One way microbrewers make a distinction between themselves and mass produced commercial beers is that they insist they do not dilute malt flavours by using adjuncts (other sources of sugar apart from those derived from malt) and no preservatives are used.
While that may be true and it a common marketing theme, and a good one apparently, there is always a risk to the viability of the business. How so?
Firstly, by using the most expensive ingredients such as 100% malt it can reduce the profit margin, and to a point losses are experienced, especially if the shelf life of the beer is compromised and the beer doesn’t sell due to flavor changes.
And that brings me to the second point; that of using no preservatives. Because no preservatives are used there is an increased risk of staling and flavour tainting of the beer.
Beer stability is a complex issue and can take up a large amount of time just to cover the basics and so is not covered here.
Working at Fosters I spent 10 years in this area of stability and believe me it is still a raging issue with brewers worldwide. However, the basics are well established.
Oxygen is the main culprit but when oxygen gets in the beer and it experiences heat stress these combined conditions age the beer rapidly both visually and flavour wise.
Commercial brewers are able to limit the amount of oxygen ingressing into the beer but even so need to use oxygen scavengers, such as sulphur based ones.
Microbrewed beer can have poor shelf life due to an inordinate amount of oxygen but this may be the price the brewer is willing to pay in order to have full flavoured beer.
The only saving grace for the drinker is to go in search of the freshest sampling of the beer he has grown to like.