Man Xiao

Interactions between carboxymethyl konjac glucomannan and soy protein isolate in blended films

To elucidate biopolymer interactions between carboxymethyl konjac glucomannan (CMKGM) and soy protein isolate (SPI) in different ratios on physicochemical properties of the blended films, biodegradable CMKGM/SPI films were prepared and characterized. The results showed that CMKGM and SPI are highly compatible in blended film formation, and that Maillard reactions and hydrogen bonds interactions between CMKGM and SPI occurred. The water adsorption of the CMKGM/SPI films progressively decreased with increasing CMKGM level, the surface wettability of the blended films was improved with increasing CMKGM content; the CMKGM/SPI blend films had enhanced tensile strength (TS) and elongation at break (EAB) compared to pure CMKGM and SPI films; the oxygen permeability of blend films was decreased; the roughness was decreased with increasing CMKGM content. Moreover, the CMKGM/SPI film was biocompatible and biodegradable.

Carboxymethyl modification of konjac glucomannan affects water binding properties.

The water binding properties of konjac glucomannan (KGM) and carboxymethyl konjac glucomannan (CMKGM) are important for their application in food, pharmaceutical, and chemical engineering fields. The equilibrium moisture content of CMKGM was lower than that of KGM at the relative humidity in the range 30-95% at 25°C. The water absorption and solubility of CMKGM in water solution were lower than that of KGM at 25°C. Carboxymethyl modification of KGM reduces the water adsorption, absorption, and solubility. Both carboxymethylation and deacetylation could confer hydrophobicity for CMKGM. These data provide the basis for expanding CMKGM application.

Characterization of konjac glucomannan-ethyl cellulose film formation via microscopy.

Konjac glucomannan-ethyl cellulose (KGM-EC, 7:3, w/w) blended film shows good mechanical and moisture resistance properties. To better understand the basis for the KGM-EC film formation, optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used to observe the formation of the film from emulsion. Optical microscopy images showed that EC oil droplets were homogeneously dispersed in KGM water phase without obviously coalescence throughout the entire drying process. SEM images showed the surface and cross-sectional structures of samples maintained continuous and homogeneous appearance from the emulsion to dried film. AFM images indicated that KGM molecules entangled EC molecules in the emulsion. Interactions between KGM and EC improved the stability of KGM-EC emulsion, and contributed to uniformed structures of film formation. Based on these output information, a schematic model was built to elucidate KGM-EC film-forming process.

The control of ice crystal growth and effect on porous structure of konjac glucomannan-based aerogels.

Konjac glucomannan (KGM)-based aerogels were prepared using a combination of sol-gel and freeze-drying methods. Preparation conditions were chosen to control ice crystal growth and aerogel structure formation. The ice crystals formed during pre-freezing were observed by low temperature polarizing microscopy, and images of aerogel pores were obtained by scanning electron microscopy. The size of ice crystals were calculated and size distribution maps were drawn, and similarly for aerogel pores. Results showed that ice crystal growth and aerogel pore sizes may be controlled by varying pre-freezing temperatures, KGM concentration and glyceryl monostearate concentration. The impact of pre-freezing temperatures on ice crystal growth was explained as combining ice crystal growth rate with nucleation rate, while the impacts of KGM and glyceryl monostearate concentration on ice crystal growth were interpreted based on their influences on sol network structure.

Structural characterization and properties of konjac glucomannan and zein blend films

A series of konjac glucomannan (KGM)/zein blend films were successfully prepared with zein in proportions 0-30%. The hydrophobicity of blend films were significantly stronger than pure KGM film, indicated by increased contact angle, swelling and solubility properties, and moisture absorption. Moreover, other properties including mechanical, thermal, water vapor and oxygen barrier were also found to be increased. FTIR indicated that hydrogen bond interactions and Maillard reaction occurred between KGM and zein molecules, and microstructural observations indicated that the aggregated zein was homogeneously dispersed in the KGM continuous matrix. However, these zein aggregations were larger with increased proportion of zein, leading to weakened molecular interactions with zein proportion >10%. A mixing ratio of KGM:zein=9:1 was suggested to provide best film properties. This research offers an alternative improvement for KGM-based biodegradable films.

Thermal conductivity, structure and mechanical properties of konjac glucomannan/starch based aerogel strengthened by wheat straw

This study presents the preparation and property characterization of a konjac glucomannan (KGM)/starch based aerogel as a thermal insulation material. Wheat straw powders (a kind of agricultural waste) and starch are used to enhance aerogel physical properties such as mechanical strength and pore size distribution. Aerogel samples were made using environmentally friendly sol-gel and freeze drying methods. Results show that starch addition could strengthen the mechanical strength of aerogel significantly, and wheat straw addition could decrease aerogel pore size due to its special micron-cavity structure, with appropriate gelatin addition as the stabilizer. The aerogel formula was optimized to achieve lowest thermal conductivity and good thermal stability. Within the experimental range, aerogel with the optimized formula had a thermal conductivity 0.04641 Wm-1 K-1, a compression modulus 67.5 kPa and an elasticity 0.27. The results demonstrate the high potential of KGM/starch based aerogels enhanced with wheat straw for application in thermal insulation.