Process description: Washing of fruits&vegetables
1. DESCRIPTION OF TECHNIQUES, METHODS AND EQUIPMENT (Heiss, R. [Hrsg]: Lebensmitteltechnologie)
First step after transporting fruit or vegetables to the plant is to clean and wash them because unwanted components such as leaf, dirt or earth should be removed. During cleaning process movements of raw material and dirt are changed by force effects so that separation of components is certified. The choice of cleaning technology depends on the type of raw material, the type of dirt and the following production process.
- Dry cleaning methods
Often used just for pre-treatment before the real cleaning process ca be started. Examples: riddle screens, magnet precipitator or air blower cleaner.
- Wet cleaning methods
Commonly water is used which acts as means of transport and as solving agent. Examples: wash baths with/without rotation of liquids, with/without movements of raw material, application of brushes….
Often several types of cleaning and washing processes are coupled in series. For example dry cleaning is used before wet cleaning for minimising the dirt load of the wastewater.
The rate of water consumption depends on different facts:
- Type, size and adjustment of washing machine
- Type and origin of raw material
- Further process steps
While using wash baths requires less water, cleaning with barrel washers is more water intensive. Also the surface of raw material influences the process parameters. Fruit and vegetables with rough surfaces require more intensive washing than these with smooth ones. High level of water consumption can also be noticed at washing products which have to be removed from pieces of plants or foul pieces. Another influence factor is the texture of the raw material, e.g. raspberries and strawberries can not be hosing by water. The harvest can be figured out in mechanical or manual way. From experience at mechanical harvest more leafs and spoilt fruit are expected than at manual one. If raw material is peeled from a full-washing can be abstaimed.
2. NEW TECHNOLOGIES