Could white bread be healthier with new chickpea flour?

A new ingredient to replace refined carbohydrates in staple foods has been developed, according to new research.

The study by the Quadram Institute and King’s College London found the blood glucose response to white bread was lowered by 40% in a human trial.

The researchers showed that replacing wheat flour with a new ingredient derived from chickpeas improved the glycaemic response of people eating white bread.

The ingredient uses specially developed milling and drying processes that preserve cellular structure, making its starch more resistant to digestion. Developing food products that contain more of this resistant starch could help to control blood glucose levels and reduce risk of type 2 diabetes.

Starch from wheat is a major source of dietary carbohydrate, but in bread and many other processed foods it is quickly digested to glucose in the body, causing a large spike in blood glucose levels. There is a large body of evidence that links long-term consumption of foods that provoke high glycaemic responses to the development of type 2 diabetes. With this condition on the rise, along with obesity and other metabolic disorders, providing foods and ingredients that help consumers better manage blood glucose could help combat these challenges to health.

Many pulses, such as chickpeas, peas, beans and lentils, naturally contain high amounts of resistant starch, which is digested slowly and avoids potentially damaging blood glucose spikes. But most of this beneficial resistance is lost, rendering the starch highly digestible, when these crops are milled to flour and processed into a food product.

For this reason, the scientists invented an alternative milling process, which preserves the plant cell wall structures (dietary fibre) that surround the starch. This ‘Type 1’ resistant starch is the same as that found in wholefoods, but this new ingredient can be used in a form that potentially allows it to be incorporated into a wider range of foods.

Funding from the Biotechnology and Biological Sciences Research Council (BBSRC) was used to develop the commercial potential of this novel ingredient, referred to as PulseON, and expands the possibilities for including large amounts of resistant starch in processed foods to improve nutritional quality.

Left picture: PulseON flour, looked at under the microscope, shows the starch (green) remains inside the plant cell wall (blue), which protects it from digestion. Right picture: In normal milling and processing, many plant cells rupture, exposing the starch (green) and making it much more digestible. Image credit: Quadrant Institute.

The research team showed that the resistant property of the starch is retained during breadmaking, and that people who ate bread rolls where some wheat flour was replaced by PulseON had lower blood glucose responses.

In a double-blind randomised crossover study, the scientists replaced 0%, 30% or 60% of the wheat flour in a standard white wheat bread recipe with PulseON.

Healthy human participants consumed each type of bread roll type for breakfast in random order on separate days, with no knowledge of which type of roll they were eating. Their glucose levels were recorded using continuous glucose monitors.

Blood glucose responses to the PulseON enriched breads were on average 40% lower than after eating the control breads. All bread rolls contained similar amounts of starch and wheat protein (gluten) per serving, so the different blood glucose responses reflect the carbohydrate quality, the report said.

These results raise the possibility of using such foods for improving the dietary management of diabetes, which needs to be evaluated in future studies.

The digestion of starch in each bread type was also studied in a laboratory using biochemical and microscopy techniques. These experiments showed that after two hours of digestion, the wheat starch had been digested, but the Type 1 resistant starch remained.

This confirms that the lower glucose response to PulseON enriched breads was due to the resistant starch enclosed in the chickpea ingredient not being digested.

Dr Cathrina Edwards from the Quadram Institute said incorporating the new type of flour into bread and other staple foods provides an opportunity to develop the next generation of low glycaemic food products to support public health measures to improve health through better diets.

“Consumers replacing wheat bread with PulseON enriched bread would benefit not only from the type 1 resistant starch, but also from the higher fibre and protein content,” she said.

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