The potato, whilst being one of the main staples of the modern Western diet, is usually most closely associated with a high fibre, starch and carbohydrate content. Green, leafy vegetables and fruits are understood to be better sources of other vital nutrients, including flavonoids and B vitamins.
But according to Roy Navarre, a plant geneticist at the USDA's Agricultural Research Service, this is a generalisation that does not hold true for all potato varieties. He has spent the last year investigating the nutrients in potato skin and flesh using high-throughput liquid chromatography and mass spectrometry.
Historically, potato-breeding programmes have centred around productivity and disease-resistance, rather than nutritional value. The same holds true for ingredients firms, who have focused on tapping potatoes' starch content.
However there are indications that the market could be receptive to value-added potato-derived products. For instance potato starch-centric Avebe this year formed a new subsidiary called Solanic, which aims to develop value-added ingredients from potatoes, such as high-performance protein.
The new ARS method enables sample analysis in just 12 minutes, and phenolic concentrations of 100 to 675 milligrams per 100 grams of dry weight can be detected.
The full results of the profiling are not yet publicly available, but the researchers have already analysed 100 wild and commercially-grown species and released a taster of their findings in this month's Agricultural Research magazine.
For instance, they report that phenolic levels in All Red and Norkotah potatoes were "especially high, rivalling those in broccoli, spinach and Brussels sprouts".
They have sought to expand knowledge on folic acid content in potatoes by looking at levels in some 70 varieties. Until now, only six varieties had been investigated, but the wider sampling has shown that levels can vary as much as three-fold.
"We looked at the expression of four genes involved in folate metabolism to see whether we can determine why one variety has more of this compound than another," said Navarre.
They have also found that flavonoid levels in potatoes can vary 30 fold between the lowest and the highest specimens.
Pursuant to this, they expect that they may identify potatoes with high levels of quercin - a flavonoid found in red onions.
The team also studied five different kinds of kukoamines in potatoes - compounds purported to help control blood pressure levels - although it remains to be established the level at which these would need to be present in order for one serving to provide sufficient useful quantities.
Until now, the only other identified source of kukoamines was Lycium chinense, a medicinal plant from China.
"Phytochemical profilers investigate potato benefits"