Preparation,Properties And Modification Of Dietary Fiber From Olive Pomace

Olive(Olea europaea L.)is a world famous species of subtropical oil trees,which is mainly planted in Gansu,Sichuan,Shanxi and Yunnan of China.Olive pomace are residues generated after the extraction of olive oil,with hemicellulose,cellulose and lignin as main components.They are a good source of dietary fiber.However the comprehensive utilization of olive pomace is very low.They are usually used as feed and fertilizer resulting in a waste of resources.Dietary fiber had many healthy physiological functions,such as weight control,improvement of the intestinal functions and cleaning of toxic substances etc.If the dietary fiber can be prepared from olive pomace,this type of dietary fibers with high bioactivity can improve comprehensive utilization value.In this thesis,the extraction,structural characterizations functional properties of soluble dietary fiber(SDF)and insoluble dietary fiber(IDF)from olive pomace was studied.The physical modifications of IDF using high pressure homogenization and colloid mill was investigated,too.The main contents and results were as follows:Using olive pomace as the raw material,the alkali method was adopted to extract soluble dietary fiber and insoluble dietary fiber,the physico-properties of SDF and IDF were researched.The extraction conditions of IDF and SDF were optimized through orthogonal test based on single factor test.The results showed that the optimum extraction conditions were concentration of NaOH 8%,the extraction temperature of 80 ℃,liquid-solid ratio of 15:1(mL:g),and the extraction time of 80 min.Under this condition,the yields of SDF and IDF were 28.74% and 52.39%,respectively.The water holding capacity,swelling capacity and oil holding capacity of IDF were 3.38 g/g,2.20 mL/g and 1.91 g/g,respectively.The water holding capacity,swelling capacity and oil holding capacity of SDF were 5.05 g/g,4.78 m L/g and 4.25 g/g,respectively.Glucose dialysis retardation index of SDF,IDF and defatted pomace were 13.22%、8.55% and 4.38% at the dialysis time of 90 min.While the results of scanningelectron microscope showed that IDF had looser morphology,more cavities and cracks,on the other hand,SDF had smaller particle size and more cavities after alkali extraction.The soluble dietary fiber(SDF)from Olive pomace was carried out using alkaline extraction method.The chemical composition and structural properties were characterized using chemical methods,i.e.,gas chromatography and infrared chromatography.Effect of olive pomace SDF on the in-vitro NO2-、Cd2+ adsorption and antioxidant activity was investigated.The results showed that the content of soluble dietary fiber in olive pomace SDF was 60.90%.The major component of monosaccharide of SDF from olive pomace was xylose,followed by the arabinose.Infrared spectra showed that SDF had the characteristics absorption peaks of polysaccharide.The adsorption capacity of SDF for NO2-in simulated gastric environment(98.92%)was greater than the simulated intestine environment(8.69%).The adsorption capacity of SDF for Cd2+ in simulated intestine environment(22.52%)was greater than the simulated gastric environment(3.78%).The maximum scavenging ratio of SDF for hydroxyl radical(·OH)was 46.34% at the mass concentration of 6 mg/mL.SDF had strong DPPH radical scavenging activity,and the IC50 of DPPH were 0.06 mg/mL.Olive pomace insoluble dietary fiber(IDF)was prepared by alkaline method with defatted olive pomace.In addition to its chemical composition and structure characterized by IR and X-ray diffraction,the effect of olive pomace IDF on the in-vitro adsorption capacity of NO2-、Pb2+、Cu2+、Cd2+ was studied,too.These results showed that the IDF content in olive pomace IDF reached 90.09%,which was mainly comprised by cellulose,hemicellulose and lignin.The result of IR showed that olive pomace IDF appears characteristics absorption peaks of sugars and lignin.The result of X-ray diffraction indicated that IDF had celluloseⅠcrystal structure,and its crystallinity achieved 47.94%.The quantities of equilibrated adsorption to NO2-using IDF under the simulated gastric condition(pH=2)was attained 826 μg/g at 240 min.The adsorption capacity of IDF for Pb2+、Cu2+、Cd2+ under the simulated intestine condition(pH=7)was far stronger than that in the simulated gastric condition(pH=2).The equilibrated adsorption quantities for Pb2+、Cu2+、Cd2+ in simulated intestine condition could reach 418.7,686.6 and 849.5 μg/g,respectively.Besides,the pseudo-second-order kinetics equations were exactly fit for those adsorption processes of IDF for Pb2+、Cu2+、Cd2+.Olive pomace IDF were physically modified by high pressure homogenization(HPH)and colloid mill(CM)in this thesis.The micromorphology,particle size distribution,functional groups,crystal structure and physico-chemical properties of IDF before and after the modification were analyzed.IDF by HPH had looser morphology,more cavities and cracks.The average particle size was 66.97 μm.IDF by CM had looser morphology and more fracture.The average particle size was 79.52 μm.HPH and CM modification didn’t affect IDF’s functional groups,crystal structure and crystallinity.IDF by HPH and IDF by CM showed the similar characteristics absorption peaks of sugars.They all had cellulose Ⅰcrystal structure.Compared with unmodified IDF,the water holding capacity,swelling capacity and oil holding capacity of IDF by HPH were increased by 31.70%,78.87% and 38.92%,respectively.The NO2-adsorption capacity and Cd2+,Pb2+,Cu2+ adsorption capacity of IDF by HPH were increased by 1.36%,6.97%,16.41% and 8.28%,respectively.The water holding capacity,swelling capacity and oil holding capacity of IDF by CM were increased by 19.93%,47.94%and 32.97%,respectively.The NO2-adsorption capacity and Cd2+,Pb2+,Cu2+ adsorption capacity of IDF by CM were increased by 8.20%,8.95%,13.71% and 6.36%,respectively.