The Fermentation of Monosaccharides to make

Ethanol

Sandra ReynoldsUniversity Senior College

Dr Paul GrbinWine & Horticulture, University of Adelaide

“This material has been developed as a part of the Australian School Innovation in Science, Technology and Mathematics Project funded by the Australian Government Department of Education, Science and Training as a part of the Boosting Innovation in Science, Technology and Mathematics Teaching (BISTMT) Programme.”

The Fermentation of Monosaccharides to make

Ethanol

To make Ethanol Subtopic 5.3

“ETHANOL IS DERIVED BY FERMENTATION OF GLUCOSE WHICH CAN BE DERIVED BY HYDROLYSIS OF COMPLEX CARBOHYDRATES.”

Fermentation of Monosaccharides

The origins of wine-making arelost in history.

The earliest known beers were brewed6000 years ago in a country called Sumeron the plains between the Tigris and the Euphrateswhich is now part of Southern Iraq.

To pick grapes at the right pH is important

Too much makesthe wineundrinkable

Too little gives a flat taste

Crushing

Seeds & stems are removed

Grape juice is called must.

• Sulphur dioxide has been used in winemaking for 100’s of years to control the growth of unwanted microorganisms.

• Sodium sulphite, sodium hydrogen sulphite and sodium metabisulphite are used.

• A wrong yeast strain can produce an aroma described as wet horse blankets, cow manure and plastic bandages!

Skins are removed from the must for white wine.

The skins give the red colour to red wine!

C6H12O6(aq) 2CH3CH2OH + 2CO2

FERMENTATION of monosaccharides

using enzymes in yeast

Conditions1. Anaerobic2. Yeast to provide enzymes3. Warmth, 20 to 30 deg. C4. pH less than 75. Dilute aqueous

Saccharomyces cerevisiae – the yeast that provides our bread, wine and beer.

Magnification X 13,800

Skilled volumetric analysis determines theacid content ofwine.

Maturation gives rise to new flavour components by many chemical changes and by extraction from oak casks.

Fractional Distillation of Wine to Produce Spirits

•Fractional distillation of wine produces up to 96% ethanol

•Spirits contain 52% – 95% ethanol and these are not attacked by microbes.

•100% ethanol is called absolute alcohol – an excellent preservative!

Wine is Mostly Water & Has Poor Keeping Qualities

Australianbrandy isdoubledistilled

Cognac is triple distilled

Brandy & whisky are matured in oak casks.Colour and flavour components are extracted

Some 400 flavour components have been identified in whisky.

Copper rum pump and rum measures to dispense thedaily tot onthe Royal YachtBritannia until 1970when the rum issuewas discontinued.

Her Majesty’s proof spirit

Australian wine ready for drinking

Subtopic 5.3

“ETHANOL IS PRODUCED BY FERMENTATION OF GLUCOSE WHICH CAN BE DERIVED BY HYDROLYSIS OF COMPLEX CARBOHYDRATES.”

Beer Making

THE WORLD’S OLDEST RECIPE!WATER, MALT, HOPS, YEAST

• Beer is made by SOAKING malted barley with water, boiling it with hops; cooling it and then letting the whole lot ferment and mature.

• This process was used at least 6000 years ago in Iraq to make ale & bread.

To Make Ethanol in Beer

Wine is usually made from fruits. These contain simple sugars.

Beer is made from grain – barley is best. Grains contain starch.

Simple sugars are called MONOSACCHARIDES e.g. - Glucose (blood sugar, grape sugar) - Fructose, (fruit sugar) C6H12O6

Double sugars are called DISACCHARIDES E.g. - Maltose

- Sucrose- Lactose C12H22O11

Complex sugars are called POLYSACCHARIDES e.g.

- Starch(C6H10O5)n

Barley Contains Enzymes to Convert Starch into Fermentable Sugars

These are released when the grain is soaked in water & allowed to germinate for several days at 18oC.

This is called BARLEY MALT

The Sumerians baked this into barley bread.

Ground barley malt is soaked in water.

This revives the barley enzymes which break polysaccharides into disaccharide.

This reaction is called hydrolysis

(C6H10O5)n → C12H22O11

H2O

Boiling the Filtered Mixture Kill Germs & Deactivates

Enzymes

• Boiling extracts bitter resin from the hops & makes them soluble.

• Hops also act as a preservative

HYDROLYSIS

C12H22O11 + H2O → 2C6H12O6

OVERALL HYDROLYSIS

(C6H10O5)n + nH2O → nC6H12O6

FERMENTATION

C6H12O6 → 2C2H5OH + 2CO2

FermentationYeasts are added to the cooled wort

Note: Fermentation is an anaerobic process.

After maturing for several weeks at low several for several weeks at low temperatures, the amber liquid is filtered, ready for bottling or kegging.

Making distilled spirits:

The word comes from the latin ‘destillare’meaning ‘to drip’

The Fate of Alcohol is Vinegar ‘Acidic Wine’ ‘Vin Aigre’ F

• Acetobacter – bacteria that can use O2 to metabolise alcohol & extract energy from it.

CH3CH2OH + O2 → CH3COOH + H2O

• The ethanoic acid formed is a far more potent antimicrobial than ethanol .

• Vinegar came to be one of the most effective food preservatives of ancient and modern times.

Word List

CARBOHYDRATESSIMPLE SUGARDOUBLE SUGARCOMPLEX SUGARGLUCOSEFRUCTOSESUCROSEMALTOSESTARCH

POLYSACCHARIDEHYDROLYSISDISACCHARIDEHYDROLYSISMONOSACCHARIDEFERMENTATIONANAEROBICETHANOLAEROBICENZYMESETHANOIC ACID