Have your (low GI) cake and eat it

Posted on February 23, 2015

Food with a low glycaemic index (GI) is generally considered healthier because it is digested at a slower rate than high GI food, thus providing sustained energy release. However, many people prefer high GI food such as cake because it simply tastes better.

Research by Prof Mohammad Naushad Emmambux, associate professor at UP’s Department of Food Science, and his colleagues has shown that it is possible to modify high GI starch using fatty acids so that it becomes a low GI starch. This means it should soon be possible to make low GI foods that taste as good as high GI foods.

‘Starch can be modified in various ways using chemicals, but nowadays consumers prefer “clean labelling”, meaning they don’t want to use starches that have been modified using synthetic chemicals,’ says Emmambux.

 The glycaemic index (GI) of a particular food indicates that food’s effect on a person’s blood glucose (also called blood sugar) level. Glucose is one of the body's main sources of energy. Low GI foods are foods with a low glycaemic index, which have a slower rate of digestion and absorption than higher GI foods.              

‘What we demonstrated in the lab is that you can use fatty acids, which are food-friendly chemicals that qualify for clean labelling, to modify various starches that have potential to lower their GI.’

Starch contains two molecules, namely amylose and amylopectin. Emmambux’s team showed that when certain starches are cooked in water with fatty acids, the amylose reacts with the fatty acids to produce amylose-lipid complexes. The presence of these complexes changes the functionality of the starch.

‘This can potentially result in four applications, the first of which is that the starch becomes more slowly digestible by enzymes – making it low GI. Secondly, it makes the starch non-gelling, which means it becomes more stable when freezing. If you were to put porridge made of the modified starch into the fridge, it wouldn’t become hard like normal porridge, but would stay much softer.

‘Thirdly, the modified starch can be used as a fat [replacement], for instance in mayonnaise. And finally, we also found that the amylose-lipid complexes, which are digestible and biodegradable, form at the nano scale, creating an edible food-based nanomaterial. We believe this could, for instance, in future improve the properties of bioplastic films used in food packaging.’

Emmambux demonstrated this process in the lab using three different types of cereal starch (maize, wheat and tef). His team has not done any in vivo studies, so the process is yet to be tested in animals and people. However, he is confident that the technology has a lot of potential.

‘It should be possible to make low GI cake using this process, and the other applications are also very promising. We are already working with the local starch industry to look at various options for commercialisation.’

Emmambux is also working on finding food-friendly ways to modify amylopectin molecules in starch to make it similarly less digestible as well as to improve the stability and release of vitamins by protecting them from the harsh environment of the stomach through encapsulation.


- Author DUR

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