7/25/2019 biochemistry carbohydrates

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Crystallinity and thermal properties of different celluloses and starches

T. Perko, M.Škerget, Ž. KnezUniversity of Maribor, Faculty of Cheistry an! Cheical "ngineering, #aboratory for

$e%aration Processes an! Pro!uct &esign, $etanova '(, $)*+ Maribor, $lovenia- tel./01 +++ 23 31/, fa45 /01 ++6 +( ((3, e*ail5 o7ca.skerget8uni*b.si

 9atural %olyers are i%ortant aterials for in!ustrial use, an! they usually refer to %roteins, %olysacchari!es an! late4. They are use! because their :ater !is%ersions are bio!egra!able an! have ability of thickening an! of foring /& structures even at very lo:concentrations. For %rocessing the %olyers, su%ercritical flui!s, es%ecially C;+, are very

 %roising. $u%ercritical carbon !io4i!e <scC;+= is clean an! versatile solvent. )t is non*to4ic,non*flaable, cheically inert, environentally safe an! ine4%ensive. )t is a goo! solventfor any lo: olecular :eight co%oun!s an! a fe: %olyers but it is generally a very %oor solvent for high olecular :eight %olyers. ;n the other han!, C;+ is relatively goo! solublein several %olyers an! can therefore be use! as %rocessing e!ia instea! of conventionalsolvents.

)n %resent :ork follo:ing carbohy!rates have been stu!ie!5 aize starch, :heatstarch, starch, ethyl cellulose, carbo4yethyl cellulose :ith three !ifferent olecular :eights  <M:>2., M: >+6. an! M: >(.= an! cellulose acetate %hthalate. Thisthero reversible hy!rogels are very interesting !ue to the fact that they are naturally !erive!an! are abun!antly %resente! on "arth. For stu!ying the functional grou% o!ifications!uring !ifferent treatents of the sa%les the FT)? etho! :as use!. The structure of the

 %olyer an! the !egree of crystallinity :as analyze! by @AB&, :hile &$C, TA an! $&TA

:ere use! to !eterine the theral behavior of the %olysacchari!es. &$C can easure thegelatinization transition te%eratures, i.e. onset <T o=, %eak <T  p=, conclusion <T c= te%eratures,enthal%y <D H  g = of gelatinization an! s%ecific heat ca%acity <C  p=. For this %ur%ose, a :i!e rangeof %olyer concentrations fro .'+6E'.(6 :t :ere %re%are! :ith !eionize! :ater. The

 %artially !issolve! sa%les :ere %ut into a refrigerator an! ke%t for +3 h before use.Furtherore, %ure sa%les :ere e4%ose! to C;+  at s%ecific con!itions <%ressure,

te%erature, tie, C;+  release rate= an! above entione! analyses :ere re%eate! an!co%are! to those obtaine! for non*treate! sa%les.

Key words: cellulose, starch, &$C, TA, FT)?, @AB&, $&TA