Writing in the Journal of the Science of Food and Agriculture , researchers from Centro de Desarrollo de Productos Bioticos del IPN and Universidad Central de Venezuela report that tortillas made from blue corn had less starch and a lower glycaemic index (GI) than their white counter parts.
"In addition to its perceived softer texture, the lower GI of pigmented tortilla may be attractive for people with particular nutritional or metabolic requirements," wrote lead author Juan Pablo Hernandez-Uribe.
The glycaemic index measures how quickly certain foods release carbohydrates into the body, which then raise consumers' blood glucose levels.
High GI foods cause blood sugar levels to rise more rapidly.
The researchers prepared tortillas from blue and white maize varieties and compared them with respect to in vitro starch digestibility - available starch (AS), total (RS) and retrograde (RRS) resistant starch contents, amylolysis rate and predicted glycemic index (pGI).
The blue tortillas were found to have lower AS, RS and RRS content after two days of storage.
The stored blue tortillas also had higher RRS content than their white counterparts.
"Blue corn tortilla exhibited higher protein and lipid contents than white tortilla.
Such a characteristic is important since both components may interact with amylose and longer lineal chains of amylopectin, a phenomenon that attenuates retrogradation," wrote the researchers.
"The lower total starch content of blue tortilla may result in decreased interactions among starch chains and lead to a softer texture of pigmented tortilla," they added.
Therefore, the blue tortillas had a lower pGI than the tortillas made from white maize, and this did not change during storage.
Such observations could be of interest to those adhering to a low GI diet, or diabetics who would benefit from lower prostprandial glucose increases.
An estimated 19 million people are affected by diabetes in the EU 25, equal to four per cent of the total population.
This figure is projected to increase to 26 million by 2030.
In the US, there are over 20 million people with diabetes, equal to seven per cent of the population.
The total costs are thought to be as much as $132 billion, with $92 billion being direct costs from medication, according to 2002 American Diabetes Association figures.
The researchers note that the pigments in the maize responsible for the blue colour are due to anthocyanins, which may offer nutritional benefits in addition to low GI.
"Nowadays, anthocyanins are of great interest from the nutraceutical or functional nutrition viewpoint owing to their perceived potential health benefits; they are considered natural antioxidants in view of their ability to trap free radicals, which produce molecular and cell damage," they stated.
Source: Journal of the Science of Food and Agriculture Published on-line ahead of print, doi: 10.1002/jsfa.3008 " Chemical composition and in vitro starch digestibility of pigmented corn tortilla" Authors: Juan Pablo Hernandez-Uribe, E. Agama-Acevedo, J.J. Islas-Hernandez, J. Tovar and L.A. Bello-Perez