The Turkish researchers, who published their findings in the journal Food Hydrocolloids, found that xanthan and xanthan–guar gum blend containing cakes were shown to have higher volume index, specific volume and porosity values.
They added that the baking method also had an effect on the quality of the rice cakes with those produced in infrared–microwave (IR–MW) combination ovens showing greater porosity over cakes baked by conventional means.
Rice containing no gluten, low levels of sodium, protein, fat and fibre, and a high amount of easily digested carbohydrates is desirable for certain special diets such as gluten-free food products. However, due to its low gas retention capacity, rice products have some quality problems such as low volume, poor texture, colour and crumb structure, said the researchers.
Gums act as polymeric substances mimicking the viscoelastic properties of gluten in bread dough, they note. However, said the authors, previous research evaluating gum in this regard has focused on the formulation of gluten-free breads, while studies on other gluten-free bakery products such as cakes, biscuits and pasta are limited.
Therefore, they explained that the main objective of their study was to obtain quantitative and qualitative information on macro and micro-structure of gluten-free rice cakes containing different types of gums and baked in different ovens.
A cake batter recipe containing 100 per cent rice flour, 100 per cent sugar, 25 per cent shortening, nine per cent egg white powder, three per cent salt and five per cent baking powder (all percentages are given on a flour weight basis) was used in the experiments, said the researchers.
The amount of water added to the batter was 27 per cent of the overall formulation, they added.
The authors said that gums including xanthan gum, guar gum, xanthan–guar gum, locust bean gum and k-carrageenan were added in the formulation as one per cent, which was determined by preliminary experiments.
Xanthan–guar gum was prepared by mixing these gums in equal proportions, (0.5 per cent each), while a cake batter containing no gum was used as control.
Rice cakes formulated with different gums baked in different ovens were cut into two halves vertically by a razor blade. The cut side of one of the halves was placed over the glass of a scanner, and scanning was performed with a resolution of 300 dpi.
The authors said that the micro-structure of gluten-free rice cakes was also evaluated with cake samples being frozen in liquid nitrogen and freeze dried before scanning electron microscopy (SEM) analysis.
The researchers found that the highest pore area fraction was obtained in cakes containing xanthan and xanthan–guar blend, while cakes baked in IR–MW combination oven had higher porosity than those baked in conventional oven.
Furthermore, they found that conventionally baked cakes showed more starch granule deformations.
Possibilities for a growing market
The gluten-free food market is blossoming and was worth almost $1.6bn last year, according to Packaged Facts. The market is experiencing a compound annual growth rate of 28 per cent over four years.
Sufferers of celiac disease have to avoid all gluten in their diet, but diagnosis is not the only factor.
Other sectors of the population, such as those who have self-diagnosed wheat or gluten intolerance or who believe gluten-free to be a healthier way of eating, are also strong drivers.
Volume 24, Issue 8, November-December 2010, Pages 755-762
'Quantitative analysis of macro and micro-structure of gluten-free rice cakes containing different types of gums baked in different ovens'
Authors: E. Turabia, G. Sumnu, S. Sahina