The Study On Preparation Process Of Dietary Fiber And Microcrystalline Cellulose From Asparagus Stems

Asparagus stems are the remains of asparagus after harvest,and they are mainly processed into fodder or burned directly at present.A large number of nutrients such as saponins and dietary fiber in the asparagus stems can not be fully utilized.This paper determined the components of asparagus stems and studied the optimum preparation process of dietary fiber and microcrystalline cellulose from asparagus stems.In addition,the method of preparing by-product into nutrient solution was discussed from the point of view of economic and nutritional value.The results are as follows:?1?This paper determined the content of the basic compositions of asparagus stems such as moisture,ash,protein,dietary fiber,starch,fat and the content of active ingredients such as saponin,rutin,resveratrol,quercetin and selenium and so on.The results were that water in stems was 8.20?1.07%,protein was 5.17?1.42%,ash was2.54?0.93%,starch was 5.95?1.71%,fat was 3.03?0.76%,and total dietary fiber was 76.41?3.02%,of which soluble dietary fiber was 2.01?0.87%and insoluble dietary fiber was 71.84?2.29%;the content of saponins,quercetin,rutin,selenium and resveratrol was 2.13?0.41 g/100g,1.17?0.02 mg/100g,24.85?0.10 mg/100g,58.60?2.18 ng/100g and 2.56?0.03 mg/100g,respectively.?2?Orthogonal test was used to optimize the enzymatic extraction condition of IDF.The results indicated that the enzyme concentration of thermostable alpha amylase,glucoamylase and acid protease was 1.25%,0.90%and 1.10%,respectively;the enzymolysis temperature was 75?,55?and 45?,respectively;pH was 6.5,4.5and 3.5,respectively;enzymolysis time was 100 min,120 min and 80 min,respectively.?3?The optimum conditions for decolorizing the by-product of the activated carbon based on the decolorization rate and the retention rate of saponin were:under the condition of pH=4.5,1.5%?m/v?activated carbon was added and decolorized for 45min at 50?.?4?The composition and physicochemical properties of IDF product which was extracted by enzymatic method were determined.The results showed that the purity of IDF reached 80.03?2.42%,water holding capacity was 9.84?2.17g/g,swelling was4.09?0.94mL/g,and oil holding capacity was 4.67?1.35 g/g.The adsorption capacity of NO₂^-and cholesterol at pH=7 was 1.31?mol/g and 7.73 mg/g while the adsorption capacity was 15.75?mol/g and 3.32 mg/g at pH=2.In addition,this kind of IDF had a good ability of cation exchanging capacity.?5?The optimum conditions of hydrogen peroxide bleaching obtained by orthogonal test were:bleaching at 55?for 90 min with 7%H₂O₂ charge and 0.7%NaOH charge.The process parameters of the preparation of microcrystalline cellulose through dilute acid degradation method were optimized by response surface test.The optimization results were that the hydrolysis temperature was 95?,the mass fraction of hydrochloric acid was 6%,and the ratio of material to liquid was 1:20?m/v?.The yield was 43.57%under this condition for 60 min.?6?Microcrystalline cellulose prepared from asparagus stems was transparent rodlike material and less than 100?m in size.The average degree of polymerization of91.97 was prepared by acid hydrolysis,and carbohydrate content reached 101.53%.The results of infrared spectroscopy and XRD indicated that the index of asparagus stems microcrystalline cellulose crystallinity was 61.42%,retaining the structure of natural cellulose in materials.