Oxygenation of must in brewing

.The oxygenation in the initial phase of must preparation is the key to robust fermentation

Definition of terms: The novice brewers sometimes become a bit confused by this argument because they have been told not to introduce air into the finished beer. A part of the confusion undoubtedly derives from the use of the terms "must" and "beer" interchangeably, when in reality they are two distinct terms for the different ends of the beer production process. Oxygenation is very important in the must phase but it can ruin the finished beer.

The must refers to the state of prefermentation; beer refers to the post-fermentation malt beverage.

For the purposes of this article, aeration refers to the diffusion of air (the atmosphere contains about 21% oxygen in volume) in the refrigerated must, while the oxygenation refers to the diffusion of pure oxygen in the refrigerated must. Both methods of introducing oxygen will produce the same result: a healthy and active yeast population that will reward the brewer with a beer finished with clean tasting.

Why aerate your must? Most brewers learn early on that yeast needs a certain amount of oxygen to do their job quickly and completely; know when and why aerating, however, has confused many novice brewers. Let's take a look at why oxygen is needed and when to add it.

Because aeration is important

- The must boiled postboil is essentially free of oxygen.

- Oxygen in the early stages of fermentation promotes the health and reproduction of cells.

- Yeasts that have weak cell walls due to lack of oxygen during development can not survive the necessary repetitive budding that produces optimal yeast populations.

- Oxygen is necessary for the creation of sterols, an important factor in the development of the yeast cell membrane and other cellular components; this cellular development plays a fundamental role in the ability of the yeast to metabolize the sugars of the must in alcohol and carbon dioxide without contributing with aromas or odors.

- The presence of oxygen in the initial phase of fermentation reduces to a minimum the production of aromas and bad smells caused by esters and other by-products.

A strong cell membrane increases the yeast's alcohol tolerance, which is especially important with high-gravity bites.

The wasted postboil must is essentially oxygen-free, so something must be done first to remedy this. Yeast needs oxygen in the early stages of the fermentation process (aerobic phase) to promote cell health and teping. For most yeast strains, a dissolved oxygen level of 8 ppm is optimal and this degree of aeration is usually achievable. Fortunately, 8 ppm also coincides with the upper limit for must saturation, so there is little danger of overdoing it (more on this later).

This level of dissolved oxygen is important not only for fermentation, but also for the preparation of yeast starters. Although probably this week you will not begin to grow your yeast, it will suffice to say that yeast needs oxygen during the initial phase of activity, regardless of the specific application.

Knowing when to aerate: the fresher the must, the better the consumption of oxygen. If the postboil is aerated while it is still hot, the side effects of the hot side ventilation will no doubt appear in the finished beer, causing rapid cooling.

Although it is sometimes difficult to determine exactly when the sauté must is cool enough to aerate, it is reasonable to assume that the introduction of air or oxygen after the must has cooled to less than 70 ° F (21 ° C) will give very satisfactory results. .