Free-run juice is juice produced that flows freely from the skin of grapes before they are pressed. The natural weight of the grapes, when stacked on each other, tends to result in the release of some juice. Because it is not pressed with a presser, the juice contains much fewer tannins, and is thus less bitter. It’s sometimes called "the noble juice," and is more expensive because there is less of it, and it is considered higher in quality.
You may be able to buy free-run juice in natural foods stores, or you may have to order it on the Internet. It is very difficult to get, unless you are purchasing fermented juice in the form of wine. Winemakers may make a special or “select” wine from free-run juice. These are often some of the most highly priced of wines you will find, and normally, the red wines have a sweet fruity quality that is unlike standard red wines made from pressed grapes.
The French winemakers generally specify the types of wine made from noble juice. They are called vin de goutte. Wine made from pressed grapes is called vin de presse. Not all wines are specifically one or the other. Free-run juice and pressed juice may be combined, with the noble juice allowing for a reduction in tannins in the wine that are contained in the pressed juice.
Winemakers do try to eliminate some of the tannin, a natural protein occurring in the skins and seeds of grapes that is highly acidic. This may not always be beneficial. Though there are a few people who may be allergic to tannins, it is suggested that these acidic proteins may actually be beneficial to heart health. The “glass of red wine a day” prescription that doctors are now giving to some patients suggests that wine made from free-run juice may not be the best choice. In essence you need the tannins in order to get the cardiovascular benefits.
Still, too much tannin in wine or juice will cause it to taste very bitter. Thus most wine contains at least some free-run juice, and most juice does also. Pressing grapes to obtain juice is still more economically sound, since it yields much greater quantity of juice than that obtained by stacking grapes on top of each other, or macerating them, allowing them to soak in sugar or acids to suck juice from the fruit.