by Mark Allery » Sun Apr 13, 2008 9:32 pm
Hi Mike,
I can't claim to be an expert! But will help if I can.
First off on when to tap. Live trees will always leak some sap when you cut them, but its normally a slow seeping. At the start of the season when the buds start to swell, but well before the leaves start the tree increases the amount of sap moving up and down the tree and at the same time stored sugar is moved into the sap to move it to the growing points. For this period of a couple of weeks, the sap should pump strongly from the tree and have its maximum sugar content. When I get it right a demi-john will fill over just one or two nights.
Down south here this period is normally around middle to late march, you are right it will be later 'up north', but probably only by a couple of weeks. Having said that it seems that most people do their own thing time-wise and I am generally a little early.
From what I can gather the maximum sugar content of the sap is still quite weak and not enough to make a good wine unless you boil the sap down considerably. I generally add about 1 kilo of sugar per gallon plus the juice of a lemon (to add a little acid for the yeast to work). As you collected the sap over 3 weeks, it seems probable that you missed the surge of sap on this particular tree - I would think that the sugar content will be too low to ferment unless you have added some.
I use general purpose wine yeast, purely because birch sap wine is hard enough without the vagaries of air-borne yeast. Generally the air-borne yeast strains will be fairly weak and may not fully ferment the wine. The weak yeasts can then allow other bacteria to generate off flavours in the brew resulting in less predictable results and more complex tastes. Although I admit my knowledge here is mainly from the problems of using natural yeast in cider-making rather than wine.
Add some sugar, lemon juice and yeast and see what happens. Good luck - and don't get put off, if at first you don't succeed...........
cheers
Mark