enzymes, their activity is mainly dependent from temperature and pH. By mashing within a pH range of 5.5 –5.6, which can be regarded as the optimum pH range for both α-amylase and β-amylase, the extract content can be increased in comparison to that obtained at a higher pH value. 6. c) Yeasts normally reproduce by budding. This is why they are also known as budding fungi. During budding, a small bubble-like protuberance from the mother cell is formed into which part of the cytoplasm as well as a daughter nucleus, formed by division, passes and a complete daughter cell is formed. In some yeast strains the mother and daughter cells separate from one another completely. 7. b) While aldehyde, ester and vicinale diketones (diacetyl) are formed by the yeast during fermentation, leucine is an amino acid which is absorbed by the yeast cells. 8. d) Pasteurization means the killing of microorganisms in aqueous solution by heating. The exposure time required to kill the microorganisms’ falls as the temperature rises. But too much thermal treatment has a negative effect on the beer flavor. This time requirement is derived from the pasteurization unit (PU). One pasteurization unit is a temperature period of 1 min at 60°C.

9. b) Diacetyl is a substance with an intense odor and flavor. Above the threshold value it gives beer an unclean, sweetish to revolting taste, which in high concentration is responsible for the aroma of butter or pop-corn. Diacetyl and its precursors are formed by the yeast at the beginning of the fermentation. Later, this diacetyl is degraded by yeast. It is therefore a key figure for the maturation of the beer. 10. c) Pure PVPP is a white powder with a melting point of 220°C and considered a technical auxiliary substance in beer production. It bonds with (adsorbs) phenolic compounds (compounds containing tannins). The PVPP tannin complex is removed from the beer by filtration. It’s a (colloidal) stabilization measure to prevent the formation of haze in the filled beer and extend its shelf life.

11. d) Dimethyl sulfide (DMS) is a volatile sulfur compound that gives beer an odor referred to as ‘cabbagey’, ‘cooked vegetable’ or ‘cooked corn’. A precursor of DMS, S-methyl methionine (DMS-P) is formed during the malting process (germination). DMS should be evaporated during the wort boiling. 12. a) 4-vinyl guaiacol (clove aroma) ist one part of the typical wheat beer aroma. It is produced by wheat beer yeast strains as fermentation by-product. Our recommendation: All you need to know about professional beer brewing – Textbook, 6th completely revised English edition (June 2019) By Wolfgang Kunze and Olaf Hendel (Editor) ISBN 978-3-921690-87-1