Measuring Texture of Dough - extension, inflation and stress relaxation

Bread is one of the oldest foods, and holds an immense historical value. The word itself has such cultural gravitas that it is often used as a metaphor for basic, general necessities.

With snack and bread products currently dominating the top five grocery brands in the UK, and the bakery market set to grow by 12.6 per cent by 2011, bread clearly still holds its centuries-old position as a dominant, staple food source.

Just as mankind has evolved, so has bread. Today, the market for bread is diverse and highly competitive. Thousands of intrinsic and superficial product variations present consumers with an abundance of alternatives. One thing remains constant however – the fresher the bread, the more appetising it is to the consumer. Texture is a key factor in perception of freshness.

The analysis of dough characteristics can be enough to predict end product texture and freshness perception. It is therefore essential that manufacturers invest in thorough physical characterisation during the earlier stages of production, to ensure efficiency and, most importantly, customer satisfaction.

The formulation of a dough is the unanimous prime determinant of its physical and behavioural traits as a finished bakery product. Many of the textural properties of bakery products depend on the earliest steps of the dough making process – notably the interactions between the main ingredients (flour, water, yeast) and air.

By the time the dough has been mixed, its rheological characteristics are already determined. It is therefore essential that the optimum formulation of ingredients be achieved at the earliest stages of the manufacturing process. The use of texture analysis at this point can help guarantee the ideal dough texture and so minimise the risk of unnecessary financial and material losses for the manufacturer, retailer or consumer. In a market where competition is fierce and brand loyalty high, there is no room for inferior quality.

What’s the testing solution?
An innovation from Stable Micro Systems is the Dobraszczyk/Roberts Dough Inflation System, which is both time and cost-efficient. This analytical instrument, easily fitted to the TA.XTplus texture analyser, recreates conditions similar to the strain experienced around a slowly expanding gas cell and, uniquely, has the ability to test smaller sample sizes. This will be of interest to research and wheat breeders where only small flour samples can be obtained.

A sheet of dough is inflated by volume displacement of air, inside a customised temperature chamber, which can inflate it in temperatures of up to 60ºC. This chamber houses samples during their pre-test equilibration period, as well as providing a controlled temperature environment for more realistic assessment. 

The pressure and volume of the dough bubble are measured during inflation, and can subsequently be used to calculate such parameters as the strain hardening index of the dough. This offers a precursory warning as to any potential deformation in the dough, allowing manufacturers to predict product anomalies and consequently eliminate them.

Rolling in the dough
As pieces of dough are separated and rounded, the balance of their viscoelastic components is critical. A dough that is too elastic is awkward to manipulate and so will often result in a misshapen end product, which will be rejected by the manufacturer. Likewise, a dough that is too viscous will not hold the desirable end structure.

Inflation and stress relaxation are important indicators of dough extensibility. Resistance to extension and extensibility are important indicators of bread dough quality. Assessment of these characteristics can give a good suggestion as to how well a dough will react to the baking process. By expanding the dough through volume displacement of air, pressure during inflation, as well as the volume of the dough bubble at burst point, are measured. This allows certain textural properties to be quantified.

Traditional physical characterisation methods – such as the AACC standard – require large quantities of dough and are time consuming, making them impractical for manufacturers.

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This testing solution is just one example of methods and equipment available for the testing of bakery products. To view more examples, visit our page detailing Bakery Applications.