7. Brewing And Fermentation Flashcards
Name the three processes of malting and explain the processes in each
The malting process uses the seeds own machinery to turn starch to simple sugars.
- Grain is soaked in water until increased in weight by around 50%
- Water is removed and grain is left to germinate (turned constantly during this process)
- malting continues until acrospire is 75-100% the length of the grain
- Modified gain is dried
- temperature and length of time varies with type of malt (lower temps given to pale malts
- malt is dried until desired colour is reached
- malt is moved constantly so roots and acrospire drops off
What is the process of mash? Describe what happens to complex polysaccharides if mash time is shortened or lengthened
Mash is used to convert complex carbohydrates into simple sugars.
- the longer the mash time the more carbohydrates are broken down
- long mash can also lead to astringent tannins being extracted
How does the changing of the temperature of mash alter which enzymes are active in breaking apart complex carbohydrates?
- Mash conducted between 63-69 degrees Celsius
- alpha amylase breaks large chain into small non fermentable 68-75 degree Celsius
- beta amylase break single maltose of larger chains 54-65 degree Celsius
Why is the water quality an important factor during mash?
- Balance of all the minerals is important
- high bicarbonate raises alkalinity
- dissolved minerals accentuate malt flavours
- high sulphites increases hop bitterness
What are hops and why are they used in making beer
Hops are the seed cones of humbles lupulus and are a major bittering compound for beer. When brewers need to extract bitterness they add hops during the kettle boil to release the bitter qualities.
How does changing pitching rates affect the beer that is produced
The increase in doses of yeast pitching rates (high cell density) allows for an increase in the productivity of fermentation. However it also requires an increase in the amount of yeast biomass produced and therefore beer extract losses are increased.
What by products do yeast add to beer (other than alcohol)
Esters, carbon dioxide and fruity esters.
Why is cooling of the wort necessary
Wort is cooled as quickly as possible to stop isomerisation, to stop mallard reaction and to reduce loss of volatile flavour compounds.
Yeast pitching will alter the type of beer that is produced during fermentation. State the types of beer that low and high rates of yeast pitching result in
Ale = 0.75 billion cells Lager = 1.5 billion cells
Higher alcohols produced during fermentation result from keto acids. How can the amount of higher alcohols be altered?
By adding more sugar, the yeast eats the sugar and that produces more alcohol.
Most brewers use dry malt extract as their sugar source because it will add more alcohol to the beer but doesn’t add a lot of sweetness
How are esters produced in beer and what role do they play?
Esters give the fruity/flowery aroma
- are produced via the reaction between alcohol and a fatty acrylic-coenzyme A - reduce production by high pressure, low temperature, low free amino nitrogen and high aeration
How can levels of esters be altered in beer?
By controlling the fermentation temperature.
- higher temperatures in fermentation result in rapid yeast growth, more AAT = more ester
How are ‘low carb’ beers made?
- they simply use more flaked corn or rice syrup in the mash. Normal malted barley leaves behind a lot of un-fermentable sugars which are what contribute to the carb content of beer whereas corn/rice ferment more completely so the result is less residual carbs
Why are glycol jackets used to control temperature during the fermentation process?
- they maintain the correct temp
- maintains the optimum temperature for type of beer
- glycol can hold heat longer than water resulting in an increased efficiency, it also has antifreeze properties so it can be cooled to subzero temperatures without freezing and clogging anything.
