Have your (low GI) cake and eat it

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 the University of Pretoria’s Department of Consumer and Food Sciences, 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.

Researchers

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  Professor Mohammad Naushad Emmambux

  Professor Mohammad Naushad Emmambux completed his undergraduate studies at the University of Mauritius and his postgraduate studies at the University of Pretoria (UP). He has been with UP for 22 years, and has been doing research for 16 years.

  “UP is a globally recognised, research-intensive university that provides a platform for growth, independent thinking and for making a difference to society,” he says.

  Prof Emmambux’s research is centred on the following:

  • Chemistry, nutrition and technology of plant food biopolymers (starch, protein and non-starch polysaccharides) in food and non-food systems;
  • Green/energy-efficient technologies such as extrusion, microwave and infrared for quick cooking, instant and convenient nutrient-dense plant-based foods
  • Food structure (micro, meso, nano and molecular) and rheology interface in food systems and processing

  His research contributes to the betterment of the world because it falls within the area of food and nutrition security. It addresses several Sustainable Development Goals (sDGs) including SDG 2: Zero Hunger and SDG 3: Good Health and Well-being.

  Prof Emmambux leads the food biopolymer research group in the Department of Consumer and Food Sciences; co-leads the technological innovation programme at the Department of Science and Innovation (DSF)/National Research Foundation (NRF) Centre of Excellence in Food Security; and leads the EU-funded InnoFoodAfrica project at UP. The two latter projects are cross-faculty initiatives that involve UP’s Faculties of Humanities, Health Sciences and Engineering.

  Over the past 18 months, Prof Emmambux and his research team have been working on reducing the glycaemic index (GI) of maize meal.  

  “We have found that complexation of starch with lipids as well as heat-moisture treatment increased the resistant starch content in maize meal porridge,” he explains. “The latter had a lower GI and the resistant starch comprising of amylose lipid complexes showed good prebiotic effects as it promoted the growth of good microbes and produced beneficial free fatty acids. We have a patent for manufacturing starch microspheres that are stable under mechanical stress. The starch microsphere can be used to mimic fat globules in food systems. Thus, we can reduce food calories by replacing fat.”

  The team has also shown that household-level technologies such as a microwave can change the oral processing properties of food to accommodate babies from the age of six to 24 months when complementary foods are introduced. “This will help to increase the nutrient density of complementary foods,” Prof Emmambux says.

  A recent highlight for the professor was presenting the EU-sponsored project InnoFoodAfrica at the New European Bauhaus Festival in June 2022.

  The research team has started two new projects: making protein nanofibers, which will be used as human tissue scaffolding, and making use of green chemistry to modify proteins from indigenous African plants; these proteins can be used in gluten-free alternatives.

  Prof Emmambux says his research matters because he and his research team are pushing scientific boundaries in the field of food science and technology. “We are making a difference by solving African and global problems related to food and nutrition security.”

  While no specific person has inspired him in his research effort, he says, “all my teachers, lecturers and supervisors are my role models and they have inspired me to become a good scientist”.

  He hopes to mentor the next generation of scientists who will help to create a better world for the future. His advice to school learners or undergraduates who are interested in his field is this: “If you have a curious mind and want to make a difference in the world, join the field of food science.”

  In his spare time, he meditates, spends time in nature and travels.

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