Storage for raspberries

Quality attributes generally considered by consumers in their selection and purchase of most fruits include: appearance, taste, smell, nutritional value, and absence of defects. Raspberries are extremely sensitive to handling and fungal attack, and thus it requires careful handling, harvesting, storage, and transportation.

Raspberries for long-distance shipping should be picked at the pink to light red stages, while fresh market berries can be picked at the red to dark red stages.

At 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 cellophane over wrap. Optimum storage conditions are 32 degrees F with 90 percent relative humidity. In this condition, the fruit has a storage life only 5 – 7 days.
Storage for raspberries

Mechanical drying of raisins

Grapes intended for dehydration are hand harvested and transported to the drying facility in pallet bins. In artificial drying, grapes are first dipped n 0.25 – 1 % lye (sodium hydroxide) solution at 200 – 212 degree F for 2 – 5 sec to remove a natural wax that impedes drying and to produce tiny cracks in the skin of the fruit in order to speed drying.

The fruit is then placed on trays and exposed to gaseous sulfur dioxide. This is to prevent enzymatic and nonenzymatic browning during drying. Hence instead of having the dark brown color of raisins that normally be expected, the raisins will be of a light yellow color when dried. The purpose of the pretreatment is to increase the permeability of the grape skin to moisture.

There are three main methods that are used for fruit drying: sun drying, shade drying and mechanical drying. Mechanical drying which is safe, rapid, and controllable is attractive to dry fruit production, especially when high throughput is needed.

Raisins are dried at temperatures not exceeding 165 degree F and at a low relative humidity. After the moisture content has been lowered to about 16 – 18%, the raisins are packaged in containers of various sizes to be sold at retail or for use by the food industry.
Mechanical drying of raisins