Grape Juice

Grape juices contain about 10% carbohydrates in the form of sugars. As a juice, it is a considered a bland juice, thus it is a good feedstock for blending with other juices for making fruit drinks, carbonated beverages or as a sugar additive to grape musts for the fermentation of wines. Purified grape juice can be approached in a number of ways. Most often the target will be a white grape juice which is made via passing the clarified juice over a series of ion exchange resins to remove salts, organic acids and nitrogenous materials. The resultant juice feed may also be passed over an adsorbent resin or carbon bed to remove color and reduce any odors.

Figure 1 outlines how resins may be staged for the treatment of a grape juice feed stock. The strong acid cation resins are applied in the H⁺ form, the weak base resin in the free base form and the strong base anion resin in the Cl^- form.

The weak base anion resin is next applied to remove free acidity, organic acids, etc., and may also remove some color bodies depending upon the feed stock. At this point, the juice is fairly mineral free and some of the color bodies have been removed.

Depending how the juice is to be used, the feed stream could be taken for evaporation at this point or processed through an adsorbent resin or carbon bed to reduce color or odor components. For plant flexibility in handling a wider range of incoming juice feed streams, the process flow from the weak base resin is then passed through a strong base anion resin in the Cl^- form for color body removal followed by a second strong acid cation bed to pick-up nitrogenous materials that may have leaked through the other resin beds.

A final adsorbent polish is sometimes used with carbon or adsorbent resin. The de-mineralized, de-colored juice is then sent to an evaporator to concentrate the sugar content to that require of a blended juice.

Figure 1. Grape Juice