Effect Of γ-Irradiated On Structure And Physicochemical Properties Of Konjac Glucomannan

Konjac glucomannan(KGM)is a water-soluble polysaccharides which polymerized by D-glucose(G)and D-mannose(M)with 1:1.5 or 1:1.6 throughβ(1→4)andβ(1→3)glycosidic bond.There is a branch chain in C-3 of M which is linked byμ-1,3 bond,and a acetyl group in every 19 glycosyl units(C-6).KGM has lots of unique charateristics such as the advantages of water boming capacity,gelling,thickening,adhesiveness,reversibility,suspension,film-forming ability, endowing flavor.Generally speaking,its molecular weight is 10~6 magnitude,in one side,the big masscan make it has good thickening and gel-forming properties,but in other side,its application ranges have been restrited greatly.So it is very significant that KGM was modified by chemical, physical and biological methods which can expand its application.Molecular degradation is an important research direction of KGM modification.The physical modification has the advantages such as simple operating,less pollution,for example,the microwave,UV,ultrahigh hydrostatic pressure and hydrothermal treatment,γ-irradiation was also considered as a physical modification of polysaccharide.It takes advantages of high perfomance and cheap.So it is very significant that KGM was degradated byγ-irradiation to expand its application.The paper adopted the KGMγ-irradiated at different dose(1～8kGy)and studied the effect ofγ-irradiationon on structure and physicochemical properties of KGM.The conclusions are as follows:(1)The effect ofγ-irradiation on structure of KGM were studied by ultraviolet(UV) Spectroscopy,Fourier transorm infrared(FT-IR)spectroscopy,X-ray diffraction,nuclear magnetic resonance(NMR).It showed that KGM underwent breakage of glycosidic bond on the long chain of molecules and viscosity average molecular decreased.But irradiated KGM is stillβ-pyranohexose and no new group was created.It caused the increase of the Carbonyl groups and decrease of the hydroxyl.The amorphous structure didn't change significantly but its peak value increases. D-spacing increases as the irradiation dose increased.(2)By determined the physical and chemical of indices on the irradiation KGM,it showed that the viscosity value of the non-irradiated KGM is 23000 mPa.s and the viscosity value was 12500mPa.s when theγ-irradiation dose was lkGy.So the viscosity value of.the KGM by γ-irradiation significantly reduced.By detecting the color value,it showed that brightness decreased, red and yellow increased.That because the browning teation.The reduction,sugar content of KGM increased firstly and then decreased.It was suggested that the irradiation treatment caused the rupturing of the glycoside bond and some goupes splitted out a few reduction sugar or create reductive polysaccharides.But during the irradiation browning reaction lead to consume a part of the reduction sugar and the reduction sugar content of KGM decreased significantly.(3)As the irradiation dose increased,the carbonyl groups were increaced and the hydroxyl was decreased too.As the resulte the carbonyl groups and hydroxyl related to the water solubility of KGM.It leaded the swelling degree ofγ-irradiated KGM to quickly decrease and the dissolution speed to become fast and binding capacity with the water to decrease.Besides,with storage time extened,the stability of the solution of KGM decreased.(4)After irradiation treatment,the KGM had good fluidity,excellent film-forming ability and easily taking the film.It was improved the softness and transparency of the KGM film.But its intensity was increased and its elongation was decreased.According to scan electron microscope, it showed that under the 500 multiple the surface of the non-irradiation KGM film had some protuberance or granular material.Under the 5000 multiple the film had kink mark and the film surface disoedered and loosed.Under the 500 and 5000 multiple,the irradiation of KGM had smooth surface,a little granular material,more and more ordereing and deriseing.It was observed that large granular contour after KGM was fully swelled.So it showed that the film-forming ability of KGM was improved.(5)It explained that the thermal stability gelling properties of KGM was significantly dscreased by the test of the thermal gel as the irradiation dose increased.Under 3kGy dose,KGM had the very weak gelling properties.But the springiness,adhesiveness,springiness,cohesiveness, gumminess,chewiness,resilience of gelation gradually decreased and its fracturability increased.By the test of the thermal gel,KGM with xanthosine formed complex gum and its hardness, fracturability,adhesiveness,gumminess,chewiness gradually increased and springiness,resilience gradually decreased,but its cohesiveness didn't obviously change.KGM with carrageenan formed complex gum and its hardness,springiness,cohesiveness,gumminess,chewiness,resilience gradually decreased and its fracturability gradually increased,but its adhesiveness decreased firstly and then increased,its clarity increaseed.(6)As played the solution of KGM for some times,it diseoveried that with the irradiation dose increased,mouldy KGM by the irradiation treatment was reduced.But through the bacteriostasis experimental,it showed that the irradiation treatment cann't reinforce the bacteriostasis properties of escherichia.coli,staphylococcus aureus,mucor,beer yeast.