The back label on a bottle of wit beer I bought instructed me to “gently rouse” the sediment before pouring. What and why is that?
Rousing is the technique of swirling a bottle to stir up solids so that they mix in with the rest of the liquid. This is considered de rigueur in the case of wheat beers, most classically Belgian wits and German hefeweizens, which tend to be bottled without recourse to filtration. Made up of yeast and protein, the hazy deposit contributes much of the spicy notes and wheat flavour of those styles.
A common technique is to pour about three-quarters of the bottle into your glass, then to hold the bottle by the neck in an upright position and swirl the base before tipping the hazy remainder into your glass. Alternatively, you could just shake up the bottle before opening, but this could overly agitate the carbon dioxide, resulting in a lava flow of foam.