During winter months there is often the appearance of dark purple or black areas on peppers, this can be both sweet and hot peppers. This can affect the appearance of the fruit to such an extent that fruit could be considered as unmarketable. It is, however, a normal phenomenon and can be beneficial if understood correctly.
 The discolouration is the results of anthocyanin, which scientifically can be described as a water-soluble polyphenolic pigment. Anthocyanins are a diverse class of flavonoids which are composed of an anthocyanidin backbone with sugar and acyl conjugates. Anthocyanin is found in many plant species including vegetables of which eggplant and pepper are the most obvious. They are responsible for the purple colour of these fruits. The anthocyanin content is dependent on the genetic makeup of the plant and is thus not present in all pepper varieties. This could have a big impact on the growers’ selection of a specific variety for his production programme. The different varieties could show either severe discolouration or no sign at all.Â
 The presence of the anthocyanin in plants is beneficial for the plant and also for health reasons. The presence of anthocyanin benefits the plants as they play a role in reproduction by attracting various pollinators and seed dispersers with the bright colour. They can also help to protect the plant against various biotic and abiotic stresses that the plants are exposed to. These plants could have a much better adaptation to climate change.Â
 Anthocyanin metabolism is affected by environmental conditions, but the molecular regulation of the effect is poorly understood. Various scientists are now exploring anthocyanin for its beneficial effect on plants and humans.Â
 The anthocyanin content of the fruit is highest when the fruit is still in the immature stage and decreases as ripening continues. In eggplant, the effect is clearly visible, as the commercial maturity of the product, meaning the fruit is harvested and used in the immature stage, is reached before the fruits are physiologically ripe. Anthocyanin accumulates in young immature vegetable tissue, especially sun-exposed sides of the fruit. This is to protect the plants from photoinhibition and photobleaching under high light intensities. Anthocyanins are photoprotective agents and can shade the plant tissue, thereby protecting the photosynthetic mechanism of the plant by absorbing the excess visible and UV light.
The presence of anthocyanin in the plant can also reduce the infestation of various insects and pathogens and display an enhanced tolerance to heat stress. Anthocyanin also plays a part in protecting the plant in low temperatures, even temperature leading to frost damage. Anthocyanins accumulate in the epidermal cells of the plant and decrease the osmotic potential of the cell and thereby delaying freezing damage. Although not scientifically proven yet, the darker discolouration of the plant parts, leaves and fruit, leads to higher temperatures and thus also protecting the plant, this could be beneficial especially in fruit to protect the seed, which is the offspring for the next generation.
Anthocyanin metabolism can be influenced by various environmental factors. Anthocyanin levels significantly increase during drought and high saline conditions, which could also be a way for the plant to protect itself. High light intensities irradiance, stimulate the anthocyanin metabolism and therefore it is more prevalent in the sun-exposed part of the fruit or plant. Low temperatures promote the biosynthesis of anthocyanin and high temperatures induce degradation. Light quality also affects the pigmentation – poor colour development is visible on fruit, which can be seen in eggplants grown in greenhouses with lower UV transmittance quality light. UV-A radiation increases the anthocyanin content of the plant.
 Anthocyanin is also acting as an antioxidant that prevents lipid peroxidation, helping to maintain membrane integrity and decelerate cell senescence, enhancing shelflife. The highest concentration of anthocyanins is found in unripened fruit and decrease as fruit ripen. This can be seen on pepper when the discolouration is clearly seen on green fruit and disappear on red mature fruit.
Although this phenomenon is seen quite frequently on pepper fruit and is often regarded as being very negative, the more studies being conducted on this, the better we will be able to understand and see the possible benefits to growers and how this can assist breeders in developing varieties that are better adapted to challenging environmental conditions.
Disclaimer
This information is based on observations and sources believed to be reliable. However, crop performance depends on the interaction of genetic potential, seed characteristics, and environmental factors, including management practices. Sakata Seed Southern Africa (Pty) Ltd provides no express or implied warranty for crop performance based on this information and accepts no liability for losses resulting from its use. Please refer to Sakata Seed Southern Africa’s Conditions of Sale before ordering seed.