Do you pour the yeast sediment from the bottle or not?

The sediment at the bottom of a refermented beer is yeast that has done its work and then sunk to the bottom.

Brewers add sugar and yeast at bottling. In the closed bottle that yeast converts the sugar into carbon dioxide and a little alcohol. After that the yeast flocculates and settles out. What you see is therefore not contamination and not spoilage, but the remainder of a second fermentation in the bottle itself.

In the trade literature this is called bottle conditioning, in Dutch hergisting op fles.

With a hefeweizen the yeast sediment belongs in the glass, because the word hefe means yeast and the cloudiness is part of the style.

The German weizen tradition first pours out the clear part, leaves a little in the bottle, swirls it around and then pours it on top. That way the yeast gets into the glass evenly instead of in a lump at the end.

The style guidelines describe weissbier as cloudy from wheat and yeast, with the note that the sediment may settle at the bottom of the bottle.

With a tripel, dubbel or quadrupel, leave the last layer in the bottle, because there the yeast makes the beer cloudy and gritty instead of fuller.

Stronger beers take more yeast cells into the bottle at bottling. Research on bottle refermentation cites about 100,000 cells per millilitre for light beers and about 500,000 cells per millilitre for beers above seven percent alcohol. More cells means more sediment.

So pour in one smooth motion and stop as soon as the sediment in the neck of the bottle starts to move along.

Stand the bottle upright in a cool place for a day, then pour in one go until the sediment reaches the shoulder of the bottle and then stop.

Three things help. A bottle that has not just been transported. A glass that you first hold at an angle and set upright halfway. And a movement without tipping back, because every tip back swirls the sediment up again.

Warm beer foams more and pulls the sediment up with it, so pour at cellar temperature.

Yeast sediment says nothing about the age of a beer, because it forms within about two weeks of bottling.

The saturation phase of a bottle refermentation lasts about fourteen days. In that period the yeast multiplies, makes carbon dioxide and then settles out. A bottle that has just come from the brewery therefore already has a little sediment.

What does change with the years is the flavour, because yeast cells eventually break down. Whether that is a gain or a loss depends on the style.