| Carrageenan (Carrageenan, which is also called the antlers algin or carrageenin) isa red algae polysaccharide mixture with great economic value, which is extractedfrom red algae such as chondrus, eucheuma, gigartina and hypena. In recent years,Due to using the gelatin as main raw materials, animal drug packagings is showingmore and more drawbacks in security and timeliness. So that there is an increasedemand of eucheum acottonii carrageenan, who is as one of the raw materials ofbotanical drug packaging shell. The market share of carrageenan currently hasreached80%or more in drug packaging industry, so the production of carrageenanwhich is suitable for drug packaging raw materials has great potential in the market.Traditionally most carrageenan production methods are used sodium hydroxide andpotassium chloride, but this would cause the viscosity of carrageenan greater than130mPa·s, and the sulfate group content greater than25%, which limit the developmentof carrageenan in film-forming of drug packaging. And in the course of alkalitreatment, due to the use of the highly water-soluble KCl, which caused the potassiumcan’t completely penetrate into the internal structure of eucheuma acottonii, andunable to prevent dissolution of the small molecule carrageenan effectively, resultingin more and more carrageenan to stay in the lyeand, which cause decline ofcarrageenan yield, and the waste lye can’t be reused again. While treated eucheumaacottonii with potassium hydroxide, K-and OH-can get into the internal structure ofeucheuma at the same time, which carrageenan dissolution can be preventedeffectively. In this way, not only the yield and the gel strength have been effectivelyimproved, and the viscosity and sulfuric acid group of carrageenan also greatlyreduced. Due to the waste lye can be reused, reducing the cost of the carrageenan. Allof these overcome the defects of NaOH-KCl in the process of preparation ofcarrageenan.Carrageenan is widely used in the field of food, daily chemical and pharmaceutical for its good stability, gel strength, viscous and complex performance. All above theseapplications of carrageenan have a close relationship with its rheological properties,thus it has an important significance for carrageenan of its further development andapplication to grasp the rheological properties and its variation under variousconditions accurately.This paper mainly studies the extraction of carrageenan from eucheume cottoni, ofwhich alkali-treatment process is used potassium hydroxide instead of sodiumhydroxide, eventually obtained carrageenan of high yield, high gel strength, lowviscosity and low sulfate group content. And compared this carrageenan withcarrageenan which is obtained under the traditional process on various indicators andrheological feature, the research results are as followed:1. Single factor of alkali treatment concentration, alkali treatment temperature,alkali processing time were done to study the conditions affected the arrageenan of itsyield, gel strength, viscosity and sulfate group, to conform the best area of everyfactor. By orthogonal experiments, to confirm the influence degree of various factorsfrom big to small in turn is:alkali treatment temperature>alkali treatmentconcentration>alkali processing time, the optimal parameters were established: alkaliconsistency13%, treatment temperature85℃and treatment time3.5h.2. Under the same instrument and experimental conditions, eucheume cottonii werealkali-treated with KOH and NaOH-KCl conditions, carrageenan technical indicatorsof yield, gel strength, viscosity,sulfate group and transparence were compared, andfound that carrageenan which is alkali-treated with KOH is significantly reduced inviscosity and the sulfuric acid group and the yield and transparency also increased,and the gel strength is relatively little difference. Ultimately we obtain thecarrageenan which viscosity is less than60mPa s, and the sulfate group content lessthan22%, and the quality of the carrageenan is improved.3. Compared to their rheological properties, we can find that in the same shear rate,both alkali treating KOH and NaOH-KCl carrageenan solutions of its viscosity areincreased with decreasing concentration, two carrageenan solutions weredemonstrated shear thinning nature and extent of both pseudoplastic are increased with increasing carrageenan concentration. However, it can be seen by comparison,obtained by treatment with KOH carrageenan, the flow index is close to1, and theconsistency index carrageenan treated variation amplitude is small than theNaOH-KCl, indicating that for the same concentrations of two carrageenan solutions,treated with KOH solution obtained carrageenan shear thinning is more difficult, morelikely to exhibit Newtonian properties. The viscosity of two carrageenan decreased asthe increasing temperature. The thixotropic of arrageenan treated with KOH is smallcompared NaOH-KCl. Frequency inc Treated with KOH to obtain its thixotropiccarrageenan small compared NaOH-KCl. With the increasing frequency shear, KOHand NaOH-KCl alkali carrageenan G ’and G "are increased, but at low frequencies G’is greater than G", the system dominated by viscous, when the frequency increases toa certain value after the G ’is less than G ", the system dominated by elastic, showinga weak glue. In addition, both the kinematic viscosity carrageenan solutions η’ aredecreased with increasing frequency, and have shown the shear-thinningcharacteristics. Wherein the alkali treatment with NaOH-KCl loss of carrageenanobtained modulus G" representing the amplitude variation carrageenan large KOHtreatment, treatment with KOH carrageenan obtained kinematic viscosity η’representing changes NaOH-KCl treatment carrageenan amplitude is small, and themeasurement results of the static low rheology of low viscosity carrageenan sulfateresults. |
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