Issues In Fermentation. What Are They? Can They Be Fixed?

During a fermentation process, several problems and issues can arise. The most common is the failure to produce any product whatsoever. If it is a brewery, then lack of alcohol is the most problematic. The other issues are too long a fermentation or one that is just plain stuck which means the microbes/yeasts are not growing but maintaining a stable non-productive growth state. There is also an issue with producing not only the desired product but other compounds too. This makes fermentation heterogeneous and is complicated to sort out.

When it comes to yeast fermentation, they can restart or re-ferment, in the medium using the remaining substrates, having thought that the fermentation had finished. There may also be contamination with other microorganisms which cause secondary fermentation. A classic case in brewing is the production of acetic acid as in vinegar production or the production of lactic acid. This can also lead to the production of undesirable volatile esters which then triggers an unfavourable sensory response – sourness and off-beer.

Downstream processing must also be carefully managed. Inefficient or ineffective filtration procedures are commonly encountered. These produce off-flavours as a result. The yeasts or indeed any microorganism can remain in the final product causing not only off-flavours too but dangerous levels of carbon dioxide that have been known to cause glass bottles to shatter.

Ensuring the correct substrates are present. Some substrates will interfere with fermentation if they remain too long. Too much nitrogen will lead to strong rapid growth but skew metabolism into producing off-flavours.

Also, temperatures above 25°C for a yeast fermentation together with a higher concentration of sugars  such as glucose and fructose and other nutrients increase sugars’ consumption. On the other hand, lower temperatures which are less than 25 °C say and reduced nutrients’ concentrations are associated with final glucose and fructose concentrations higher than 3.5 and 10 g/L, respectively, which may promote the occurrence of undesirable re-fermentation.