barley to beer the science behind brewing . ingredients of beer barley (hordeum vulgare ) hops...

Barley to BeerThe Science Behind Brewing

Ingredients of Beer

• Barley (Hordeum vulgare )

• Hops (Humulus lupulus )

• Yeast (Saccharomyces cerevisiae)

• Water

Barley

• Barley is selected to have a high starch to protein ratio as protein causes cloudiness in beer

• Barley has been bred to have a small amount of husk as the husk contains tannins that taint the flavour of the beer

• 90% of the barley grown throughout the world (1980 figures) does not meet minimum standards and is therefore used for feed

Barley

Hops

Hops

Hops

Yeast

Processes

• Malting (7-9 days)

• Mashing (1-3 1hrs)

• Boiling and adding hops (around 1hr)

• Chilling

• Fermenting (2-8 weeks)

• Bottling / Kegging

• Conditioning (1 week – 2 years)

Malting

• The purpose of malting is to activate enzymes in the grain.

• The process of malting includes:– Germinating by wetting the grain until the ascospore

reaches aound 70% of the length of the grain – Drying in a kiln

• Around 80°C for light malts, 105°C for dark malts• Varying the humidity and temperature of the kiln changes the

malt flavour

Mashing

• Malted barley is added to water in a process called mashing

• The aim of mashing is to convert the starch in the malted barley into sugars using the enzymes activated by the malting process

• Sugars dissolve into the water to create a sweet malty liquid know to brewers as the ‘Wort’

• Different enzymes work at different temperatures and pH’s

• It is very important to have accurate control over the temperature of the mash

Enzymes in malted barley

Enzyme OptimumTemperatureRange

Working pH Range

Function

Phytase 30-52°C 5.0-5.5 Lowers the mash pH. No longer used.

Debranching (var.)

35-45°C 5.0-5.8 Solubilization of starches.

Beta Glucanase 35-45°C 4.5-5.5 Best gum breaking rest.

Peptidase 45-55°C 4.6-5.3 Produces Free Amino Nitrogen (FAN).

Protease 45-55°C 4.6-5.3 Breaks up large proteins that form haze.

Beta Amylase 55-66°C 5.0-5.5 Produces maltose.

Alpha Amylase 68-72°C 5.3-5.7 Produces a variety of sugars, including maltose.

Amylase at work

Starch + amylase + H2O

starch-amylase complex

maltose + starch + amylase + heat

• Amylase works by clipping off one maltose unit at a time from the large starch molecule. Thus starch is both a substrate and a product of the reaction.

Maltose

C12H22O11

A note on water

• The characteristics of water have defined the types of beer brewed in different parts of the world. A good example of this is Guinness brewed in Ireland. The water used to make Guinness is very hard and alkaline. Using dark malts reduces the alkalinity of the mash so that the enzymes are working in their optimal range.

Boiling

• Boiling the wort has 3 purposes:1. Steralize the beer

2. Denature proteins that otherwise make the beer cloudy. The proteins form clumps and drop out of the beer.

3. Add hops for bitterness, flavour and aroma

Adding hops

• There are many different varieties of hops available that each have their own unique flavour and bittering properties.

• There are two main categories of hops, these are:– Bittering (e.g. Pride of Ringwood)– Aromatic (e.g. Cascade, Saaz)

Bittering hops

• Hops contain alpha acids (a resin) that is made up of three closely related chemical compounds (humulone, cohumulone, and adhumulone)

• Bittering hops are added early to the boil to extract as much of the alpha acids as possible

International Bittering Units(IBU’s)

• IBU’s are a standard used to assess the bitterness of beer.

• IBU’s are calculated using the following formula:

• IBU's = ((Weight in ounces) x (%alpha acid) x (K)) / 7.25

Boil Time Constant (K)

45 min. to 60 min. K = 28 to 30

20 min. to 40 min. K = 8 to 12

O min. to 10 min K = 0 to 5

Aromatic Hops

• Contain essential oils that add a ‘hoppy’ flavour and aroma to the beer.

• The essential oils are volatile and therefore aromatic hops are only added at the end of the boil to avoid evaporation

Chilling

• After the boil the beer is chilled rapidly

• Chilling rapidly is desirable as it causes remaining undesired proteins to precipitate out of the beer preventing chill haze

Fermenting

• Yeast is added to the wort to convert the maltose into alcohol and CO2

• Yeast contains an enzyme called zymase which is the catalyst of this two step reaction

• The maltose is first converted to simple sugars, such as glucose, and then into ethanol and CO2

C12H22O11 2C6H12O6

C6H12O6 2CH3CH2OH + 2CO2

Lager vs Ale

• Yeasts can be broken down into two main categories these are– Top fermenting (Ale yeasts) and– Bottom fermenting (Lager yeasts)

Ale yeast

• Top fermenting

• Temperature of fermentation around 20°C

• Fermentation time approx 2-3 weeks – Eg. Coopers Pale Ale, Guinness, Cascade

Pale Ale, Traditional English Bitters

Lager yeast

• Bottom fermenting

• Temperature of fermentation around 10°C

• Fermentation time approx 4-8 weeks – Eg. VB, Tooheys New, Heineken,

Stella Artois, Pilsner Urquell

Bubbles

• There are two ways to get bubbles into beer– Using fermentation by adding a small amount

of sugar prior to bottling or kegging (e.g. Coopers)

– Pressurizing using bottled CO2 and a regulator (e.g. VB)

My Brewery

Mash Tun

Temperature controller

Heat the wort

Boiling Tun

Counterflow chiller

Culturing yeast

Fermenting