Electric shocks are used to heat gluten-free bread from the inside – successful baking while saving energy and time compared to conventional baking applying heat from the outside. This was among the findings of a recent study by the Institute of Food Technology of the University of Natural Resources and Life Sciences (BOKU) Vienna, published in an international journal.
A technology named Ohmic heating was used and adapted to the production of gluten-free bread. First results showed superior quality of the Ohmic bread while energy and time were saved during the manufacturing process.
The principle is well known from the good old light bulb - an electrical current passing through a wire heats it up until it glows. This is due to its electrical resistance and the Ohmic law leading to the dissipation of electrical energy into heat.
Taking a bread dough instead of a metal wire results in the same effect – it is not glowing but heating up. And the heat can be used to bake the product.
This was done by a team led by Henry Jäger from the Institute of Food Technology at BOKU Vienna. This smart solution was, in particular, used for gluten-free bread that is challenging to bake.
Hot flashes
“The heat is generated instantaneously in the complete dough,” said Jäger, adding, “This is the main advantage of the Ohmic heating technology. Conventional baking in the oven requires more time since the heat needs to penetrate from the outside towards the centre of the dough.”
This slow heating is a major limitation for the manufacturing of gluten-free bread. Wheat protein, the gluten, which is usually responsible for the dough structure and its expansion is missing in these products.
Starch is used as a replacer in order to take over this function. Sufficient heating causes the starch to gelatinise and to contribute to the crumb structure.
However, a much larger portion of water is needed in the dough which results in a lower viscosity and makes it thinner and more liquid. This is challenging for the subsequent baking.
Jäger’s team realised that the rapid and uniform heating of the whole dough is one of the major advantages obtained from Ohmic heating with a benefit for the production of gluten-free bread.
“In order to really benefit from these advantages and obtain best results, the optimal process and product characteristics had to be identified,” stated Jäger, adding, “Achieving such convincing results and improving the efficiency of the process at the same time was finally also surprising for us.”
Quality
The Ohmic bread showed excellent quality characteristics compared to conventionally baked products. The volume of the bread was 10-30 percent higher. The crumb was softer and more elastic and the pores were smaller and more evenly distributed.
But the team did not just rely on the physical quality characteristics of the bread and looked into the nutritional aspects and its digestibility as well.
“Taking into consideration the short baking time during Ohmic heating, a negative impact on starch digestibility might occur,” stated Regine Schönlechner, senior author of the study. However, tests performed by in-vitro-methods did not reveal any differences.
The superior quality of the gluten-free Ohmic bread was accompanied by savings of energy and time.
The first trials indicate savings of around two third compared to the energy needed for conventional baking. Also, the Ohmic baking needs much less time compared to the conventional process.
In just a few minutes, the dough is converted into a ready-to-eat gluten free bread. Browning and crust formation do not occur, so that the bread can be used directly for applications such as toast or tramezzini bread. If a crust is desired, it can be formed afterwards in a controlled manner by infra-red heating.
Recipe for success
Special equipment from the BOKU Core Facility Food and Bio Processing was used by the team for the development and optimisation of this promising baking concept.
The core facility provides expertise and high-tech equipment for research and development to academia and industry.
In this study, it was used to identify the exact conditions that result in major benefits from the Ohmic heating to the baking of gluten-free bread. This was achieved by performing various trials applying different combinations of electrical power input and duration of different baking steps.
“At the end, the subsequent application of three different process intensities with different holding times showed to be the most suitable option,” said Jäger.
He added, “An initial baking step at 2-6 kW for 15 seconds followed by 1 kW for 10 seconds and a final baking at 0.3 kW for five minutes is the recipe for the successful production of gluten free-bread using Ohmic heating.”
