I’ve always called the effervescent in sparkling wine ‘the fizz’ but Professor Richard Marchal from Reims University whose whole working life is dedicated to assessing, counting, observing, photographing, monitoring bubbles in wine calls the mousse that forms a ‘collar’ at the top of the glass when poured, ‘the foam’, so the foam it is.
Frilling Foam Facts:
1. It is as yet unknown how to modify and influence the ascent of bubbles rising from the point of birth or nucleation point.
2. But the winemaker CAN influence the quality of the foam in the collar.
3. Healthy grapes = better foam. The base wine has to be good to have foaming properties – foamability (I kid you not, that’s the scientific term.) It can’t be instilled if it is not there in the first place.
4. Rot in grapes inhibits foam by releasing an enzyme which reduces the protein in the grape.
5. The more protein, the more foam.
6. Charcoal (used to stabilise colour) reduces foam because it affects the connection between protein and gas. Even more true of bentonite.
7. You need a rich colloidal structure in the wine to produce a good foam.
9. If the bubbles are small and tight as in higher quality sparkling wines, the foam is white. Bigger bubbles tend to make the collar grey or are not sustained to produce a collar at all.
10. Bubbles rise in the centre and move out to the rim at the top.
11. After three seconds quality bubbles decrease in size by 70%, but don’t burst, and form a perfect foam.
12. How much you pour into a glass affects the foam – right to the top of a tall glass and the bubbles have had a chance to increase too much in size and the foam is too frothy (think Guinness). A tasting portion does not allow the ascending bubbles to travel from the centre to the rim and no, or very little, collar develops. Half way up a glass is perfect.
13.You will have very few bubbles if your glass is perfectly clean. You need dust particles (no problem in my glasses!), or scratches, for bubbles to occur – gas is transferred from the bulk (wine) to the particles creating bubbles. This is the nucleation site.
14. Low alcohol produces more foam and becomes more like a forth.
15. Bubbles also carry aromas but there is less perception of them as it is mixed with CO2.
Right, enough science. I’m off for a glass of foam.