How to reduce potato tuber discolouration
Discolouration or internal blackening or browning of potato tubers is responsible for significant post-harvest losses.
It is caused by the oxidation of phenolic substances, mainly tyrosine to melanin. Potassium, magnesium and boron can all have effects on discolouration and blackening.
Low potassium levels increase the risk of blackening
Potassium affects enzymatic blackening and after-cooking blackening and low levels of potassium can increase the incidence of after-cooking blackening.
Potassium influences the concentration of organic anions such as citric acid or ascorbic acid (i.e. vitamin C within the tuber). These 2 molecules have an antioxidative function, which decreases the incidence of enzymatic and non-enzymatic discolouration by slowing down the oxidation processes.
This trial from the USA shows the influence of potassium on enzymatic discolouration on two different varieties.
Magnesium levels linked to enzymatic blackening
Low magnesium levels can increase susceptibility to enzymatic discolouration.
This trial from the USA shows the influence of magnesium on enzymatic discolouration.
Boron reduces the incidence of tuber discolouration
Boron reduces the oxidation of phenols that are responsible for enzymatic discolouration. Thus, a good supply of boron reduces the occurrence of enzymatic discolouration in potato tubers.
Other crop management practices influencing potato tuber discolouration
- Selecting the right variety to meet production needs
- Taking care during harvest and grading to reduce physical damage and bruising
- Holding capabilities are present
- Irrigating to prevent, or minimise diseases such as common scab
- Harvesting in good conditions to avoid physical damage and disease infestation.
- Controlling temperatures and humidity in storage
Related articles
How to influence potato quality
There are three main criteria which define the quality of potato: tuber quality, skin finish and storage and cooking quality. A balanced crop nutrition program is important to help manage all of these criteria.
How to improve potato skin finish
Skin finish is important as consumers increasingly demand potatoes with clean, attractive skins. Tubers with surface infections of skin diseases are less attractive and also likely to have a reduced storage life.
How to reduce potato bruising
Potato tuber bruising is a serious problem in the potato industry. Correct nutrition of the crop prior to harvest can minimise the risk of bruising occurring with potassium, calcium and boron all having effects that reduce bruising.
How to reduce internal spotting in potatoes
Internal spotting of potato is a physiological internal disorder resulting in small brown spots appearing in the tuber. It is usually associated with either poor or interrupted supply of calcium to newly formed and expanding cells.
How to influence potato starch content and quality
Potatoes are one of the most important sources of starch worldwide. Variety choice is very important and potatoes with greater than 13% starch content are required in countries such as Germany. The higher the starch content, the lower the waste.
How to influence potato tuber dry matter content
Potato tubers with high dry matter tend to bruising more easily and disintegrate when boiled but have better fry colour when processed. Nitrogen, potassium and magnesium can all have influences on tuber dry matter content.
