10-18-2011, 02:58 PM
It's highly unlikely that the yeast is the culprit (I have some thats been in the fridge for over 12 years and it still works fine). You might try using a starter. Pour about a cup of your juice (or room temperature water) into a separate bowl and add 1/2 cup of sugar and some yeast. Cover and let the yeast multiply, (several hours to a day) and then add back to what you want to ferment. This step isn't usually necessary, but it works well if fermentation is difficult to start for whatever reason.