Effect of ultrasound on mill starch and protein in ultrasound-assisted laboratory-scale corn wet-milling
2021
Liu, Jie | Yu, Xiaoshuai | Liu, Yawei
Ultrasound was applied to facilitate starch-protein separation during ultrasound-assisted laboratory-scale corn wet-milling. The effects of ultrasound on the properties of mill starch and protein were investigated to explore the possible mechanisms in this study. A higher starch yield was obtained with sonication treatment in starch-protein separation (15 min, 200 W) and the results showed that ultrasound did not induce damage to the product starch. The differences in the distribution of water proton transverse relaxation time for mill starch suggested that the interaction between starch granules and protein in mill starch was destroyed. The free sulfhydryl content increased by 37.21% and the disulfide bond content decreased by 43.66% of the separated proteins indicated that ultrasound destroyed the disulfide bonds effectively (p < 0.05). Sonication treatment for longer time or at higher power decreased α-helix and β-turn while increased β-sheet and random coil (p < 0.05). Ultrasound increased surface hydrophobicity and decreased the thermal stability of the protein (p < 0.05). The higher intensity of ultraviolet–visible spectroscopy and ultraviolet-difference absorption spectroscopy indicated the unfolding of protein by sonication treatments. Ultrasound may break down the disulfide bonds and hydrogen bonds of protein molecules, effectively releasing starch from the disintegrated protein agglomerates.
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