How to Prevent Greening in Potato Tubers

Preventing and Addressing Potato Tuber Greening

 Greening is a primary cause of potato tuber quality degradation. Potato tubers are non-photosynthetic plant organs that lack photosynthetic equipment like subterranean stems. 

• The green color represents an increase in glycoalkaloids. Chlorophyll and solanine levels skyrocket as the potato turns green. 

• The presence of chlorophyll results in an unappealing look to customers, and an increase in solanine may pose a health risk. 

• Greening is caused by light exposure, which can occur in the field when potato tubers poke through the ground. 

• It can also occur in potato storage cellars, on shop shelves, and on the counter at home. Given that it may be an extensive marketing and retailing issue, how can greening be prevented or restricted?

reading also Potato cultivation in Egypt

Reasons for Green Potato Tubers

1. Various variables affect the greening of potato tubers in the field. When potato tubers emerge from the ground, they are exposed to light.                         
2. Thermal necrosis, a cavity in the pulp of a tuber caused by exposure to high temperatures, is often associated with light exposure in the field. Large portions of tubers can also turn green in the storeroom or even on store shelves when sold.                          
3. As a result, it is critical to maintain sufficient soil cover over the potato seed plot and a mound wide enough for new tubers to develop underground.                
4. Choose potato varieties that produce tubers planted deeper rather than shallow. However, the ridges should be tall if a shallow variety such as Russet Norkotah is grown. The usual guideline plant depth is six inches (15 cm).                                       
5. Although fertilization has no direct effect on solanine concentration, the impact of excessive and late nitrogen application on growth and maturation may increase solanine content.                                                                                                      
6. Solanine levels are more significant in immature and adult tubers. As a result, unless you planted early, don't worry too soon. Before harvesting, let the vines dry out and develop tubers.                                                                                                                           
7. The trapezoidal mound construction produces a broad, flat crop row. This allows new tubers to develop without protruding too far.                                                                               
8. Avoid planting on slopes where rows may be exposed to dry soil conditions and wind. Wind may erode or blow the row, exposing the seeds and reducing the size of the mound to cover new tubers. If erosion occurs early enough in the season and herbicide treatment allows, report the hill and rebuild the row.                                                                     
9. Drought does not affect greening per se, although it increases bloating and cracking of the ground. Excessive plowing should be avoided throughout the growing season. Tubers close to the surface may be exposed to light entering through cracks if the ground breaks near the end of the season.                                                                                     
10. Avoid letting the soil dry out, especially after the vines have dried out. In dry areas, it is recommended that irrigation be immediately done before drought. This will not only prevent ground cracks but also improve the effectiveness of chemical vine drying.                
11. When potato tubers are exposed to light, they turn green as a result of the presence of chlorophyll in them. This can be seen in the surface tubers in the soil and on tubers after harvesting and storage.                                                                                         
12. The greening process occurs concurrently with synthesizing the hazardous chemical solanine. Still, the two methods are distinct, with the greening occurring under yellow or red light and the toxic substance solanine forming under blue light.

Solanine is formed in a blue hue; normal light naturally contains all these colors.

(1) The process of producing chlorophyll

Chlorophyll is created in tubers within 2-4 days of light exposure, and it must be removed by placing them in total darkness for a month at a temperature of 23 °C. Chlorophyll is produced in the tuber's surface layer (approximately 2 mm thick).

The following factors influence the rate of tuber greening:

A-Variety: 

Kinds differ in their capacity to green quickly, with smooth white skin variants greening quicker than cork mesh skin varieties.

B. The maturity level of the tubers

Because the periderm layer is thin, the greenness of young tubers rises.

C- the amount of light, with the greenness increasing as the amount of light increases

D-Exposure to light for a given amount of time

After 14 hours of exposure to light of 70 feet/candle, the tubers turn somewhat green.

The look of greenness is greatly enhanced when the exposure duration is increased to 43 hours.

E- Temperature 

While the tubers are exposed to light, the rate of greening increases as the air temperature rises.

The ideal temperature for the production of chlorophyll is 20°C. It is incredibly uncommon and does not develop below 5°C.

(2) Solanine Formation

Solanine is a family of poisonous glycosides to humans and animals.

The tubers have a bitter flavor, and the presence of 15-20 mg/100 g of fresh tubers causes a bitter taste.

It's poisonous to consume, and solanine is naturally present in tubercles on the skin and around the eyes.

Specifically, if the ratio does not exceed 1.0-5.0 parts per million, the tubers are exposed to UV light.

Violet raises its solanine concentration multiple times, producing roughly 100 mg of solanine in humans.

This chemical causes severe digestive and neurological system diseases, as well as headaches. When exposed to light, tubers in their development stage, as well as newly harvested tubers, have a higher level of solanine than mature tubers. The greening of potato tubers might be a major issue.

FAQs: Greening of Potato Tubers

How does light exposure cause greening in potatoes?

Exposure to light triggers the production of chlorophyll, leading to greening. Storing potatoes in darkness prevents this reaction.

Can green potatoes be consumed safely after peeling?

While peeling removes the green layer, avoiding green potatoes is advisable due to potential glycoalkaloid content.

Do all potato varieties have the same susceptibility to greening?

No, susceptibility varies. Some varieties are more resistant to greening, making them a better choice for long-term storage.

Are there health risks associated with consuming green potatoes?

Yes, green potatoes may contain elevated levels of glycoalkaloids, which can be toxic. It's best to avoid consumption.

How can consumers prevent greening at home?

Store potatoes in a cool, dark place, away from direct sunlight, and consume them before the greening process occurs.

Do cooking methods affect the greening of potatoes?

While cooking can deactivate some glycoalkaloids, starting with non-green potatoes is essential for optimal safety.