Effects of ultrasonic on structure, chain conformation and morphology of pectin extracted from Premna microphylla Turcz

In this study, ultrasonic effects on structure, chain conformation and morphology of pectin extracted from Premna microphylla Turcz (PEP) and its probable mechanism were investigated. In the process of ultrasonic treatments, the chains of PEP were fractured rapidly within the initial 10 min and then the degradation rate gradually slowed down. The primary structure of PEP nearly remained unchanged after ultrasonic degradation. The rigid semi-flexible chains of PEP were converted into flexible chains, flexible coils, even compact coils. Sonication at low intensity for short time made PEP molecular chains curly collapse and tighten up. Long duration sonication at high intensity generated excessive small rigidness segments that mutually aggregated because of hydrogen bonds and inhibited the self-coiling of PEP chains. Atomic force microscopy (AFM) analysis supported the conformation transition of PEP chains. The results provided a fundamental basis for orientation design and process control of PEP structure.