Lesson 8 - Beer Properties End of Unit SAQ

** Your brewery has been asked by group head office to move to 50% high gravity brewing (wort gravity 50% higher than sales gravity).

           a. What effects could this have on beer foam?

           b. How can you counter these effects?

Response:

High gravity brewing (HGB) is achieved by:

• Producing a more concentrated wort in the brewhouse

• Fermenting and ageing the wort

• Dilution at filtration back to standard (sales) gravity (SG)

This brings efficiency, productivity, flexibility, and cost benefits. Generally, beer properties can be matched with SG brewing, except for foam stability.

HGB mashing does not extract foam protein as efficiently, and higher hydrophobic polypeptide losses occur proportionally in boiling, fermentation and maturation.

Yeast is subjected to increased stress in HGB due to increased osmotic pressure (gravity) and release the stress marker proteinase A, which slowly degrades foam protein.

This results is loss of foam stability once the HG beer is diluted and packaged.

To improve foam stability in HG brewed beers, without compromising other beer properties, we need to consider the entire process and introduce interventions such as:

• Adding some foam stabilising wheat malt to the recipe

• Avoiding low temperatures during mashing

• Using antifoam in fermentation to limit foam formation (foam generated during beer processing is lost forever)

• Good yeast management to limit proteinase A production

• Use of foam stabilisers at filtration, e.g. propylene glycol alginate or PGA