Studies On Preparation And Properties Of Cassave Resistant Starch

In this study, the cassava starch was used as raw material. The cassave resistant starchdetermination method was studied firstly. To improve the content of resistant starch, theautoclaving method and autoclaving assisted enzyme treatment were used to prepare cassaveresisitant starch and the parameters were also optimized with response surface methodology.At the same tine, the cassave resistant starch was prepared by cassave. Finally, the propertiesof cassave starch and cassave resistant starch were studied.The best cassave resistant starch determination method was AOAC-GOPOD. Theoptimized conditions of preparing resistant starch by autoclaving method were that10.1%ofstarch slurry concentration was autoclaved for79min at121℃, and then incubated for24h at4℃. With this method, the resistant starch content is5.25%. The optimized conditions ofpreparing resistant starch by autoclaving assisted enzyme treatment were that when10.1%ofstarch slurry concentration was autoclaved for79min at121℃, added1NU α-amylase pergram of starch to react15.75min at95℃, debranched with0.83NPUN pullulanase per gramof starch at55℃for5.86h, then treated with ultrasonic for2min, finally retrograded at4℃for24h to improve resistant starch formation, the content of resistant starch increased to15.27%. Compared with autoclaving method, the content of resistant starch was enhanced by3times with autoclaving assisted enzyme treatment.The conditions of starch extraction were also discussed. The results was that under theratio of liquid to solid8:1, temperature30℃and time3h, the starch content was80.57%. Inthe cassave starch, the content of protein, lipid and ash were very low, almost closing to zero.The content of the cassave resistant starch which was used cassave and prepared byautoclaving assisted enzyme treatment was14.67%and close to15.27%. So this method ispossible.Compared with raw starch, the granule appearance of resistant starch changed irregularunder scanning electron microscopy. Amylose content of RS samples increased, but notproportional to the content of resistant starch. X-ray diffraction showed that the cassava starchhad A type pattern with sharp peaks at15°,17°,18°and23°. The resistant starch prepared byautoclaving method did not have sharp peaks and the crystallinity was close to zero. Theresistant starch prepared by autoclaving assisted enzyme treatment had B type pattern withsharp peaks at17°and22°and the crystallinity of resistant starch improved with increasingresistant starch content. The viscosity of RS decreased and the trough viscosity of RS which prepared by enzyme treatment was close to zero. The digestibility of starch was studied by invitro method. The results indicated that the total digestion products and the digestion rateswere both decreased with increasing resistant starch content, but the total digestion productswere increased with increasing reaction time. The solubility and swelling capacity increasedwith increasing reaction temperature. The swelling capacity of RS decreased compared withcassave starch. The solubility of RS prepared by autoclaving method was decreaed, but thesolubility of RS prepared by enzyme treatment was increased. The transparency of RS wasalso decreased.