| Gellan gum is a kind of novel polysaccharide with high commercial value and studies on its characterizations are of great significance. The world sale market is monopolized by a few foreign countries. The development of domestic high-acyl gellan gum industry is limited due to few relevant theory studies. Therefore, studies on its characterizations are instructive for the improvement of high-acyl gellan gum industry of our country. This work studied the properties of high-acyl gellan gum (HA gellan gum) and its application. The main contents and conclusions of this paper are listed as follows:Rheological properties of HA gellan gum were studied by steady and dynamic rheological test. The results showed that HA gellan gum solution behaved as pseudoplastic fluid with good shear thinning. The pseudoplasticity became more obvious when concentration increased. The apparent viscosity of HA gellan gum solution decreased with higher temperature. The solution approached Newtonian behavior at higher temperatures. The flow activation energy E of HA gellan gum decreased with higher shear rates. The apparent viscosity of HA gellan gum decreased slightly with lower pH. Weak gel formation occurred with addition of 0.01% Ca2+ and 0.1% K+. The G' of HA gellan gum became less frequency dependent with increasing gel concentration. The elasticity of HA gellan gum gel improved with addition of Ca2+. Viscoelasticity of HA gellan gum decreased due to electrostatic repulsion when the caution concentration was too high.The characterization of HA gellan gels were conducted by uniaxial compression, stress relaxation and creep test. The compression test showed that the Stress and ED of 0.3%-1.0% HA gellan gels increased with higher concentration. The strongest strength and stiffness were obtained at Ca2+ concentration of 0.05%-0.1%, K+ concentration of 0.4%-0.9%, Na+ concentration of 0.2%, respectively. The force relaxation curves of HA gellan gels were fitted well by the experiment model I. The initial decay rate of stress 1/k1 which depends on pore size of the gel network decreased with higher concentration. The residual stress which could be related to the degree of cross linking in the polymer network increased with higher concentration. The smallest 1/k1 and the highest Fe were obtained at Ca2+ concentration of 0.04%-0.06%, K+ concentration of 0.4%-0.8%, Na+ concentration of 0.2%, respectively. The creep test showed that the elasticity of HA gellan gel improved with higher concentration and the gel exhibited the best elasticity at Ca2+ concentration of 0.04%-0.09%, K+ concentration of 0.4%-0.9%, Na+ concentration of 0.2%, respectively. All three tests results showed that the gel properties were affected more by the gel concentration than the cation and the gel's texture properties were good in a cation range instead of a critical concentration.Studies on the water holding capacity(WHC) of HA gellan gum affected by gel concentration, cation concentration and high/low acyl gellan gum weight ratio showed that HA gellan gum exhibited great WHC. The water loss from HA gellan gels after 60 days storage at 4℃or being subjected to 2000r/min for 120min were only 2-3%, independent of calcium concentration. The content of low-acyl gellan gum had an obvious effect on the WHC of HA gellan gel. The worst WHC was observed at H/L=50/50. The NMR test showed that the relaxation time T2 became shorter with the increased HA gellan gum concentration.Studies on the effects of HA gellan gum on the stabilities of CMC-protein system was studied in terms ofζ-potential. Effects of different process technique and HA gellan gum concentration on pulp AMDs were also studied. The results showed that:0.03% HA gellan gum is helpful for the stability of CMC-protein.4 different technologies were designed, the results suggested that No.3 demonstrated the best effect. CMC has no suspension effect. HA gellan gum can improve the suspension of the pulp on the base of the existence of stabilizers such as CMC to protect the protein. The higher content of HA gellan gum resulted in higher viscosity and better suspension ability. Adding 0.02-0.03% HA gellan gum can make the pulp suspend well in the system, too much HA gellan gum would do harm to the taste of pulp AMDs. |
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