Beer part 2: Mashing Flashcards
What is the aim of mashing?
- To convert starches in the malt to fermentable sugars (also some to amino acids in solution for yeast nutrients)
- To recover as much of the sugar as possible in the required volume of liquid.
- Flavour and colour extraction from the malts.
How many polymers does starch have?
2
Amylose fraction and an amylopectin fraction
What does mashing do?
Completes the conversion of starch and extraction of fermentable sugars - control is vital to the brewing process
In mashing what is starch converted to and what do the enzymes do?
Converted to sugar by alpha and beta amylase enzymes
- These act on the remaining shorter chain starches left from malting.
- alpha amylase: attacks 1-4 alpha linkages at random but doesn’t break these linkages close to a 1-6 branch point.
- Beta amylase: attacks penultimate 1-4 links in the chain only, doesn’t attack the 1-6 linkages. Works from nonreducing end (end capable of forming open chain)
Summarise the mashing process
- Malt ground to grist and fed to the mash tun.
- Hot liquor(water - composition important) is mixed in (using paddle)
- Traditionally an infusion mash and involves soaking the malt in water at 66 C for 1.5-2 hrs. Water will be recirculated to ensure the sugar is removed from barley as efficiently as possible.
- Need to determine temp and pH of mash
- Different techniques for lager and wheat beer
- Mash tun = what you mash in
What do enzymes do in the mash and what do each of the amylase enzymes do?
- Used to break down starches
- they break down different glycosidic linkages in the starch molecules
- Each enzyme performs under different conditions
Why are mash conditions controlled?
- To give the required wort e.g. select a specific enzyme to predominate and control the nature of the final beer
What leads to a faster conversion during the mash?
The amylases working together
What can alter the sugar ratios?
Temperature of the mash
What happens to amylose during mashing?
Reduced to maltose and the straight chain parts of amylopectin to maltose
What are amylases and how are they significant in brewing?
Present in saliva to break down starch, traditionally home-brewers would chew on grain and add that to mash.
What are alpha and beta limit dextrin’s and what effect do they have on the mash?
1-6 linkages of amylopectin are not broken, these are the residues of the branched regions.
They are unfermentable and alter flavour.
What are the enzyme conditions needed for mashing and why?
Compromise temp and pH needed to favour both alpha and beta amylase - 66C and pH 5.3.
Deviations will favour one over the other and result in different sugar concentrations
What would happen in terms of enzymes and final beer product if a mash was done at 70C (above compromise temp)?
- Little b amylase action
- Mainly alpha maltose action and random attack
- Main product = long chain sugars or short starches and alpha-limit dextrin’s
- large sugars = slow to ferment = remain in final beer = full-bodied sweeter beer
SO
Higher than compromise temperature would be ok for stronger cask ales - longer maturing, lasts longer
What would happen in terms of enzymes and final beer product if a mash was done at 60C (below compromise temp)?
-Little a amylase activity
- Mostly b amylase activity, attacking penultimate links
- so higher maltose levels
- Lower temp mash needs to be run for longer to get enough fermentables to get required alcoholic strength
- Mash products would be mostly glucose and maltose and some b-limit dextrin’s
-
SO
Beer = thin tasting but also quick maturing
How is pH effected during the mash?
- its a function of temp, so it will change with temp change
- Chemical composition of the water combined with the malts will effect pH the most so water is very important
What is the minimum calcium concentration of water needed for the mash?
50 mg/L
What does the water for mashing need?
Specific pH and mineral content
How can using water from the tap effect beer?
- it contains chlorine/chloramine/iron/bicarbonate which can have negative effect on beer flavour
What do chlorine and chloramine do to beer?
kill microorganisms including yeast
How can chloramine be removed from beer?
Using charcoal filtration or by adding campden tablets
Can be boiled off
What do campden tablets contain?
potassium/sodium metabisulphite
What can hard water do during mashing?
Cause scale on brewing equipment
- minerals are still needed as they are required for mashing process
How can water be softened and why?
- Using ion exchange resins or reverse osmosis
- Removes calcium and magnesium (reduce scale) and iron, manganese and copper = All negatively effect flavour
What are brewers tablets and why are they used?
- Added to get mineral and pH levels to the required level.
- Calcium sulphate/chloride/carbonate are all used to adjust pH and add calcium
What does adding lactic/phosphoric acid do?
Adjusts pH
What is maltase/a glucosidase and what is the optimum temp?
- Converts maltos to glucose
- 35C - 40C
- Can deoctation mash to get high glucose content worts
What is limit dextrinase and what does it do?
- debranching enzyme which catalyses the hydrolysis of alpha 1-6 glycosidic linkages (active at lower temps)
- only present in low amounts hence effect is negligible unless long mash periods are used and so a and b-limit dextrins are usually part of final wort
- residual sugar after mashing in part is determined by the limit dextrins
What are proteases?
- Act on protein and have lower optimum temps than amylase enzymes
What are glucanases?
- Break down glucans/gums
What determines which enzymes predominate?
Temp
Mashing steps
What step does traditional infusion mashing have?
Single rest step between 64 and 72 C
When can step mashing be used and what is it?
If the malt is a mixture/unmodified/ home malted
- mash is raised to specific rests to perform certain operations
What is an acid rest in step mashing?
Mash is rested around 35 C for up to 2 hrs.
- During this, phytase (present in malt) catalysed a reaction that lowers the mash pH
- Enzyme active between 30 and 45 C
What is the protein rest in step mashing?
Mash rested between 45 and 50 C
- used to degrade proteins/gums
- large proteins need to be removed but medium ones can stabilise beer foam and small ones needed by the yeast
- Enzymes responsible for degrading the proteins and gums are beta-glucanase, peptidase and proteinase.
- Activity temp overlaps at protein rest temp
What is saccharification in step mashing?
Mash is rested between 64 and 68 C
- to break down polysaccharides to sugars
- Alpha and Beta amylases are the enzymes needed for this
What causes beer hazes?
Biological
Non0biological
What are biological beer hazes caused by?
Bacteria and yeast
What are non-biological beer hazes caused by?
Amorphous or colloidal in nature
What is amorphous beer haze?
Caused by incomplete starch conversion (need to complete in mashing)
what is a colloidal beer haze?
Caused by interaction between hops and protein molecules, will occur in to enough protein is removed (can’t remove all though as yeast needs nitrogen source)
Colloidal hazes are referred to as chill hazes as present at 0C but disappear at 20C
What is decoction mashing?
Mashing with commercial lager malts
- contains more protein - can give chill hazes
- involves removing 1/3 of mash and heating it to the conversion temp, after which it’s boiled and returned to the mash.
When using a cereal adjunct, boil separately to rupture starch before adding
What does decoction mashing accomplish?
- Addition of the boiling decoction back to the mash raises it to the next rest temp
- Boiling process breaks up starch and protein molecules of the unconverted grist
- Produced a high degree of extraction from continental style malt
What is double decoction?
For malting with wheat malts
Decoction added after each rest step to raise temp to next rest
What do commercial enzymes do and give examples?
- exogenous enzymes can be added to ensure specific sugar and proteins mix in the wort (method for low alcohol beer)
- Thermamyl BrewQ contains alpha amylase
- Ceremix plus contains beta-glucanase, xylanase, alpha amylase and protease
- Ultraflo Max contains beta amylase and arabinoxylanase
What is lautering with regards to mashing?
- when mashing is complete, the liquor (sweet wort) is drained and collected for the next stage
- initial draining is recirculated as the initial filtering is poor
- Spent grains are retained during lautering and act as a filter bed - removing suspending matter.
- This filter is important as the aim is to get a bright, clear wart
What is sparging in terms of lautering?
- A lot of the sugar solution is stuck on in the malt grains
- This is displaced during sparging with water
- In a combined mash tun a rotating arm above tun sprays water over spent grains (lautering)
- In larger operations the completed mash is transferred to a lautering tun for the sparging - this frees up the mash tun for the next batch
What temperature is sparging at?
Water at 75-78 C is sprayed/poured over the mashed malt in the tun.
What happens to the sparge water?
It is continually drained and added to the seweet wort
When is sparging complete?
When gravity measure of the draining sparge liquor is less than 1.008-1.012
How long does sparging typically take?
1 hr
What is the aim of using a spray and hotter water?
To recover the maximum amount of sugar without diluting the wort too much
Why is sparge water hotter than the mash temp?
To aid the recovery of the sugars:
- by lowering the viscosity of the sugar solution
- by increasing the rate of leaching
- inactivates persisting enzymes
What is the overall aim of sparging?
to have max extraction of soluble fermentable sugars, colour, flavour; to obtain a bright wort with minimum suspended solids and to minimise dissolved oxygen in wort.
What is fly sparging?
Water is continually added at a slow rate and water level is kept just above the grains.
Most efficient but most difficult to set up for home brewers.
What is batch sparging?
Pre-determined amount of water is added over grains, lack of efficiency overcome by adding extra grain during blending
When is no sparge an option?
For thin small scale mashes - too much sugar lost otherwise
How is mash thickness altered?
- Higher solid/liquid ratios give increased enzymes in mash and faster starch conversion. Enzymes more heat tolerant when less water is present.
- Lower solid/liquid ratios give large volumes of dilute wort and requires conc. by boiling.
How are mash sparging time and temp altered?
- Limited due to making soluble undesireables (phenolics and tanins)
- Too much liquid will cause dilution
What happens to spent grains after mash?
- Spent grains still have high protein content (20%)
- Generally used for cattle feed as they contain nitrogen containing compounds they need
- also used in breads and cookies for human consumption
What are less used alternatives for spent grain?
- Composting (moisture level high so needs other streams)
- Anaerobic digestion (methane production)
- Landfill (only in urban breweries)
How does grain change during malting and mashing?
- Degradationof reserve substances, proteins around endosperm modified and transported, cell walls degrade changing physical characteristics, gums degraded
What mass of grain is lost during malting and mashing and why?
6-12%
Lost to production of roots and acrospires, and losses of co2 and h2o through respiration.
What % of sweet wort is oligosaccharides?
25-27%
What % of sweet wort is trisaccharides?
14%
What % of sweet wort od disaccharides?
maltose = 14% sucrose = 14%
What % of sweet wort is monosaccharides?
Glucose and fructose = 9-10%
Others = 16%
What happens to beta glucans in the composition fo sweet wort?
They need to be reduced as they increase viscosity and difficult for wort to run off - add industrial enzymes if not using gluconase rest step.
Summarise mashing (5)
- All grain beers are made of blend of malts
- Mashing is the step whereby the starches are converted to sugars by enzymes and the sugars are then dissolved into water to make wart - colours and flavours from malt are transferred to wort here.
- Mineral balance and pH of water used is important
- There is a specific temp and pH at which mashing need to be performed due to the enzymes, ‘the brewers window’.
- Follow mashing grains are sparged to ensure sugars have transferred.
