Study On Preparation And Properties Of Pea Resistant Starches

In this study, pea starch was used as raw material, and subjected to enzymaticdebranching, heat-moisture treatment, cross-linking and cross-linking combined withheat-moisture treatment to obtain a resistant starch-rich powder with functional characteristics.Furthermore, the morphology, thermal property, crystallinity, viscosity and digestion ofresistant starch were characterized by polarizing microscope, SEM, DSC, XRD, Viscographand In vitro digestion techniques, respectively.Resistant starch was prepared by enzymatic debranching. The samples were cooled downand stored for12h after debranching treatment using300ASPU/g pullulanase for12h, theyield of RS reached52.66%. The granular structure of the resultant pea starch was completelydestroyed. The solubility and swelling power of samples decreased with the increase of RS.The native C-type starch was converted into typical B+V type pattern. The relativecrystallinity of samples increased initially, then decreased. Gelatinization temperatures andenthalpy of gelatinization of RS products increased compared to native starch. The viscosityof RS samples declined dramatically. And viscosity of highly debranched samples dropped toaround zero. Moreover, the breakdown and setback values of all samples decreased comparedwith native starch. The In vitro digestion result indicated that the amount of digested productsdecreased with the increase of RS.Pea starch was subjected to heat-moisture treatments (HMT) to evaluate the influence ofmoisture content, treated temperature and time on RS formation. The result indicated that RScontent reached the peak at26.36%when the starch treated with the moisture content of35%at130℃for12h. Scanning electron microscopy (SEM) showed that the starch granulestructure did not substantially change, but some pores or cracks were detected. The polarizedlight microscopy of RS suggested that the apparent intensity of birefringence was lower thannative starch. The native C-type starch was converted into type A. The relative crystallinity ofsamples increased by5.26%-16.16%. The solubility and swelling power of samples increasedwith the increase of reaction temperature. And the swelling power rose at first, then droppedgradually with the increase of RS content. Gelatinization temperatures increased but enthalpyof gelatinization decreased in HMT starches. Using garden pea starch as the raw material, cross-linking technique was applied toobtain resistant starch. The experimental factors include the usage of cross-linking, reactiontime and temperature were investigated. The highest RS content (63.63%) was reached whenthe starch treated with12%at45℃for4h. When12%of cross-linking agent was used,products containing0.38%of phosphorus could be obtained by optimizingcross-linking pH, retraction temperature and time. The polarized light microscopy of RSsuggested that the apparent intensity of birefringence was lower than that of native starch. Thesolubility and swelling power of RS samples declined significantly with the increase of RS.Both the native and resistant starches showed C-type X-ray diffraction pattern. Relativecrystallinity increased after modification. The viscosity of RS samples declined dramatically.And viscosity of highly cross-linked samples dropped to around zero. The gelatinizationtemperatures of cross-linked starch increased, while enthalpy of gelatinization decreasedslightly compared to native starch. The FTIR spectra of cross-linked starch showed that theabsorption peak at3456cm^-1disappeared, the absorption band at2948cm^-1enhanced, whilethe absorption band at1392cm^-1declined.Cross-linking combined with heat-moisture treatment of garden pea starch was carried outfor obtaining resistant starch. In the optimum reaction condition, the achieved highest RScontent was68.96%. Scanning electron microscopy (SEM) showed that the starch granulestructure was disrupted, some starch granules adhered and piled up together, and there weresome pores or cracks exist. The gelatinization temperatures of RS samples increased, whileenthalpy of gelatinization decreased slightly compared to native starch. The X-ray diffractionpattern of resistant starches still exhibited C-type. However, there were some differences thatmight indicate the presence of A-type crystals. And Relative crystallinity increased aftermodification. Furthermore, the advantages and disadvantages of the four methods werestudied. The four techniques mentioned above were turned out to be effective in preparingresistant starch and different aspects of garden pea starch were affected to some extent aftermodification process.