The effect of ultrasonically prepared resistant starch on structural characteristics and physicochemical properties of batter and cake

In this context, changes in starch digestibility and physicochemical properties under a combination of ultrasound-assisted acid hydrolysis (UAH)/commercial acid hydrolysis (AH) and heat-moisture treatment (HMT) were investigated. UAH was done by using 3M HCl at 40 ̊C in an ultrasonic bath with an output power of 350 W for 45 minutes. AH was done under the same condition while no ultrasonic device was applied. HMT was done at 25% moisture content at 110 ̊C for 2 hours. Subsequently, the starch with the highest amount of RS (UAH-HMT) was included in the sponge cake formulation at five levels of 0 (control), 10, 20, 30 and 40%. The results showed that HMT-UAH samples represented the highest amount of RS (19.41%) compared to native corn; NC (4.56%), HMTNC (11.24%) and HMT-AH (13.72%). Heat-moisture treatment increased the parameters such as gelatinization temperatures (To, Tp, Tc, and ΔT) and oil absorption capacity (OAC) of the samples, while other parameters including swelling power, solubility, and enthalpy of gelatinization were decreased. The micrographs of the scanning electron microscope (SEM) of the starch’s granules revealed some cracks and holes on acid hydrolyzed starch, while HMT did not alter the morphology of the granules. The increasing level of HMT-UAH RS significantly reduced the viscosity and density of the batter. The evaluation of the physicochemical properties of fortified cakes showed that the addition of HMT-UAH RS increased density, hardness, gradient, gumminess, and chewiness, while the specific volume, moisture content, cohesiveness, springiness, and resilience values were significantly decreased. Also, supplementation of cakes with HMT-UAH RS increased the L* value of crust and crumb of the cakes, whereas a* and b* values reduced. The results of the sensory evaluation showed that the addition of HMT-UAH RS up to 20% led to the preparation of cakes with acceptable sensory scores, especially with higher color liking scores.