The bloom on the skin of most grapes and apples is yeast; there is no need to add extra yeast. For grapes, avoid breaking the seeds, which produce a bitter taste. Other fruits are best stewed in water. If sugar is available, boil 1 gal of fresh fruit in 1 gal of water, cool, use a colander or a press to extract the juice, and add yeast and 2 lb. of sugar. If sugar is not available, use half as much water in the fruit, let stand 12 hr, strain out the solids, and add yeast. When fermentation ceases, the cloudy-looking suspended yeast will settle out with long standing (6-60 d). A bitter taste in homemade wine is usually caused by tannin; a sour taste usually shows that some of the wine has turned to vinegar. For either condition, neutralize with hydrated lime. A full bottle of wine should not change to vinegar, but wine can be pasteurized by heating to 130-140 deg F for a few minutes; this temperature will not kill the one yeast strain that completes the fermentation.
A few people made wine from tomatoes: 3 lb. of brown sugar were added to each gal of juice, which was then fermented for 9 days.