Effects of Ultrasonication on the Conformational, Microstructural, and Antioxidant Properties of Konjac Glucomannan

Abstract

This study aims to evaluate the effects of ultrasonication (US) on the conformational, microstructural, and antioxidant properties of konjac glucomannan (KGM). US treatment with a 20-kHz and 750-W ultrasonic processor at 60% amplitude was applied for partial degradation of KGM with an average molecular weight (MW) of 823.4 kDa. Results indicated that the US treatment caused dramatic reduction in the MW, apparent viscosity, hydrodynamic radius, and z-average mean radius of gyration. The flexibility of chain conformation of native KGM was slightly increased during the US treatment. According to electronic microscopic imaging, the compact, smooth, and orderly fibrous strings formed by KGM were changed to amorphous, porous flakes and globular particles after US treatment. KGM and its US-treated fractions showed moderate radical-scavenging and ferric-reducing antioxidant activity. US degradation of KGM affected these activities either positively or negatively, depending on the US treatment period. In summary, ultrasonic degradation of KGM caused changes in its conformation characteristics, microstructure, and antioxidant activities.

Preparation and characterization of konjac glucomannan (KGM) and deacetylated KGM (Da‐KGM) obtained by sonication

“…6(A)), which was consistent with previous studies concerning KGM. 3,8,13,14,19 Based on Craessley's theory, the shear-thinning behavior of KGM or Da-KGM solutions could be explained by the disruption of the entangled polysaccharide molecule network. 31 Briefly, at the low shear rate, disruption of interactions was balanced by the formation of new ones, resulting in a constant apparent viscosity; at the high shear rate, disruption of those entanglements predominated and the molecules aligned in the direction of the flow, leading to the observed decrease in apparent viscosity.…”

“…12 The ultrasonic degradation effect on KGM in aqueous solution has been widely reported: sonication of KGM solution caused a dramatic reduction in viscosity and molecular weight, but little destruction of the primary structure. 8,13,14 It was supposed that power ultrasound could weaken the intermolecular interactions in KGM molecules as well as the intramolecular interactions in the KGM polymer chains in aqueous solution, leading to the degradation of KGM. 15 Alcohols, as non-solvent, influence the thermodynamic quality of the solvent, thus affecting solubility and intermolecular associations of food polysaccharide.…”

Degradation of Exopolysaccharides from Lactic Acid Bacteria by Thermal, Chemical, Enzymatic and Ultrasound Stresses

“…Studies point to unaltered structures after ultrasonication, however, in some studies, the FT-IR measurements might not have been sensitive enough to detect minor changes of EPS structure [ 28 , 30 , 44 , 50 , 51 ]. The random chain scission was proved for the majority of polysaccharides, e.g., chitosan [ 36 ], konjak glucomannan [ 26 , 33 ], pectin [ 51 ], (1-3)(1-6)-α-D-glucans from Leuconostoc citreum [ 21 ] or polysaccharides from Sargassum pallidum [ 50 ]. For some polysaccharides, such as carboxylic curdlan [ 28 ] and six different dextrans from L. mesenteroides [ 27 ], however, midpoint chain scission was observed, which is in contrast to our study, where dextran also fitted the random chain scission model.…”

“…Polymer degradation mostly follows first- or second-order kinetics [ 22 , 31 , 33 ]. For a correct estimation of ultrasound-induced EPS degradation, it is necessary to know about the chain scission mechanism.…”

High-Intensity Low-Frequency Ultrasonic Treatment of Sulfated Polysaccharide from Brown Algae

“…Ультразвуковая обработка приводит к снижению молекулярной массы и вязкости раствора полимера, но не сопровождается значительным изменениям химической структуры [32,33]. При этом разрыв полимерной цепи осуществляется, как правило, в центральной точке или в самых слабых местах структуры, и скорость разложения увеличивается с ростом молекулярной массы полимера [33]. В целом, преимущество метода ультразвукового обработки заключается в его быстроте, мягкости и экологичности [34].…”