Evaluation of the effect of cheese powder and ultrasonic wave on physicochemical and sensory properties of gluten-free oil cake

Celiac disease leads to the malabsorption of nutrients and damage to intestinal mucosa. High nutritional value is one of the advantages of dairy powders, associated with their high calcium, protein and essential amino acid contents. Research has shown that such powders boost the gluten quasi-network by forming interfacial films. They are also able to increase the moisture, improve the organoleptic properties, and retard the staling of gluten-free bakery products. In addition, it has been reported that ultrasonic waves can accelerate the oxidation and increase the aeration, volume, porosity and moisture content of bakery products. They can also reduce the hardness and improve the color of such products, thus resulting in the enhancement of their quality and marketability. Consequently, the aim of this study was to improve the appearance, flavor and texture of the gluten-free cake based on rice, germinated quinoa and potato flour using cheese powder at 0, 3, 6 and 9% and ultrasound intensity of 0, 30 and 70% for 5 min.

In this study, cheese powder at 0, 3, 6 and 9% and ultrasound intensity of 0, 30 and 70% for 5 min were used to improve the quality of gluten-free cupcake. Control cake formulation had 70 g rice flour, 15 g germinated quinoa flour, 15 g potato flour, 52 g sugar, 50 g water, 36 g egg, 36 g oil, 12 g invert syrup, 2 g baking powder, 0.2 g vanilla, 1.5 g guar gum and 0.5 g xanthan gum. Moisture, specific volume, firmness, crust and crumb color, sensory properties, porosity and scanning electron microscopy (SEM) (with 100× magnification) were evaluated. To study the effect of processing parameters on color components of gluten-free cupcake, the RGB color space images were converted to L*a*b space. For determination of gluten-free cupcake porosity using image analysis, the color images were first gray scaled and then thresholded using isodata algorithm. The porosity was measured from the ratio of white to the total numbers of pixels. Results were reported as the average of three replications. In order to assess significant differences among samples, a complete randomized design of triplicate analyses of samples was performed using the Mini-Tab17. Turkey’s new multiple range tests were used to study the statistical differences of the means with 95% confidence.

Results revealed that moisture content increased as the cheese powder and ultrasound intensity were elevated. Cheese powder caused the moisture content to increase by boosting the gluten quasi-network and ultrasonic waves brought about this phenomenon by dissociating the polymeric chains of starch molecules and forming hydrogen bonds between water molecules and free hydroxyl groups. The sample containing 6% cheese powder sonicated at 30% intensity had higher specific volume (4/4 Cm3/g) and porosity (31.2%) as well as lower hardness (3.4 and 4.4 N after 2 hours and one week respectively) compared with other samples. Cheese powder, by boosting the gluten quasi-network and improving the dough elastic properties, and ultrasound, through enlarging the air bubbles present in the dough, caused an increase in the porosity, specific volume and softness. The results also indicated that the rise in the cheese powder content up to 6% led to an increase in the L* value (from 44.9 to 53.5) and up to 9% in the a* value (from 2.6 to 8.4) of the gluten-free cupcake crust. On the other hand, the results demonstrated that as the ultrasonic intensity was increased, the L* value of the gluten-free cupcake crumb also increased (from 60.3 to 77.9), while its b* value was reduced (from 17.3 to 7.9). This could be due to the aeration and oxidation acceleration which resulted in the increased whiteness and decreased yellowness of the cake crumb. Finally, the findings of sensory evaluation showed the preference of the samples containing 3 and 6% cheese powder sonicated at 30% intensity (4.2 and 4.4 score). The SEM and binary images of the preferred samples also confirmed the integrity of the internal structure and the gluten quasi-network of these samples, compared with the control.