A research team from the National University of Singapore recently published a study stating that they successfully transformed the originally discarded red-fleshed dragon fruit peel into a functional ingredient that can be used in bread production. While significantly improving the antioxidant level of bread and slowing down the digestion rate of starch, it also provides new ideas for the food industry to utilize agricultural by-products.
The research was led by the team of Professor Zhou Weibiao from the Department of Food Science and Technology of the National University of Singapore. The researchers extracted a purified extract rich in betacyanins from the peel of red-fleshed pitaya and added it to wheat bread dough in proportion. Experimental results show that when the addition amount is 0.75% of the dough mass, the texture and taste of the bread are improved, and it also shows obvious nutritional advantages.
According to the research team, this work is based on previous research on anthocyanin-fortified bread, but the betacyanidin selected this time has better stability within the pH range of daily foods and is more easily soluble in water. Therefore, the dosage can be lower, and the interaction with the gluten network is also more stable. In vitro study results also suggest that the bioavailability of betacyanidins may be higher than that of ordinary anthocyanins, which means that it is more easily absorbed by the body and is expected to bring greater potential health benefits.
Laboratory tests further show that betacyanidin interacts with gluten protein in dough: when added in a moderate amount, it helps the dough ferment and expand, but if the amount is too high, it will weaken the elasticity and affect the baking quality. After comprehensively considering the baking performance and nutritional improvement, the researchers determined the 0.75% addition level as the "best balance point" that takes into account both taste and health effects.
Compared to regular wheat bread, bread fortified with pitaya peel extract had significantly higher antioxidant levels and showed a slower rate of starch digestion, corresponding to a lower estimated glycemic index. Zhou Weibiao pointed out that in the context of the rising incidence of diabetes worldwide, by optimizing the formula of frequently consumed staple foods, it is expected to reduce the overall dietary glycemic load and increase the intake of antioxidant ingredients without changing the public's eating habits.
In addition to nutritional improvements, this work also responds to the issue of food waste. The researchers chose to use purified peel extract rather than whole peels, on the one hand to control the content of active ingredients and obtain more reproducible experimental results, and on the other hand to demonstrate a realistic path for upgrading agricultural product processing by-products into high value-added food ingredients.
The team said that the next step will be to explore the application scenarios of similar natural extracts in other daily foods, with a view to improving the nutritional quality of food while promoting more efficient use of resources and reducing waste in the supply chain. Relevant results have been published in the magazine "Food Chemistry". The paper evaluates in detail the comprehensive impact of this type of extract on dough performance, baking quality and nutritional attributes.