Cryo-SEM: frozen hydrated foam ("head") on beer
Foams are a mixed blessing to the brewing industry. During early stages of fermentation too much foam can be problematic. However, the form (or "head") in the final product is an essential aesthetic to many consumers of the product.
The best available method of examining foam at high resolution is by cryo-SEM, where the delicate structure is stabilised by freezing. Important information about bubble size, distribution and the changes in bubble shape during drainage can be derived from frozen hydrated preparations.
When the foam is fractured, often tiny fragments of shattered bubble wall fall onto the fracture surface. Larger fragments can be tapped off, but smaller pieces (marked by arrows) stick due to electrostatic attraction.
Bar: 200 µm (inset 100 µm)