Turkish food engineers, writing in the International Journal of Food Science and Technology, reported that the addition of chestnut flour up to a certain concentration improved the quality of gluten-free breads significantly.
They also comment that breads baked in infrared–microwave combination oven at the optimum conditions had statistically similar quality with conventionally baked ones in terms of colour, specific volume and firmness, while baking time of was cut by 64 per cent.
The authors note no previous study looking at the optimisation of formulations and processing conditions for gluten-free breads to be baked this way.
Microwave over conventional ovens
The use of microwave over conventional ovens can bring energy efficiency, space saving, and food with high nutritional quality but the authors stress that there are associated quality problems including high moisture loss, firm structure, rapid staling and lack of surface browning, flavour and crust formation.
“To overcome these problems, the combination of microwave with infrared heating has been recently used by several researchers,” remarked the researchers.
Chestnut flour provides not only health and nutritional benefits but also some functional properties to the dough including stabilising, texturising and thickening attributes, continued the authors.
But they caution that a high amount may worsen product quality, giving low specific volume, firm texture, dark colour and bitter taste. “Thus, the drawbacks associated with using only chestnut or rice flour may be overcome by the synergistic effect of using of chestnut and rice flour together in the formulation,” they said.
The study
Rice flour mixed with different proportions of chestnut flour and different emulsifier contents were used to prepare breads, said the team.
To improve heating uniformity of samples, a rotary table was introduced into the microwave-infrared combination oven, they continued.
Two halogen lamps (1500w) were located at the top of the oven and one (1500w) was at the bottom. To maintain the humidity in the oven, beakers containing 400 ml of water were placed in the corners of the oven during baking. Four dough samples of 100 g each were placed at the centre of the turn table for baking, said the team.
Gluten-free breads and wheat breads baked in conventional oven were used for comparison, they reported, with weight loss, firmness, specific volume and colour change of the breads evaluated.
Response surface methodology (RSM), explained the authors, was used to optimise gluten-free bread formulations and processing conditions.
RSM is an effective way, argue the authors, to examine the relationship “between the responses and factors. It is used to minimise the number of trials and to provide multiple regression approach for optimisation of ingredient levels, formulations and processes in food technology.”
Comparable quality
Using this method, the food engineers found that breads containing 46.5 per cent chestnut flour with 0.62 per cent emulsifier and baked using 40 per cent infrared and 30 per cent microwave power for 9 minutes had “statistically comparable quality with conventionally baked ones.”
Moreover, “conventional baking time of gluten-free breads was significantly reduced,” added the engineers.
Source: International Journal of Food Science and Technology
Published online ahead of print: doi:10.1111/j.1365-2621.2011.02682.x
Title: Optimisation of formulations and infrared–microwave combination baking conditions of chestnut–rice breads
Authors: I. Demirkesen, G. Sumnu, S. Sahin, N. Uysal