Researchers discover the power of fibre in chickpeas

Fibre consists of tough plant-derived materials that the body’s digestive system cannot easily break down. When fibre reaches the large bowel (colon) it provides a beneficial food source for the trillions of bacteria in the gut. Eating enough fibre is important to keep your bowels healthy and can also help you feel full, which means you're less likely to eat too much.

However, most adults in the UK do not eat enough dietary fibre to meet their daily target intake. One of the challenges is that many processed foods are made from refined grain, which contains less fibre than whole grain. The source and type of fibre is also important, and the fibre structures found in processed or refined grains do not necessarily have the same beneficial effects as those found in whole grain.

So, researchers at the Quadram Institute at Norwich Research Park, in collaboration with a team at King’s College London, have been studying fibre and looking for new ways to preserve the most beneficial forms of fibre into everyday processed foods.

Their recent study, published in the leading scientific journal Nature Food, showed how different food processing treatments affected dietary fibre structures of wheat and chickpeas. Whole grains were shown to contain fibre as structurally complete plant cell walls that surround the cell, but when wheat and chickpea were milled into flour, the cell walls and the dietary fibre were broken up into smaller pieces.

Researchers at the Quadram Institute have been studying how food processing treatments affect dietary fibre structures of wheat and chickpeas (pictured) (Image: Quadram Institute)

The researchers then used models of the human digestive system to observe how dietary fibre structure affected the digestion of carbohydrates. When wheat and chickpeas were processed by milling, the disrupted fibre structure caused the carbohydrates within to be digested far more quickly than when that structure was intact.

Chickpeas also emerged as a better source of dietary fibre than wheat. When chickpeas were cooked whole, the cell walls were not only thicker than in wheat, but also tougher and not as easily damaged by cooking. Using models to study their digestion revealed that the fibre structure in whole, but not milled, chickpeas acts as a protective barrier that greatly slows the digestion of carbohydrate.

What this research shows is how common food processing treatments like milling and cooking can profoundly change fibre structure, affecting how we digest carbohydrate, which has implications for blood sugar levels.

The study also raises many questions about the efficacy of fibre supplements because some of fibre’s benefits may be lost if the walls of the plant cells are damaged.

This image of PulseON® enriched bread, shows the intact plant cells from PulseON® flour (blue) mixed with gluten (orange) and wheat starch (green) in the structure of bread (Image: Quadram Institute)

Eating whole cooked chickpeas and other pulses is a great way to boost fibre intakes, but diet survey data shows that these are only a minor component of typical UK diets. The new knowledge of food processing techniques led the scientists to create a new ingredient called PulseON®, made using different milling and drying techniques to retain the natural cellular structure and slow-release carbohydrate.

The results of a recently-published human trial found that partly replacing wheat flour with PulseON® in foods like white bread lowered blood glucose response by 40pc, without affecting the taste.

The researchers hope that the food industry will be able to use PulseON® instead of refined flour in processed foods to make it easier for consumers to reap the nutritional benefits of pulses.

Dr Cathrina Edwards is lead author of the study at the Quadram Institute into how different food processing techniques can have a profound effect on how the body handles fibre in our diets (Image: Quadram Institute)

Dr Cathrina Edwards, lead author of the study at the Quadram Institute, said: “We have shown how a better understanding of fibre structure can help to design fibre-rich food ingredients and products that are likely to be much more effective in helping manage blood glucose and so maintain and reduce risk of type 2 diabetes.”

FIBRE FACTS

• Dietary fibre is found in the cell walls of plants and helps to maintain a healthy gut.
• Some types of dietary fibre can slow the release of carbohydrate from food.

• Whole pulses (chickpeas, beans and lentils) are great sources of fibre and slow-release carbohydrate.

• Eating enough fibre can help prevent type 2 diabetes, heart disease and stroke.