Ask Wine Wizard

I noticed an oily film on top of my Norton before I racked it. What should I be worried about and how do I fix it?

TroubleShooting

George Ritchie — Baltimore, Maryland asks,
Q

I’ve made Norton for a few years. This year I noticed an oily film on top before I racked. It smelled and tasted decent. What should I be worried about and how do I fix it? The acid is 0.95 and pH is 3.91. What should I do to lower the pH with out raising the acid?

A
Norton is a fun variety of red wine to make and certainly is a big favorite in the Midwest. I’ve tried some good Nortons over the years and I can share your worries over the wine’s high acid levels. However, before I get into that, let me address your first problem. It sounds like you had an infection of film yeast on top of your finished wine, which often (before the population gets too high and more noticeable) manifests itself as an oily plaque or film. These heterogeneous populations of yeast (undoubtedly with some bacteria mixed in) are aerophilic and therefore love to live on top of the surface of wine in storage containers, where there is air in the headspace of a carboy, barrel or tank. Though the wine may have smelled and tasted fine at the time, film yeast, if allowed to grow, can contribute spoilage aromas and flavors in finished wine, especially if they are allowed continued access to oxygen. Luckily film yeast are relatively easy to control. Your two best weapons against this kind of microbial
Response by Alison Crowe.