Science allows brewers to get the most out of beer brewing ingredients and processes, University of Otago food science lecturer Dr Graham Eyres says.
''This ultimately allows brewers to maximise quality and consistency, which will lead to greater consumer liking and commercial success.''
Eyers and colleague food science department head Prof Phil Bremer will explain some of the thinking behind this as part of Dunedin Craft Beer and Food Festival, which begins its week-long celebrations of the amber ale on Monday.
Science is something home brewer Max Major appreciates.
''I really like the science behind it. Understanding how it goes from a grain through different stages and ends up a beer.''
It hooked him into the hobby, as he enjoys experimenting with different combinations of hops, malt, yeast and brewing techniques.
The former University of Otago psychology PhD student, who began home brewing after being given a kit for a birthday, won last year's festival home brew competition with a sour beer called Wild Gose Chase.
It was his partner's dislike of beer but appreciation for sour beers that led him to give that type of brew a go.
So he did his research, found a recipe - Berliner Weisse - and split that main batch into little batches so he could try out some different types. He left one unchanged, dry hopped one with Nelson Sauvin hops, aged another on citrus fruits, and turned the last into the Gose by adding coriander and salt.
''It was quite enjoyable as it was a bit more involved than your standard IPAs, as it uses bacteria instead of yeast.''
As it required a higher temperature to ferment and he was brewing it in a Dunedin winter, he had to put a heater on and wrap it in blankets and a sleeping bag to keep it at the right temperature.
He liked the Gose, so thought he would enter it in the home brew competition.
It won and has been brewed commercially at Emersons as the official festival brew.
''I might hover around the tent to pick up on people's impressions.'
Major got to take part in the brewing process which opened his eyes to the sheer size of a commercial operation.
''The equipment is so much more massive. It was kind of cool to work on. The guys are super-knowledgeable and we got to talk beer and brewing.''
For Eyers, who researches hop flavours in beer and the factors that influence it, and Bremer, who is interested in the role of yeasts in brewing, that sort of appreciation is important, as many of the common mistakes and problems people have when brewing at home are related to science.
Eyers says the most common mistake home brewers make is poor yeast management, which leads to unhealthy yeast, abnormal fermentations and off flavours.
''Not adding enough healthy yeast is a common problem. Stressing the yeast cells by subjecting them to the wrong temperature can also result in them producing compounds which impact on beer flavour.''
It was also important to maintain hygiene standards and to store the beer appropriately.
''Beer should be fresh, at least for most beer styles.''
Bremer believes it is important for home brewers to find out from their council about the chemical composition of their water.
''Altering the water chemistry by adding brewing salts can have a dramatic impact on brewing.''
Natural waters contain varying levels of dissolved ions (magnesium, calcium and sulphate) and have varying buffering capacities (bicarbonate levels).
While softer waters (low levels of ions) favour the production of lagers and darker ales, harder waters (high levels of ions) favour the production of higher hopped, paler ales.
Home brewers can add brewing salts such as calcium sulphate, calcium chloride or magnesium sulphate to adjust the water chemistry.
Science helped brewers ''troubleshoot'' when things went wrong and explain why things happened.
''Brewing is also considered an art as well as a science; so you don't necessarily need to understand the science to make good beer,'' Eyers said.
For all grain (full mash) brewing, brewers need to understand the biochemical reactions and conversions that occurred during the process.
''It is important to understand the impact of mash temperature and water chemistry and how it influences enzyme reactions in the mash.
''That is the conversion of the starch in the malt into sugars that provide the substrate that the yeasts subsequently convert into ethanol.''
Bremer said they also needed to understand how mash temperature affected the activity of enzymes that break down protein and large polymeric substances that can cause turbidity and hazes in beer.
''Home brewers should understand the optimal temperature for the yeast strain they wish to use.''
At their ''Science of Beer'' talk, they will cover some of the common flavour defects in beer, such as diacetyl which is responsible for a buttery, butterscotch character which can be related to poor yeast management.
There were others such as acetaldehyde, which gives a green apple, solvent-like character, or dimethyl sulfide, which gives a cabbage, cooked vegetable character.
''A key concept that we will be discussing is that a flavour defect depends upon the beer style, where a particular flavour character (due to a chemical compound) may be desirable (or critical) in one style but considered a defect in another style.''
To see
Dunedin Craft Beer and Food Festival November 7-13, Science of beer, November 9, Ombrellos.
