Processing of RaspberriesAt the processing plant, the fruit is washed with gentle sprays of water and drained on a metal mesh belt. If the product is to be handled in the fresh state, it is placed in small, retail sized baskets usually with a cellophane over wrap and quickly cooled to 31 to 32 degrees F. In this condition, the fruit has a storage life only 5 – 7 days.
Some raspberries are frozen for the bakery trade and many for the manufacture of raspberry jam and jelly. To prepare them for freezing, the washed and drained berries may be placed in wooden barrels without sugar, and then placed in a room at 0 degree F or below and allowed to freeze slowly. Usually however, they are mixed with sugar (three parts fruits to one part sugar) then packed in slip cover cans of 50 Ib capacity. The covered fruit is allowed to freeze in cold rooms at 0 degree F or below.
In the manufacture of jam, the deforested fruit is passed through a pulper that allows essentially all the berries with the seeds to pass through the strainer. Sugar and water are then added the amount of sugar depending on whether the frozen product was packed with or without sugar. About 0.1 – 0.15% dispersed pectin is then added and the product is heated in open kettles to concentrate it to soluble solids content about 68%. Citric acid solution is then added to adjust the pH to 3.3 and the fruit is packed in glass jars and vacuum capped. The jars of product are then heated to bring the temperature of all parts to about 160 degree F after which the product is cooled.
Processing of Raspberries
