Gluten-free ingredients: Perfecting formulations

A delicate balance: perfecting work with gluten-free ingredients

As gluten-free bakery is decisively increasing its foothold into the mainstream market, growing by about 25% each year, research seeks to improve product taste, texture and nutritional profiles. In the absence of gluten, this has been a challenge. It takes exact science and technology to define and improve digestive wellness.

+It all starts with the dough. Monitoring and thorough testing for ingredient variations will enable close control of the dough processing and, ultimately, the product’s quality; this is especially important when dealing with different types of gluten-free flour with varying characteristics. The goal is to reach the ideal dough viscosity, which is unique to each, from corn-based dough to chickpea-based dough, for instance. Baking trials will help determine optimum values in each case. Also, a fundamental understanding of the ingredients and their individual physicochemical characteristics, such as solubility, gelling and emulsification properties, can help to predict their impact on viscosity – a key indicator of the dough and the quality of the final baked good.

From the start of the process, the dough’s kneading properties offer useful information that can support formulation development. As single ingredients are added or changed, their effect on the whole dough system can be measured, necessary steps when developing products made by gluten-free flour. The International Association for Cereal Science and Technology (ICC) recently held a joint webinar with guest experts Aylin Sahin, a postdoctoral researcher at University College Cork (Cereal and Beverage Science Research Group), and specialists from Brabender – Stefan Jansen (application engineer) and Jessica Wiertz (manager Applications). We spoke with the specialists to further delve into the science explaining and supporting high-quality gluten-free bakery. “The right water absorption is one of the main important criteria for a proper crumb and a good product. Measuring the flour or the whole gluten-free formulation during kneading provides a helpful indication of how a gluten-free raw material acts during production. Moreover, different types of mixers cause different energy input during kneading which has a great impact on the development of any network,” they elaborate.

Viscosity control ensures quality

Consistent, quality gluten-free products begin with the incoming raw materials. Water absorption is an indicator that should be monitored from the start, as specialists recommend, to ensure the quality of incoming flour is as expected. In the R&D stage, when dough formulations are developed, the ideal viscosity is trialed or a certain viscosity can be targeted. For example, the target consistency for a chickpea flour will be 44 BU (Brabender Units), while corn flour will have 150 BU – vvalues based on dough systems including 2% hydroxypropyl methyl cellulose (HPMC, gluten replacer). Not only do the different types of gluten-free flours differ quite a lot, but there is also notable variation between different types of corn flours, the experts say. They illustrate that the particle size distribution is one of the factors responsible for this, e.g., if finely ground corn flour or corn grits are used; the target application for the flour analyzed also gives an indication for the right level of water absorption.

The International Association for Cereal Science and Technology

Today ICC is one of the foremost international organizations in the field dedicated to international cooperation, the dissemination of knowledge, and the improvement in safety and quality of cereal-based foods. The Association has its headquarters in Vienna, Austria with members from all five continents represented.

Stability at arrival (S1) [s] Stability at departure (S2) [s]

Consistency [BU] 600

500

Torque [BU] 400

300

200

Method used Sample size: 300g flour Mixing speed: 63 rpm Chamber temperature: 30°C Monitor torque – consistency 100

0

Farinogram with its typical evaluation points 100 Drop-off: Distance from consistency line to the mean torque after 20 min after water addition

Stability (S2) [s]: Time between S1 and S2

200 300 400

Time [s] 500 600 700

Source: International Association for Cereal Science and Technology

While raw materials may have varying characteristics, they should be within acceptable ranges to obtain constant quality gluten-free products, as each set of qualities may be suitable for certain applications. There are weak glutens and strong glutens, and several qualities in between; weak gluten flour is good for wafer production, for example, while wheat bread loaves are a better match for strong gluten flour. The specialists underline that protein content should be paid attention to, as it is a rough indicator for the flour’s performance, but protein quality is getting more and more into the focus: “Nowadays, it’s getting more common to describe the flour quality by protein quality instead of protein content.”

To differentiate among gluten qualities, the Brabender GlutoPeak offers methods for pure gluten analysis and for glutencontaining flour analysis. Within minutes, a characteristic gluten aggregation curve is recorded, and the quality and end use of the gluten or flour can be assessed. To optimize the water addition level, Brabender’s Farinograph, a rheometer with a sigma-blade-mixer, is well-established within the milling and baking industry. For the gluten-free flours, a modification of the existing mixer is necessary, the specialists note: “A tool called FarinoAdd-S300 is attached to the mixer and keeps the gluten-free dough in the mixing area.” This tool can be used to develop products with lesser-known raw materials, including hemp flour, buckwheat and quinoa.

Ingredients and recipes

The most important functional ingredients of a gluten-free dough and bread are the hydrocolloids and proteins. Both play an important role in terms of water binding, and also improve the visco-elastic properties of the system. Furthermore, sourdough can be added to the formulation to improve the baked good’s quality, the specialists highlight. Lowering of the pH value this way has several benefits, from increasing shelf life to reducing staling and lowering the pH of the system.

When formulating gluten-free products with additional ingredient claims, dietary fibers are a popular choice. They mainly influence the water absorption; however, they also physically affect the dough network. It might be therefore necessary to take countermeasures, e.g. by a pre-treatment of the fiber, which can be done by milling, hydration or functionalization, Brabender’s experts recommend.

To further enhance the nutritional profiles of gluten-free goods, plant proteins are a good place to start. In this scenario, the maximum level of protein content in the range of an acceptable sensory profile has to be determined, first of all. To further improve sensory characteristics, the combination of different protein types as well as the addition of enzymes can help. The specialists also recommended assessing the maximum level that can be added as they can affect the product’s mouthfeel. To optimize sensory characteristics, pre-milling, pre-hydration or heat treatment can be used. The addition of hydrocolloids together with the fiber as a premix can be suitable; alternatively, enzymes can be used.

In conclusion, accurately monitoring the process and the ingredients supports the further developments for all characteristics of gluten-free products, from working with functional replacers to improving the product’s taste and shelf life. +++

Process design using forced dough relaxation

By means of invasive mechanical and electrical impulses, the dough resting time of wheat doughs after mechanical energy input can be drastically shortened and dough properties equivalent to those of rested doughs can be achieved quickly in seconds.

Figure 1: Schematic representation of the gluten structure immediately after mechanical stress (left), as well as its change through a rest period or forced relaxation (right)

+The mechanical/electrical stimulation for the optimization of the dough resting time for wheat pastries is an AiF/FEI funded research project, which was carried out at the TU Munich, Chair of Brewing and Beverage Technology in the working group Grain Technology and Process Engineering. The project aims to reduce the time-consuming and process interrupting rest periods in bakery production to a minimum, so that the process steps of dough relaxation can be integrated in-line into existing processes and process interruptions due to rest periods, can be eliminated. Although some engineering-based solutions are already available for continuous dough processing without relaxation phases (e.g. extrusion processes), these are often unsuitable due to the size of the plant. Alternatively, they often represent special solutions for specific applications [1] and, in some cases, result in products with modified textural properties [2]. Consequently, the solutions currently available on the market are unsuitable for most products and companies. As a result, more complex processes with the intermediate step of dough resting have to be observed for most baked goods.

This is due to the structural properties of wheat dough. After a mechanical energy input, such as kneading, the gluten network is very elastic. This limits the dough's ability to be processed by machine. In the subsequent resting phase, the gluten network is restructured, which changes the mechanical properties of the dough. Relaxed doughs are more plastic and have a higher extensibility and yielding. This change in the dough properties is an absolute prerequisite for successful further processing. Without them, perfect dough division or shaping by machine would be drastically impeded [3]. Depending on the kneading technique and gluten quality, these resting times range from 10 to 30 minutes [4]. Depending on the product, many companies also use rest periods between the rounding and long molding, as otherwise the surface could burst open due to the excessive stress during baking. The sequence of mechanical loads with subsequent relaxation phases is therefore essential in order to develop the desired structural properties in the end product. A method that enables dough properties corresponding to those of rested doughs to be achieved in just a few seconds therefore represents a significant potential for process optimization and shortening for all doughs containing gluten. Particularly in view of the fact that every German household on average consumes just under 58.9 kg of bread and baked goods per year and 67% of these baked goods come from bakeries of an industrial character [5], the integration of dough resting in the ongoing process (in-line solution) would be associated with a high potential for

Figure 2: Illustration of the methods of forced relaxation by means of a) alternating voltage pulses, as well as d) ultrasound and the resulting mechanical dough properties. Measurement of the extensibility by means of micro tensile test (Kieffer Rig method) for doughs of different lengths (b & e) and forced doughs by means of alternating stress (b) and ultrasound (e). Measurement of dough fexibility by compression test for doughs of different lengths (c & f) and forced doughs by alternating voltage (c) and ultrasound (f).

© TUM

increasing efficiency. However, regardless of the size of the company and the degree of automation, shortening the dough resting time basically allows for a simplification and shortening of the process sequences.

Invasive impulses, mainly electrical, but also partly mechanical, have proven to be suitable to accelerate the restructuring processes of the gluten network during the resting period. The electrical pulses are applied in the form of alternating voltage in a voltage range between 110 and 260 V for application times of 1-5 seconds. For the application of mechanical pulses, high-energy sound (20 KHz) with amplitudes of 5 to 30 µm and application times of 30 to 120 seconds are used. The experimental setups are shown in figure 2 a) for alternating voltage and 2 d) for ultrasound. Immediately after kneading, the doughs are subjected to forced relaxation and compared with the properties of unrested and rested wheat doughs via various laboratory analyses and baking tests. Forced relaxed (voltage treatment) doughs in particular show the same behavior as rested doughs in all measured properties (extensibility, yielding, relaxation behavior). Figure 2 b) shows that the elongation of a forced relaxed dough (200 V, 2 sec) corresponds approximately to that of dough that has been rested for 25 minutes. Looking at the softness, the potential of forced relaxation becomes even clearer: here, the softness of the forced relaxed dough corresponds to that of dough rested for 50 minutes. For the ultrasonically treated doughs, the effect on the extensibility is similar to the effect of a voltage treatment (Fig. 2 e)). Here, too, elongation is achieved that corresponds to dough that has been rested for 15 to 20 minutes. However, ultrasound shows no effect on the extensibility. In this case, the ultrasonically treated dough corresponds to the dough that has not been rested (Fig. 2 f)). These corresponding viscoelastic dough properties between forced relaxed dough, especially voltage treated dough, and conventionally rested dough show that the restructuring processes of the gluten network can be forced and controlled by electrical or mechanical impulses.

Since the impulses used for forced dough relaxation are invasive applications that actively modify biological structures, it is essential to assess the vitality of the yeast and the baking capability of the dough. Standard baking trials with tin loaves of white bread serve this purpose. Doughs that rest for 0, 10 or 20 minutes between kneading and processing are used as a reference. The forced relaxation is also carried out between kneading and processing by means of alternating voltage (260 V 1 sec) or ultrasound (amplitude 18.9 µm 60 seconds). The remaining process steps (kneading, proofing and baking) are kept identical in order to allow a comparison of the two processes. After baking, the breads are analyzed by measuring the volume, crumb hardness and pore pattern. As already indicated in the results of the dough analysis, the identical properties of the forced relaxed and conventional rested breads can be confirmed with regard to their volume and crumb hardness, especially for voltage treated doughs