Now I bet very few of you have given this any thought. After all a rosé and a blanc de noir is a “white wine” made from red grapes. So you use your normal settling enzyme. However, this “white wine” contains a certain amount of anthocyanin, which means this anthocyanin should preferably remain a stable colour to ensure the longevity of the wine. In plain English, the wine should preferably remain pink or onion skin, whatever our style is, for a year or longer. It should not turn slightly brownish. In the absence of tannin from the grapes, or ellagic tannin from wood, or oxygen from micro-oxygenation, how does one stabilise this colour? Well for one; keep stuff that can de-stabilise it in the first place away from it.
Anthocyanin, like I said in a previous blog, is stabilised by sugar molecules. When the sugar molecules are removed the colour becomes unstable and can lose it red tinge and become, well, less red. I am not a specialist on polyphenols and bless the souls of the people who are because I find the topic extremely complicated. I have tried and tried to fully comprehend the colour / tannin chemistry in wine and I am not sure if it is lack of intelligence or sheer boredom with the topic that makes it impossible for me to fully grasp it. Anyway having gotten that of my chest, lets stick to the very simple model of anthocyanin and its sugar molecules.
Settling enzymes (white wine enzymes) can contain a side activity, formed by the fungus during production, called glycosidase. This activity is also known as “anthocyanase.” It removes sugar molecules from more complex structures. Although very positive for white wine aroma, it can also potentially remove the sugar molecules from anthocyanin. Now granted, you need a certain concentration to have an effect and some settling enzymes may not contain high enough amounts to cause any damage to your colour. It is nonetheless a good idea to clear this matter with your enzyme supplier to make sure that there will be no effect on your rosé colour. There are quality and composition differences between suppliers and it is a good idea to be aware of these differences. To make absolutely sure that you don’t have this activity in the enzyme you use for settling, use a red wine skin contact enzyme, where the supplier specifies: anthocyanase free, for settling of your rosé or blanc de noir juice. Skin contact enzymes contain the basic ingredients of settling enzymes as well as added side activities needed for skin pectin breakdown. So, it is a very effective settling enzyme as well, more expensive, due to the added activities, but very effective.