Study On The Property Of Konjac-Artemisia Songarica Schrenk Gum Composite System

Network structure formed by non-covalent bond in konjac gum (KGM) is not stable, thus leading to a poor storability. KGM has stable network structure formed by covalent bond when prepared under the condition of strong base (pH 11～12), but this is not good for its application on food industry. The property of KGM can be improved by using KGM to mix with natural hydrophilic food gum. Therefore, it is essential to develop new polysaccharide which can have complex synergism effect mixing with KGM. ASKG has a strong complexing and bonding ability, excellent chemical stability, and high potential to absorb water for swelling. Additionally, ASKG possesses many special nutrition dietary functions. The paper was focused on the mixture of KGM and ASKG. The complex synergism effect between KGM and ASKG and the texture properties, rheological properties and stucture properties of compounded system were analyzed. The optimum process parameters to prepare the complex sol and the complex gel were given. And the structure -activity relationship of the system was also discussed. The results were concluded as follows:(1)Study on the property of the complex sol The change of concentration and viscosity of KGM and ASKG had the power function relationship. The mixture of them showed complex synergism effect and the viscosity was the biggest when KGM accounted for 80% of the compounded system. The factors which had effect on the apparent viscosity of mixture sol were in the order of concentration, ratio, mixing time and temperature. The optimized process parameters were KGM ratio 90%, concentration 11g/L, temperature 75 ℃, mixing time 40min. The theoretical viscosity of the complex sol under this condition was 22898.58 mPa.s.(2)Study on the property of the complex gel Hardness, adhesiveness and flexibility of the complex gel were improved to some extent by adding a small proportion of ASKG to KGM gel. Both lower and higher temperature had negative effect on the stability of the gel system. With the increase of concentration of polysaccharide in compounded system, the complex gel had stronger hardness and weaker flexibility. The action of mechanical stir force in appropriate time had contributed to the entanglement among the molecular chains in macromolecule materials such as KGM and ASKG. However, long stirring would destroy hydrogen bonds among the molecular chains, thus reducing the stability of the complex gel. The hardness of the complex gel was improved as the alkali concentration rising, but the lower alkali concentration had a little effect on the texture characteristics of the complex gel, The suitable concentration of salt ionic concentration was beneficial to entanglement among the molecular chains.The optimized process parameters of KGM-ASKG complex gel were: KGM/ASKG application 8:2, concentration 40g/L, gel temperature 75℃, stirring time 60 min, salt ionic concentration 0.06 mol/L.(3)The rheological properties of compounded system The constitutive relation of compounded system were characterized by means of Cross equation and its accuracy was quite high.In the equation, the dimensionless constant m<1. The compounded system showed shear thinning. With the content of KGM in the system rising, intermolecular force was enhanced and the tend to shear thinning was also obvious. By comparing parameter m. it could be found that the non-Newtonian behaviour of ASKG was weaker than that of KGM.The concentration range of changing between sol and gel was 12～15 g/L. Increasing temperature could reduce intermolecular force of the system. When the concentration raised to 9 g/L, the change of modulus was not obvious with temperature increasing. The modulu began to soar slightly when the temperature reached to 85 ℃ at relatively high concentration (9-18 g/L). The sensitivity degree of the molecular chains in KGM to temperature was higher than that of ASKG.(4)The structure and physicochemical properties of KGM/ASKG compounded systemKGM gel, ASKG gel and the mixture gel existed in unshapen a structure form. No new crystalline region was formed during the process of compounding. The gel structure of compounded system was much more stable, the internal free space expanded and interaction between hydrophilic group and water enhanced. And the stability of complex gel was better than single gel. No functional groups were produced and disappeared obviously in the gel formation process. Hydrogen bond formed between KGM and ASKG, and the number of the hydrogen bond was the largest when the ratio of KGM to ASKG was 8:2. Hydrogen bond was the most important driver of maintaining network structure of gel. With the increase proportion of KGM in the compounded system, the gel presented dendrite or fishbone structure. The compounded system (KGM: ASKG=8:2) was similar to KGM, the aperture became small and microstructure was even more compact. This morphology feature was consistent with the results of the rheological properties.