- Scratches and/or black discolouration inside a can.
Fruit acid in the concentrated grape juice will eventually attack the metal of the can through tiny imperfections in the lacquer. Provided that
the can is not leaving, the contents are perfectly safe to use, and the amount of metal dissolved by the concentrated grape juice is negligible. However, do not store cans too long, as the flavour loses
freshness and the colour can darken. It is much better to store finished wine!
- Crystals in the can.
Grape sugar and/or cream of tartar may settle out of the compound in the can, particularly after storage in the cold. This has no effect whatsoever on the quality of the finished
wine, but it is important that all the deposit is thoroughly mixed into the must before adding the yeast.
- Concentrate is too dark.
Compounds to make white wine are amber in colour, and may even appear red. Dilute the compound according to the instruction before making a final judgement. See also Finished wine is too dark.
- Must (liquid) is too dark.
White wines made from all juice compounds may be a little darker than their commercial counterparts. This is a result of the concentrating and packing process. It does not
usually detract from the finished wine.
Occasionally this could arise when a very old can (2 years old or more) or one which has been stored in a warm room is used. The concentrate in these cans will
probably be quite dark, however it is quite wholesome and it will lighten during fermentation and clearing. The finished wine may be a little darker than usual, but it could be blended with something paler if
desired. Cans generally should not be kept for too long periods, as the fresher product yields the better results.
- The must (liquid) turns black or green.
This is caused by adding yeast nutrient. There is no need to add yeast nutrient to many of the concentrated grape juices, although it is essential with Country
wines. Change in colour is quite harmless and it will return to normal once fermentation begins.