It's elemental: Potato after-cooking darkening may be affected by nutrients

April 16, 2010
Researchers tested two potato cultivars to predict the occurrence of after-cooking darkening. Credit: Photo by Kris Pruski

Irish potato, one of the world's major food crops, is increasingly grown and processed for use in various products; consider the popularity of consumer favorites like French fries and potato chips. In the closely scrutinized food production industry, products are accepted or rejected on the basis of color and appearance, among other attributes. Quality defects such as after-cooking darkening, or ACD -- a change in potato's normal flesh color to gray, blue, purple, or black -- can affect the marketability of potatoes for both processing and fresh markets. With the current expansion of the potato-processing industry around the world comes a renewed interest in finding innovative methods to prevent ACD.

After-cooking darkening occurs when potatoes are exposed to air after cooking, including boiling, baking, frying, or dehydration. ACD has been reported from every potato-growing area in the world and is one of the most widespread, undesirable traits for potatoes and other tubers, even though it does not affect the flavor or of the crops. ACD is most common in boiled or steamed potatoes, but is also problematic in processed products such as oil-blanched , dehydrated potatoes, canned potatoes, prepeeled potatoes, and reconstituted dehydrated potatoes.

Researchers at Nova Scotia Agricultural College hypothesized that the concentration and distribution of elements in potato tubers could be used to predict after-cooking darkening. The objective of the study, published in a recent issue of HortScience, was to identify the elements (plant nutrients) whose content may relate to the severity of potato ACD. The researchers grew two common potato cultivars ('Shepody' and 'Russet Burbank') in three Eastern Canadian provinces for two seasons using various fertilization regimes. Fourteen elements were studied: phosphorus, calcium, magnesium, potassium, sulfur, iron, copper, sodium, zinc, boron, manganese, aluminum, silicon, and chlorine.

The "After Cooking Darkening" readings were found to be affected by fertilizer and a "cultivar-segment interaction". ACD readings were higher in tubers from fertilized plots compared with tubers from nonfertilized plots. The distribution of ACD was found to be similar in both cultivars studied, with the stem end being the darkest, the center segment being the lightest, and the flesh darkening again slightly toward the bud end. The elements most strongly correlated with ACD severity were phosphorus, calcium, copper, and magnesium. According to the researchers, the study provides a useful method to predict the severity of ACD, which could assist the processing industry in predicting the occurrence of ACD and in developing agronomic treatments to minimize it.

"This study demonstrated how information from element distribution can be used in predicting the occurrence of a tuber quality trait, specifically ACD", commented Dr. Gefu Wang-Pruski, corresponding author of the study.

The authors note that additional experiments to determine how tuber element content affects the change in ACD severity over time may make it possible to predict the severity of ACD in tubers in late stages of storage by determining the element concentrations and their spatial distribution of the same lot of tubers at harvest.

Explore further: Gene silencing used to make better potato

More information: The complete study and abstract are available on the ASHS HortScience electronic journal web site:

Related Stories

Spud origin controversy solved

May 15, 2007

Molecular studies recently revealed new genetic information concerning the long-disputed origin of the “European potato.” Scientists from the University of Wisconsin-Madison, the University of La Laguna, and the International ...

Iron and copper relationship is studied

July 24, 2007

U.S. scientists studying the relationship of iron and copper in the body have found when iron absorption by cells decreases, copper absorption increases.

Bacterium Identified as Potato Disease Culprit

October 14, 2009

( -- Studies tying a new species of Candidatus Liberibacter bacteria to zebra chip (ZC) disease in potato should speed efforts to better protect the tuber crop from costly outbreaks.

Tough New Spuds Take on Double Trouble

March 3, 2010

( -- Americans love potatoes, consuming about 130 pounds per person annually. But it's a wonder the spuds even make it to the dinner table, given the many fungal diseases that attack the tuber crop -- powdery ...

Recommended for you

'Hog-nosed rat' discovered in Indonesia

October 6, 2015

Museum of Natural Science Curator of Mammals Jake Esselstyn at Louisiana State University and his international collaborators have discovered a new genus and species on a remote, mountainous island in Indonesia. This new ...

Stress in adolescence prepares rats for future challenges

October 5, 2015

Rats exposed to frequent physical, social, and predatory stress during adolescence solved problems and foraged more efficiently under high-threat conditions in adulthood compared with rats that developed without stress, according ...

Most EU nations seek to bar GM crops

October 4, 2015

Nineteen of the 28 EU member states have applied to keep genetically modified crops out of all or part of their territory, the bloc's executive arm said Sunday, the deadline for opting out of new European legislation on GM ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.