Effects of high power ultrasound on the enzymolysis and structures of sweet potato starch

Abstract

BACKGROUNDThe general enzymatic method for producing reducing sugar is liquefaction followed by saccharification of starch. This method results in lower yields, consuming high energy and time. Therefore, the present study evaluated a new approach for producing reducing sugar from sweet potato starch (SPS), including simultaneous liquefaction (by α‐amylase) and saccharification (by glucoamylase) of SPS pretreated with high power ultrasound. The effects of ultrasound parameters on the conversion rate of SPS and mechanism were investigated.RESULTSThe optimum ultrasound pretreatment conditions were a frequency of 20 kHz, SPS concentration of 125 g L−1, temperature of 30 °C, pulsed on‐time of 3 s, pulsed off‐time of 5 s, power density of 8 W mL−1 and sonication time of 15 min. The ultrasound assisted enzymolysis resulted in a SPS conversion rate of 59.10%, which was improved by 56.35% compared to the control. The results of pasting properties and thermal analysis showed that ultrasound pretreatment decreased the peak viscosity, breakdown temperature, setback viscosity, gelatinization range (TC − TO) and enthalpy of gelatinization (ΔH) of SPS significantly (P < 0.05) by 12.1%, 7.6%, 6.6%, 18.8% and 44.4%, respectively. Fourier‐transform infrared spectroscopy indicated that ultrasound damaged the ordered structures and crystallization zone. This was confirmed by X‐ray diffraction analysis, which showed that the relative crystallinity was reduced by 15.0%. Scanning electron microscopy showed that ultrasound destroyed the surfaces and the linkages between starch granules.CONCLUSIONPrior to simultaneous liquefaction and saccharification of SPS, high power ultrasound pretreatment is a promising method for improving the conversion rate of starch. © 2020 Society of Chemical Industry

Isothermal and temperature-cycling retrogradation of high-amylose corn starch: Impact of sonication on its structural and retrogradation properties

“…Sonication converted the B-type diffraction pattern of native starch to a C-type diffraction pattern, which consisted of a mixture of A- and B-type crystallites, resulting in a significant ( p < 0.05) decrease in the relative crystallinity of sonicated starch in both the raw and gelatinized states. The significant decrease in crystalline peaks corresponded with previous studies [22] , [46] . After lyophilization following gelatinization, both non-sonicated and sonicated starches showed similar X-ray patterns of typical amorphous curves from gelatinized starch, with blunt peaks at 17.2°, 20°, and 23° ( Fig.…”

Extraction and modification of Achachairu's seed (Garcinia humilis) starch using high‐intensity low‐frequency ultrasound

“…Depending on the intensity, ultrasound treatment can rupture the link between starch granules and, consequently, reduce the average size of the granules. The consequent increase in the surface area could increase the rate of enzymatic hydrolysis (Jin et al, 2020).…”

“…The consequent increase in the surface area could increase the rate of enzymatic hydrolysis (Jin et al, 2020).…”

White sorghum landrace and corn starches in glucose syrups production using enzymatic and acid amylolysis

“…(2013). Also, the rates of enzymatic reactions are closely related to diffusion in high‐viscosity aqueous solutions (Cicerone & Soles, 2004; Jin et al., 2020). However, diffusion would be hindered by the relatively low mobility of water molecules in the reaction system.…”