ASBC_Fishbone_Vc.pdf

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DRIVERS OF BEER DRINKABILITY: YEAST

Yeast Esters & Higher Alcohols

Ethyl acetate:

fruity/

solvent/ 30 ppm threshold.

SAB:

inverse relationship between beer

"body" and [higher

alcohols].

Yeast Strain

"A tale of two yeasts, told

by an idiot, signifying

nothing”?

Ethyl acetate : ethanol ratio of

1:1800 minimum (+)

Isoamyl acetate:

banana/1.2 ppm threshold.

Normally the only ester in beer above threshold.

Phenylethyl acetate:

roses/3.8 ppm threshold.

Ethyl caproate:

apple/aniseed/0.21 ppm threshold.

Ester:higher alcohol ratios

of 0.30 or

over (+).

Esters

= ethyl acetate, isoamyl

acetate, isobutyl acetate, ethyl caproate

Higher alcohols

= n-propanol, isoamyl

alcohol.

.....all else constant (i.e. technology, raw

materials and process, lager beers

produced with Tuborg yeast have higher

ADFs, better E/A ratios, lower sulfur and

better drinkability.)

disproportional reliance on

Marketing to sell product.

Ethyl caprylate:

apple/0.9 ppm threshold.

Keep [higher alcohols] to < 90 ppm.

SAB:

inverse relationship between beer "drinkability"

and [acetaldehyde].

"Yeast Bite":

...harsh bitter imparted by

yeast autolysis.....peptides

are bitter in

character.

Beer

Drinkability

Lager beer spiked with ethanol increases dryness.

Keep [acetaldehyde] to < 5.0 ppm.

Acetaldehyde (-)

Methyl thioacetate (-).

[Glycerol]

.....contributes to beer

body

and

viscosity. Levels

in beer at 1-4 g/L level, NOT ppb or ppm!! Imparts

"sweet, viscous" mouth feel.

Flavor threshold is @ 10 g/L.

1970s survey of Canadian beers showed that beers spiked

with 5g/L were "milder" and lacked bitter aftertaste....at 20g/L

spiked beers much less preferred as too sweet. CHO

converted to glycerol by yeast is lost extract and changed

redox potential!!!! Nordstrom: "...to maintain intracellular redox

balance in a quickly anaerobic environment...yeast cells

reduce dihydroxyacetone to glycerol......biosynthesis of yeast

generates 6 mmoles of glycerol/1 gram dry matter yeast."

Thus, there is a correlation between yeast growth and

glycerol formation. In synthetic media, carbon balance

observed: 85.1, 6.3, 5.8 and 2.8% in ethanol, glycerol,

biomass and other by-products, respectively.

Other Yeast Volatiles

Yeast Solubles

ASBC No.Vc

(Casey;

June/05)

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