Fermenting a wort into a beer could be considered easy but is often challenging as well. Nowadays, adding dry yeast to a wort is very simple; especially with the Fermentis’ E2U direct pitch concept, giving you the confidence that the yeast will do its work to create your intended beer. Indeed, yeast has only one goal: grow and survive. It’s the Master Brewer, with his knowledge and experience, who has the responsibility to drive the yeast in the right direction to produce the beer of your dreams. With a few simple adjustments, fermenting wort into a quality beer can be greatly improved.
Here is our top 5 ways to improve fermentation
1. Use an appropriate pitching rate:
It’s commonly a brewer’s belief that yeast can be used with a lower pitching rate than recommended. Using the right pitching rate is a key leverage for a brewer to steer the yeast in the right direction.
Using a low pitching rate can lead to several undesired consequences. Firstly, the probability of having a slow and long fermentation is greatly increased. In addition, some off-flavours are typical with long fermentation. To list only two: diacetyl and acetaldehyde (green apple flavour) are two major off-flavours.
Using a low pitch rate will also add stress to the yeast. This can lead to shift in aroma profile (the level being dependant on the yeast strain) and even off-flavours like H2S (rotten egg).
Using a low pitch rate will allow the yeast to produce more biomass. Therefore, yeast will use a part of sugar to make biomass ”rather than beer”. On top of that, it will increase genetic deviation, with a significant risk to decrease the overall quality of harvested yeast.
Using the right amount of dry yeast will give the beer improved conditions, the brewer the best possible result and a beer to be proud of.
2. Understand Oxygen management:
Beer yeast (top or bottom fermentation) can synthesize most of its key components using energy and basic nutrients. For example, yeast has the ability to make all the amino acids required for its growth providing there is ammonium (NH4+) and energy source in the media (and SO4– if there is a sulphur).
Yet, some essential molecules can only be produced when yeast has access to oxygen. Those compounds include ergosterol and unsaturated fatty acids. They are necessary molecules that ensure fluidity and permeability of the yeast membrane. With a deficiency, yeast has difficulties to grow and to import other mandatory molecules leading to insufficient growth and an incomplete fermentation.
Fermentis yeast is a dry version of a stressless yeast in its most active state. It contains a rather sufficient amount of reserve compounds including but not limited to ergosterol and unsaturated fatty acids. Therefore, if you use Fermentis yeast at the recommended pitching rate (based on the full volume of wort), there is no need to add oxygen or air. On the other hand, adding air/oxygen is mandatory with “darauflassen”, i.e. when you add multiple brews in one fermenter (and a lower pitch rate based on the full volume of wort), or if you make a high gravity beer (> 16 to 18 °P).
3. Optimise temperature management:
Temperature plays a big role during fermentation. Beyond fermentation efficiency, it is important to consider the effect temperature management has on your final beer.
Putting aside any aromatic characteristics, all yeasts ferment better at the higher end of the temperature range they’ll work under. It’s the brewer who has the responsibility to choose the right temperature to steer the yeast towards the targeted flavour profile. Here are some guidelines from the brewing experts at Fermentis coming from years of experience.
For ale beers (produced with top fermentation yeasts), a temperature between 20 and 24 °C is most of the time ideal. Below 20 °C you risk the probability of a long fermentation (along with the same issues as observed regarding pitching rate). Fermenting above 24 °C increases your chances of producing off-flavours like H2S. One of the exceptions to the rule is SafBrew™ HA‑18 (a mix between yeast and enzyme) which will deliver a nice aroma profile up to 35 °C.
For most lagers and pilsners (produced with bottom fermentation yeasts), we advise a temperature of 11-14 °C. The lowest temperature we could suggest would be to make a Bohemian style Pilsner with SafLager™ S‑23 down to 9°C. One of the exceptions here is SafLager™ W‑34/70. This so called “German Stone”, originating from the great Weihenstephan Brewery, will give a neutral and refreshing profile even when fermentied at up to 20 °C.
Pitching or hydration temperature should be as close as possible to the fermentation temperature.
4. Limit Attenuation Test:.
Even with a same recipe, the apparent degree of fermentation (ADF) may vary from one fermentation to another. The reason for this variation can be multiple, and include raw material characteristics, mashing process diagram, fermentation management and yeast vitality. There is a very useful way to determine whether the variation is due to the mashing or fermentation management, i.e. through Limit Attenuation (LA).
Conducting a Limit Attenuation Test consists in using some cold wort and add an excess of yeast (11 g in 200ml) to it. After 48 h of fermentation at 20 °C under constant slow agitation, comparing apparent extract (AE) in real conditions (in the fermenter) to apparent extract in limit attenuation (LA) gives a very good indication.
When the ADF is lower than usual and you have a 0.2°P of difference between AE and LA, the process before fermentation should be looked into (raw material and mashing).
When you have a significative difference between AE and LA, e.g. 0.5°P, the fermentation process should be looked into.
5. The beer flavour comes from the whole production process:
Decisions the brewer make regarding mashing often have consequences for the final beer. Being aware of this will greatly help to improve the beer flavour. For example, a sulphury aroma of cooked vegetable or corn in the final beer comes from a compound called DMS (dimethyl sulphide).
It is commonly mistaken for H2S, another very common sulphury flavour. DMS comes usually from a lack of boiling (time or evaporation) or from a prolonged whirlpool stage.