Chemical composition
The chemical composition of the potato is determined by: variety, growing conditions (duration) and storage.
DRY MATTER CONTENT
Variety
Varieties differ in their chemical composition.
VARIETY: DRY MATTER AND YIELD
It is especially the dry matter content and sugar content that determines for which purpose potatoes can be used: fresh consumption, processing in potato products or starch production.
For processing (frying) potatoes should have high dry matter and low reducing sugar.
Changes of the chemical composition during growth
During the growing season the chemical composition gradually changes. At the beginning of the growing season the dry matter content is low and the sugar content is high. Towards maturity dry matter increases and sugar content drops. For that reason it is important that crops that will be processed are not harvested before they have matured. Besides it is important that crops are growing uniform. This to promote that all tubers are of the same age and have same uniform quality.
Maturity: dry matter-sugar
DRY MATTER & UNDER WATER WEIGHT---REDUCING SUGARS---GLYCOALKALOIDS
Storage
During storage, starch is converted into sugar and vice versa. Conversions are processes controlled by enzymes. These processes are greatly affected by temperature. Sugars are also used in the respiration process. This reaction is controlled by temperature. An example of the sugar balance shows that during storage at temperature of 6 oC or lower there is an accumulation of sugar.
Sugar changes during storage
Potatoes to be used for processing (high sugar content is not desired) are stored at a temperature of more than 6 oC
Processing
The method of processing determines to a great extend the composition of the tubers.
