Research On Physical Properties Of Bacterial Cellulose

Bacterial cellulose (Bacterial Cellulose, BC) is a gelatinous membrane prepared byAcetobacterxylium and other microorganisms in liquid fermentation. Compared with plantfibers and animal fibers, it has several excellent characteristics, such as: nanoscale, ultrapure,high water content, better Young’s modulus and biology adaptability. Bacterial cellulose iswidely used in the food, paper, pharmaceutical and bio-chemical industry. To expand theapplications of bacterial cellulose, the microscopic morphology of bacterial cellulose wasobserved by scanning electron microscopy and atomic force microscopy. Then the texture,rheology and thermal properties of bacterial cellulose were studied by texture analyzer,rheometer and differential scanning calorimeter. And the effect of freezing and differentdrying methods on the texture and thermal properties of bacterial cellulose gel wasinvestigated in this paper. Based on the basic physical properties, the processing properties ofbacterial cellulose ribbon, such as thickener and clarifying agent, were studied in this paper.The main conclusions of this research were as follows:(1) The microfibrils of bacterial cellulose using vacuum freeze-drying presented loosenetwork structure. Howerver, the microfibril of bacterial cellulose using oven-drying waystightly combined and the loose network structure can’t been seen in SEM. Respectively, thecrystalline melting temperature of bacterial cellulose using vacuum freeze-drying andoven-drying were116.60℃and102.09℃, and the thermal degradation temperatures were374.35℃and372.39℃. So bacterial cellulose had good thermal stability.(2) the freeze-thaw stability of bacterial cellulose gel was superior to agar gel. Afreeze-thaw cycle had no significant effect on the hardness, springiness, gumminess andchewiness of nano-cellulose gel（P>0.05）. Furthermore, the hardness, gumminess andchewiness of bacterial cellulose gel increased with the increase of freeze-thaw cycles, aftertwo freeze-thaw cycles (P<0.05).(3) The consistency and index of viscosity of aqueous suspension of bacterial cellulosewere significantly higher than those of carboxymethyl cellulose solution. Additionally,whenthe concentration changed from0.4%to1.2%, a positive correlation was found between theconsistency and viscosity index of aqueous suspension of bacterial cellulose and theconcentration of bacterial cellulose (P<0.05); Under the condition of a relatively low shearrate(0.02～10S-1), the apparent viscosity of aqueous suspension of aqueous suspension of bacterial cellulose decreased with the increase of shear rate. On the contrary, under thecondition of the same shear rate, the apparent viscosity and shear stress of aqueous suspensionof bacterial cellulose increased with the increase of concentration of aqueous suspension ofbacterial cellulose. The suspension displayed a shear-thinning behavior, so the aqueoussuspension of bacterial cellulose was called as non-Newtonian fluid; The suspension appearedflow until the shear stress exceeding the yield stress and the values of shear stress werepositively related to the values of shear rate(P<0.05). So the aqueous suspension of bacterialcellulose was called as Bingham plastic fluid.(4) Adding a small amount of bacterial cellulose ribbon could significantly improve theconsistency and viscosity index of konjac solution (P<0.05), and bacterial cellulose andkonjac had synergistic thickening effect. Bacterial cellulose ribbon had a good clarifyingeffect on jujube wine, jujube vinegar, lactic acid drink of jujube and hovenia vinegar. Sobacterial cellulose ribbon can be used as thickener and clarifying agent.