Fractionation of StarchReferences:Chapter 14, Commercial separation of amylose and amylopectin from starch, Starch Production Technology, edited by J.A. Radley.Chapter 8, Fractionation of starch, Austin H. Young, Starch: Chemistry and Technology, edited by R.Y Whistler.
Amylose VS AmylopectinMolecular size
Methods of Fractionation Aqueous leaching of gelatinized granules
Dispersion of the granule and fractionation with complexing agents (selective precipitation)
Fractionation by retrogradation
Fractional precipitation (salting out)
Raw MaterialsCereal starches have a great disadvantage as a raw materials because they have a high content of fatty compounds.
Potato starch is very suitable for fractionation process, for it contains no fatty substances. The phosphate groups, bound only to the amylopectin molecules, increase the difference between both starch components.
Waxy starches contain practically no amylose, so that it is not necessary to fractionate them.
Amylomaize can be subjected to fractionation.
Aqueous leaching of gelatinized granules Leaching occurs from swelling starch granules in water at temperatures of 57 100 C. Mobile amylose molecules diffuse out of the swallen granule while the granule is intact.
Most of the amylopectin remains H-bonded or crystallized in the granule residue.
25 g starch + 25 ml cold waterAdd slowly with stirring 150 ml of water at 80 CMaintain at 70 C for 5 minsPour into 1200 ml of water at 60 CStir very slowly at this temperature for 4 h(avoid rupture of the swollen granule)Cool, centrifugeSupernatant amyloseGelatineous depositamylopectinRef:
SupernatantGelatineous depositAdd methanol into supernatant (to get 20% alcohol solution)precipitatecentrifugeGrind precipitates in mortar with 95% ethanolFilter and dry in vacuum ovenAmylose Grind in mortar with 95% ethanolFilter and dry in vacuum ovenAmylopectin
defatting starch geanules by heating in aqueous methanol enhances leaching of the amylose. (useful for starch which strongly resists swelling and gelatinization.
removal of oxygen from the water reduced degradation of starch.
low temperature pretreatment of granules induces further crystallization, resulting in higher yield of extraction without granule rupture. (for example; froze at -78 C for 1 min)
Dispersion of the granule and fractionationwith complexing agents (selective precipitation)
DefattationDispersionInclusion complex formationSeparation of complex
Ref: Schoch T.J., 1941
Defatting procedureReflux the starches for several hours with 85% methanol. After five extractions the lipids are sufficiently removed.DispersionDisperse 1-3% of starch in water at 105 109 C for 2-3 h
Dispersion by chemicals 1 N NaOH/KOH at 25 C Dimethyl solfoxide at 25 C DMSO is a powerful H-bond acceptor, thereby breaking association H-bond in polysaccharide and in water. CH3Starch-OH ----- -O S+ CH3
Inclusion complex formationprecipitating the amylose as a complex with complexing agents (organic compounds) Starch + Complexing agent ComplexK = [complex] [starch] [complexing agent]K = complex formation constantKam >> Kamp
Aliphatic Alcohols; isopropyl, n-butyl, isoamyl, methyl
Lower aliphatic ketone
Lower aliphatic fatty acids
Benzenoid derivatives having aldehyde groups
FRACTIONATION OF AMYLOSE AND AMYLOPECTINSTARCH+DMSOBOILED, STIRRING ( UNDER N2)MIXTURE STORED 00 C CENTRIFUGATIONREDISSLOVED IN DMSOPRECIPITATE DISPERSE IN WATERREFLUX 3 hr.CENTRIFUGATIONPRECIPITATE SUSPEND IN 10% 1-butanolREFLUX 1h.ADD ETOHADD 1-butanol3-methyl-1-butanolwaterCool, keep overnight at RT.And 8 0C 24 hr.Supernatant 1 ( AP)Cool, keep overnight at RT.And 8 0C 24 hr.CENTRIFUGEPRECIPITATE DISPERSE IN WATERULTRACENTRIFUGATIONSUPERNATANT + WTER +1-butanolReflux 1h.Cool, keep overnight at RT. and 8 0C 24 hr.CENTRIFUGE PRECIPITATE DISPERSE IN 10% 1-butanol 1 literREFLUX 10 min.FILTERED THROUGH GLASS FILTER G-5REFLUX 10 min.Cool, keep overnight at RT. and 8 0C 24 hr.
*1RECRYTALLISATION**2 RECRYTALLISATION**3RECRYTALLISATIO*CHECK PURITY OF AMYLOSEGPC TOYOPEARL HW-75 F1 PEAKCENTRIFUGEGROUND WITH ETOHWASH WITH Diethyl EtherDRY IN VACUUM AT RT. OVER CaCl2AMYLOSESUPERNATANT 2 (AP )
Fractionation by retrogradation
A 7-9% slurry of potato starch is gelatinized at 85 C and homogenized in a blender. Sufficient energy is given the system to cause starch dissolution.
The mixture is then centrifuged and cooled so that the amylose separates in the form of globules from a liquid containing the amylopectin.
Fractional precipitation (salting out)industrially acceptable methodA commercial process salted out the amylose from potato starch with magnesium sulfate.
This method was based upon the fractional crystallization of amylose from a 10% by weight aqueous solution of potato starch in the presence of 10-13% magnesium sulfate.
In 1960, the Avebe Company in Holland produced 5.4 ton/day of amylose and 15.4 tons/day of amylopectin.
10% starch in 10-13% MgSO4 solution is solubilized by heating to 160 CCool down the solution (a phase separation occurs )The amylose separates in the form of small droplets and the amylopectin remains in the solutionBy cooling down to lower temperatures the droplets of amylose solution retrograde rapidly, forming small particles of amylose gel.Amylose gel is separated by centrifugation at 1000 g for 5 minWash out the salt by cold waterAMYLOSE
Amylopectin solutionTreat with more MgSO4 to precipitate all starch(including amylose remained)Ripen for 8 h at RT, the flocculent precipitate become insolubleWash the precipitate with waterAMYLOPECTINAmylopectin fraction is less pure than the amylose fraction