•Three potential factors were investigated to control ice crystal growth during aerogel formation.•Low temperature polarizing microscopy and scanning electron microscopy were used to view the ice ...crystal and pore structures.•Size distribution figures of ice crystals and aerogel pores were drawn and could be used to support the discussions.
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.
Konjac glucomannan (KGM)/ethyl cellulose (EC) blend films were prepared at different blend ratios (KGM/EC = 10/0, 9/1, 8/2, 7/3, 6/4, and 0/10, w/w) in the presence of dibutyl sebacate at 25% (w/w) ...of total solids content.
Hydrogen bond interactions between KGM and EC occurred. An ethyl cellulose phase consisting of oval-shaped particles was uniformly embedded in the KGM continuous phase. The maximum values of tensile strength and elongation at break of blend films were respectively 48 MPa and 12.7% when the ratio of KGM and EC was 7/3 (w/w). Compared to KGM film, the moisture resistance, thermal stability, tensile strength, and elongation at break of blend films were increased. In addition, water vapor transmission was decreased, but the oxygen permeability was increased by blending. Applications of the blend film of KGM and EC for food packaging are suggested.
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•Films based on konjac glucomannan and ethyl cellulose were prepared and characterized.•Blend films were composed of the KGM continuous phase with oval-shaped EC particles embedded in films.•Increased contents of konjac glucomannan affected film forming properties.
•Carboxymethyl konjac glucomannan (CMKGM) and soy protein isolate (SPI) were used.•Blended films of CMKGM and SPI were prepared.•Hydrogen bonding and Maillard reactions explain CMKGM and SPI ...interations.•Biopolymer interactions led to improved properties of the blended films.•Tensile strength and elongation at break were greater in the 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.
In this paper, konjac glucomannan (KGM) and zein nanoparticles (NZ) were used as film-forming substrates, and the KGM/NZ blend films (KNZ) were prepared by solution casting. The microstructure, ...thermal, mechanical, hydrophobic and barrier properties of KNZ were investigated at different drying temperatures (30, 40, 50, 60, 70, 80 ℃). The results showed that when dried at 40, 50, 60 ℃, KGM and NZ had good compatibility and NZ was uniformly dispersed in KGM matrix, the microstructure of KNZ was denser and its mechanical and hydrophobic properties were enhanced significantly (P<0.05). When the drying temperature was 40 ℃, KNZ showed the best performance, such as the highest thermal decomposition temperature (334.6 ℃) and tensile strength (79.27 MPa), the smallest solubility (19.99%) and water vapor permeability (7.641×10−13 g·cm/(cm2·s·Pa)). The information obtained would provide a reference for the development and application of KNZ as a packaging material.
Moisture retaining materials are widely used in the food, cosmetic and tobacco industries. Conventional materials, for example, glycerin and propylene glycol have reasonable moisture absorption ...abilities, but poor moisture retention. Konjac glucomannan (KGM) is a heteropolysaccharide made up of glucose and mannose, linked with β-1,4 glycosidic bonds. Konjac superabsorbent polymer (KSAP) is a derivative containing hydrophilic groups and a network structure prepared by grafting sodium acrylate on to KGM. Previous work has shown that KGM and KSAP have properties which can lower water activity (a
w). The objective of this paper is to consider the mechanism of this process. Filter-paper is used as a model fiber instead of tobacco, where this effect is practically important. Moisture absorption and retention of KGM and KSAP are compared with glycerin and propylene glycol. Moisture desorption isotherms have been determined and fitted to the GAB model. The results show that the moisture retention of KGM and KSAP are better than propylene glycol and glycerol. At a given moisture content, a
w of filter-paper containing KSAP was the lowest. The monolayer moisture content and net isosteric heat of desorption of filter-paper containing KGM and KSAP were greater than that of the control groups. This study demonstrated that KGM and KSAP have the potential to be used as moisture retaining ingredients.
Display omitted The moisture desorption data for filter-paper with and without humectants at several temperatures (5
°C, 22
°C, and 40
°C) are shown in this figure. The moisture content increased when a
w increased in all the systems studied. The filter-paper containing humectants had more moisture compared to the control group. In addition, the filter-paper with KGM and KSAP contained more equilibrium moisture than the glycerin samples. In the low a
w range, the moisture content of samples contained KGM and KSAP increased faster then the control groups. It is suggested that adding KGM and KSAP changed the distribution of water in the filter-paper, increased the monolayer moisture content, and led to a more solid water combination.
•Good film-forming compatibility was achieved between hydrophilic KGM and hydrophobic zein molecules.•FTIR and X-ray results supported existence of strong intermolecular interactions in the blend ...films.•Aggregated zein were homogeneously dispersed in KGM continuous matrix.
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.
•Zein promoted the aggregation of KGM chains in KGM/zein blend solution.•Zein particles grew larger but were homogeneously distributed during drying.•KGM/zein blend solution gradually formed a weak ...gel after 2 h of drying at 60 °C.
During film formation at 60 °C, the microstructure and rheological properties of konjac glucomannan (KGM) film-forming solution and KGM/zein blend film-forming solution were investigated. The drying process of film-forming solutions was divided into two stages according to the drying curves. Scanning electron microscopy showed that KGM chains in the blend solution aggregated into thicker chains and formed a molecular network with larger pores. Zein particles grew larger but were homogeneously distributed during drying as observed by confocal laser scanning microscopy. The addition of zein improved the thermal stability of the film-forming solution. As the drying proceeded (up to 8 h), KGM solution exhibited a typical concentrated solution behavior due to molecular entanglement; whereas the blend solution gradually formed a weak gel after 2 h. Complex viscosity data for the film-forming solutions were well-fitted by the power-law model. The information obtained from the study is important for understanding the film-forming mechanism.
