Stapletons Technical Bulletin:
Prune Juice Manufacturing Process

The basic ingredients for making prune juice are water and prunes. Prunes are the dried fruit of the prune plum. In California, most of the prunes are of the La Petite D'Agen variety, a prune plum native of Southwest France.

1. The prunes are washed and placed in a cooking tank along with the appropriate quantity of water.

2. The contents of the cook tank are then heated and stirred until the prunes mostly dissolve and the sugars go into the water to make juice. This can take from several hours to as much as a half a day (12 hours).

3. If viscosity reduction is required, enzyme is added at this point.

4. The juice is then strained or filtered to remove the pits and the un-dissolved solids.

5. The finished juice is then canned, bottled or made into prune juice concentrate.

6. For canning and bottling, the process is a hot fill and hold at 190°F.