All clear for tiny capsules of goodness
22 December 2011
Vitamin D and epigallocatechin gallate (an antioxidant found in green tea) were loaded into nanocapsules to be added to drinks to deliver health benefits
Yoav Livney and his team from the Technion, Israel Institute of Technology, in Haifa, used the Maillard reaction to create protein-saccharide conjugate nanocapsules. This natural reaction, which causes the typical browning of food during baking and cooking, has been used to make similar conjugates to encapsulate hydrophobic nutrients, but the resulting capsules were large and turned liquids cloudy.
To overcome this problem, Livney's team conjugated oligosaccharides derived from starch to the milk protein casein. The conjugate molecules underwent spontaneous self-assembly into a core-shell nano-structure with a bulky hydrophilic layer, leading to a large degree of curvature and so to nano-sized capsules. The capsules were so small that the drinks they were added into remained clear.
The team trapped vitamin D (a deficiency of which can lead to rickets and other disorders) and epigallocatechin gallate (found in green tea and linked to the prevention of many diseases, including cancer) inside the capsules and monitored their release during digestion. They found that the nanocapsules kept the nutrients trapped during gastric digestion. Livney predicts that enzymes excreted in the small intestine will easily break down the saccharide-protein core-shell structure, making the micronutrient cargo bioavailable for absorption.
The team also found that the capsules didn't just deliver vitamins, they also protected them. 'They conferred significant protection against vitamin D degradation at low pH, and during product refrigerated shelf life,' says Livney.
It's the building blocks of this system that are essential for its future use, says Cristina Sabliov, an expert in nanoencapsulation of bioactive components from Louisiana State University, US. 'This type of research, focused on food-grade components for delivery of bioactives with important health benefits, is critical for the development of safe, taste pleasing, stable and nutritious foods,' she adds.
In the future, Livney plans to 'evaluate the entire release profile of the nutraceutical during simulated digestion, and later, to test its bioavailability in vivo, preferably in a clinical trial.' He adds that 'encapsulating other bioactives by this method may also be studied'.
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G Markman and Y D Livney, Food Funct., 2012, DOI: 10.1039/c1fo10220f
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