Reducing sugar with extruded flour

Campden BRI's senior bakery scientist explains how a pre-processing technique can cut sugar in cakes by 20% without affecting functionality – a fact that could also make it useful in wraps, bread, soups and even sauces.

10 December 2019
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Meet the Expert

Who: Anne Vissers

What: Senior bakery scientist

Where: Campden BRI


When did you last consume some sugar? Chances are it was probably today. It’s a difficult ingredient to avoid, and yet it’s associated with so many negative health issues, from obesity to tooth decay.

As a result, consumers are beginning to avoid sugar or seek low-sugar ingredients, with food manufacturers responding by reformulating and developing products with less of the sweet stuff. This is being further encouraged by voluntary targets set by Public Health England in 2017 that urge a 20% reduction of the sugar in products – including biscuits, cakes, sweet confectioneries and breakfast cereals – by 2020.

Easier said than done!

Besides sweetness, sugar contributes to many of the quality characteristics of baked products: the caramelisation that produces the desirable golden-brown colour, structure formation and the soft textures created by sugar’s ability to bind water.

Therefore, if you reduce the sugar, an alternative ingredient is often needed to mimic one of these characteristics. You could potentially add many ingredients, but where do you draw the line? Let’s face it, consumers do not want to see an ingredients list longer than the packaging itself.

So, what’s the solution?

Working all flours

Extrusion is a pre-processing technique that can be used to optimise the nutritional value and techno-functionality of an ingredient. How does it work? Put simply, the extrusion process involves feeding a product through a rotating screw that subjects it to high shear. This increases pressure and temperature which, for wheat flour, leads to starch breakdown and protein denaturation; for consumers, it makes the flour easier to digest.

There’s also something for the bakers: the extruded flour’s starch gelatinises, which makes it adopt the water-binding properties that we usually rely on sugar to provide.

So, can you reformulate a product with extruded flour to ensure it behaves the same even when its sugar is reduced? In theory, yes, but what about in practice?

As part of our research into pre-processing for improved nutrition, we replaced 10% of a cake’s plain flour with extruded flour and reduced the sugar content by 20%. The result? According to a panel of sensory assessors, the cake maintained its appearance and firmness but, as you’d expect, it didn’t taste as sweet as the control cake.

However, the panel did comment that the reformulated cake was “still acceptable” as it had “a very nice crumb, appealing creamy colour and a good flavour.” After undergoing the extrusion process, we found the flour to produce caramelised notes that contributed to the cake’s flavour and masked the lower sweetness.

A palatable cake which looks almost identical to the control and achieves PHE’s 20% sugar reduction target sounds like a good starting point for producing clean-label products, but what are the challenges?

In cake, sugar plays a key role in lengthening shelf-life by reducing water activity, which hinders the growth of microorganisms. Our bakery scientists found that their reformulated cake had a higher water activity than the control. This creates concern over a potentially shorter shelf-life, a factor that food manufacturers must consider when using extruded flour in their products.

Next, we will determine the impact of extruded flour in other bakery products such as wraps and bread. Flour is also used as a key ingredient in soups and in sauces as a bulking agent, or to achieve a specific viscosity, so we will be looking at how extruded flour behaves in these applications, too.

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