The Research On The Technics Conditions And Characteristics Of Kiwi Dietary Fiber

The preparation, bleaching, physical and chemical properties of dietary fiber(DF) of Kiwi residue were studied in this paper. Enzymatic Method and Chemical Method were used to extract dietary fiber form Kiwi residue. The optimization of enzymatic preparing conditions for the DF from Kiwi residue was conducted by single factor and orthogonal tests. Results showed that the best conditions for purification evaluated by DF swelling ability were:(1) 1:20 (residue:0.4% of amylase),65℃, pH 6.0,80 min for amylase treatment; and (2) 1:20 (residue:0.4% of proteinase),50℃, pH 3.0,60 min for incubation. Finally,7.05 mlg-1 of swelling ability of DF was achieved. The optimization of chemical preparing conditions were:(1) 1:10 (residue:0.3% of NaOH),70℃,60 min for NaOH treatment; and (2) 40℃, pH 2.0,2 h for H2SO4, treatment. Finally,6.35 ml·g-1 of swelling ability of DF was achieved.Peroxide hydrogen was chosen as the bleaching agent. The optimization of bleaching conditions with microwave assistant decolored for the DF from Kiwi residue was conducted by single factor and orthogonal test. Result showed that the optimum bleaching conditions combination evaluated by DF whiteness was 4% of bleaching agent concentration, pH 10, bleaching time was 8 min and power was 800 W. Finally the whiteness could reach to 28.73 that was 19.43 higher than the value before bleaching. After bleaching the content of protein and starch reduced in the dietary fiber, whereas the content of DF was enhanced to 78.57%.The water holding capacity(WHC), oil holding capacity(OHC), water bonding capacity(WBC), swelling capacity(SC), and the adsorption capacity of NO2- of dietary fiber were improved after bleaching, but the adsorption capacity of heavy metal ion and sodium deoxycholate were falled. The result showed that the of kiwi dietary fiber before bleaching with the levels of WHC, OHC, WBC, SC at 5.24 g/g,1.06 g/g (rapeseed oil), 1.13 g/g(lard),4.31 g/g,7.05 ml/g, respectively, changed to 5.63 g/g,1.19 g/g (rapeseed oil),1.26 g/g(lard),4.53 g/g,7.67 ml/g after bleaching, respectively.The adsorptive ability of the kiwi dietary fibre for nitrite and bile sodium have been studied also in this paper. Under the condition of pH 2.0, the Kiwi dietary fiber had high adsorptive ability for nitrite with a maximum adsorptive rate of 0.139μmol/ (g·min), a minimum adsorptive concentration of 1.28μmol/L and the adsorptive equilibrium time of 72.6 min before bleaching. And after bleaching, they changed to 0.146μmol/(g·min), 1.17μmol/L,71.7 min, respectively. Its adsorptive ability for nitrite decreased sharply as pH increased. Under the condition of pH 6.0, the Kiwi dietary fibre had high adsorptive ability for bile sodium. Both its adsorptive ability and the time of adsorptive equilibrium increased sharply as the mass increased. When the masses of the Kiwi dietary fibres were 1.0,2.0,3.0,4.0 g, their final adsorptive rates were 24.5%,42.0%,64.5% and 86.0%, and the times of adsorptive equilibrium were 1.9,2.7,3.8,4.5 h, respectively. After bleaching, its final adsorptive rate was 11.5%,33.5%,57.5% and 82.0%, and the time of adsorptive equilibriumwas 2.1,2.9,4.1,5.0 h, respectively.Compared with raw matertias, the adsorptive ability of the enzymatic prepared Kiwi dietary fiber for Cd2+ and Pb2+ increased sharply, but they falled after bleaching. The maximum bound amount of Cd2+ for the dietary fiber before bleaching were 33.6μmol/g at pH 2.0 and 100.2μmol/g at pH 7.0, and it changed to 26.2μmol/g at pH 2.0 and 90.4μmol/g at pH 7.0 after bleaching. The maximum bound amount of Pb2+ for the dietary fiber before bleaching were 31.9μmol/g at pH 2.0 and 98.9μmol/g at pH 7.0, and it changed to 21.8μmol/g at pH 2.0 and 89.6μmol/g at pH 7.0 after bleaching. The minimum bound concentration of Cd2+ for the dietary fiber before bleaching were 83.3μmol/L at pH 2.0 and 17.5μmol/L at pH 7.0, and it changed to 125.3μmol/L at pH 2.0 and 21.3μmol/L at pH 7.0 after bleaching. The minimum bound concentration of Pb2+ for the dietary fiber before bleaching were 87.6μmol/L at pH 2.0 and 23.7μmol/L at pH 7.0, and it changed to 120.5μmol/L at pH 2.0 and 29.6μmol/L at pH 7.0 after bleaching.