A research team led by Professor ZHOU Weibiao from the Department of Food Science and Technology at the NUS Faculty of Science has shown that compounds extracted from red dragon fruit peel can be incorporated into bread to increase antioxidant activity and slow starch digestion, offering a potential pathway to healthier staple foods and reduced food waste.

Enhancing the nutritional value of everyday staples

The study integrates a purified betacyanin-rich extract (PBRE) derived from red dragon fruit peel into wheat bread at controlled concentrations. At an optimal fortification level of 0.75 per cent, the extract improves dough structure and bread texture while delivering measurable nutritional benefits.

Moving beyond the anthocyanin extracts they had previously studied, the NUS team turned to betacyanins from red dragon fruit peel—a novel and promising alternative for bread fortification. While the extraction methods are similar, betacyanins are more stable at common food pH levels and dissolve easily in water. This allows lower doses and more reliable interactions with gluten during processing. Additionally, in vitro studies indicate that betacyanins have higher bioavailability than anthocyanins, suggesting they may be more readily absorbed and could potentially deliver greater nutritional benefits.

“Functional staples such as PBRE-fortified bread provide a practical way to incorporate bioactive compounds into daily diets. With diabetes rates increasing globally, improving the nutritional quality of commonly consumed foods may help reduce glycaemic load and enhance antioxidant intake without requiring major changes in eating habits,” said Prof Zhou, who heads the NUS Department of Food Science and Technology.

Laboratory tests showed that betacyanins interact with gluten proteins in the dough; at moderate levels, the dough rises better, while high concentrations reduce dough elasticity and lead to compromise bread quality. To strike the right balance, NUS researchers identified 0.75 per cent fortification as the most effective level for maintaining baking quality while achieving nutritional gains.

The fortified bread demonstrated substantially higher antioxidant levels than conventional bread and slower starch breakdown during digestion, resulting in a lower estimated glycaemic index. The findings were published in the scientific journal Food Chemistry on 25 December 2025.

Turning food waste into functional ingredients

At a time when global food waste is at historically high levels, the NUS team see added value in converting agricultural by-products that are typically discarded into functional food ingredients. Instead of using whole fruit peel, the team worked with a purified extract to achieve more accurate and consistent results, while demonstrating how food waste can be reused in food production.

The researchers are now studying how similar natural extracts can be added to other everyday foods, to help reuse food waste and improve both food nutrition and production efficiency.