Aijun Hu

Different‐frequency ultrasonic effects on properties and structure of corn starch

BACKGROUND Ultrasound is widely used to accelerate many reactions and unit operations, but few studies have reported its effects on starch properties and structure. RESULTS Corn starch suspended in ethanol solution was treated by dual-frequency ultrasound (DFU) and single-frequency ultrasound (SFU). Results showed that the transparency of the starch treated under 20 + 25 kHz DFU improved by 26.94% and 31.70%, respectively, compared to 20 kHz and 25 kHz SFU. Hardness, brittleness, elasticity, adhesiveness, conglutination degree, chewiness and recoverability of starch was reduced after ultrasonic treatment, and with increasing ultrasonic frequency these properties decreased. Its enthalpy value also decreased with ultrasound. Compared with each SFU treatment, enthalpy value decreased by 1.41% and 0.82%, respectively, by DFU. The freeze-thaw stability of starch was also weakened by ultrasound, which was obviously changed by DFU. Under ultrasound, the crystal structure of starch was not damaged, characteristic diffraction peak intensity was significantly reduced and diffuse diffraction features increased, exhibiting a decline in crystal lattice ordering degree. In comparison to SFU, DFU caused a pronounced reduction in starch crystallinity. CONCLUSION After ultrasonic treatment, the transparency of corn starch paste improved, but its hardness, brittleness, elasticity, adhesiveness, conglutination degree, chewiness and recoverability decreased, as well as starch crystallinity and enthalpy values. DFU was found to be more effective than SFU.

Effect of Ultrasound on Lysine Muriate Crystallization

Ultrasound was applied to the crystallization process of lysine muriate solution. The effects on crystal yield of lysine muriate were investigated, including ultrasonic time, ultrasonic power, and crystallization time. The experimental results showed that the crystal yield reached 84.08 % with the adequate conditions of ultrasonic power 112 W, ultrasonic time 50 min, and crystallization time 5 h. And the effects of ultrasonic power on the nucleation induction period and crystal appearance of lysine muriate were also researched, the results indicated that with ultrasound, induction period was shortened significantly compared to that without it at the same supersaturation ratio. The higher the ultrasonic power, the shorter the induction period, and the smaller the crystals. With the increase of ultrasonic power, the crystals became smaller and more uniform. It can be concluded that using ultrasound-assisted crystallization cannot only improve the crystallization rate and crystal yield, but also obtain crystalline product with the characteristics of small particles and uniform distribution by controlling ultrasonic power.

Effects of Dual-Frequency Ultrasound with α-amylase on the Properties and Structure of Mung Bean Starch

In this paper, we focus on the effects of dual-frequency ultrasound (40 and 80 kHz) with α-amylases (5U/g) on the properties and structure of mung bean starch. The reducing sugar value and starch solubility in the treated starch slurry under ultrasound enzyme were studied. Scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR) were used to measure the apparent structure and crystal texture of starch. The results indicated that compared with the results of single-frequency ultrasound treatment, dual-frequency ultrasound promoted the starch hydrolysis by amylase and increased the starch solubility remarkably. More channels and holes were found on the surface of treated starch granule by SEM. The results of FTIR analysis showed the FTIR peak shape of ultrasonic treated starch was different from that of the control starch.

Soybean Peptide Preparation by Enzymatic Hydrolysis with and without Ultrasound

Soybean protein powder and alkaline alcalase protease were taken as raw materials, and the effects of ultrasonic power, pH, substrate concentration，enzyme dosage , and temperature on soybean protein hydrolysis degree (DH) and DH increment percentage were studied with and without ultrasound in this paper. The results indicated that efficiency of ultrasound depended on its power. The ultrasound of 40kHz, 96W enhanced remarkably the enzymatic hydrolysis of soybean protein. Compared with those under no ultrasonic, the curve trend of relation between DH and pH, substrate concentration, enzyme dosage or temperature was not changed by ultrasound, and the optimal temperature, pH also kept the same, which was 55℃, pH8.5 respectively, however, the DH increased evidently with ultrasound