Drying Method Of Young Pods,Large-scale Preparation And Properties Of Polysaccharide From Abelmoschus Esculentus(L.) Moench

Okra(Abelmoschus esculentus(L.)Moench),an annual herb of mallow,which contains pectin and polysaccharide,has many health functions and high value of development and utilization.Okra has been planted in many areas in China,with large output and high market value.However,as a fresh vegetable,the demand for fresh food is limited,the harvesting period is centralized,the fresh fruit is difficult to store,and it is easy to fibrosis,which leads to waste of resources.These have become the bottleneck of industrial development,such as the loss of nutrition and functional components caused by traditional drying technology,the lack of extraction and processing technology suitable for large-scale production of okra,the lack of new product development based on biological activity.In order to provide basis for high-value utilization of resources and industrial development,the drying method of okra pods,large-scale preparation of okra polysaccharide,physical and chemical properties and biological activities were systematically studied in this paper.The main contents and results are as follows:1.Drying method of okra pods.The effects of different pretreatment methods and drying methods on the drying rate and quality of okra pods were systematically studied with the vacuum pulse ultrasonic drying equipment(CN 104677066b)developed by ourselves.The drying time,total energy consumption and the content of polysaccharide and other functional components of okra were analyzed.The drying time and total energy consumption of ultrasound pulse with vacuum drying(UCVD)technology,which was developed independently by the experiment,were 53.33%and 21.80%shorter than vacuum freeze drying technology,and 2.78%and 56.64%shorter than hot air drying technology,respectively.The crude polysaccharide extraction rate of okra treated by UCVD was 17.34%,which was significantly higher than other samples.The dried product also retains the content of other bioactive substances and rehydration potential.UCVD effectively solves the problems of the loss of nutrients in traditional ultrasonic pretreatment,the transmission of solvent media and material pretreatment,and the supply of raw materials for subsequent polysaccharide extraction.2.Scale up test of preparation process of okra polysaccharide.The hot water stiring extraction technology of okra polysaccharide was studied.The optimum extraction conditions of okra polysaccharides were determined by single factor experiment and orthogonal experiment:the ratio of solid to liquid was 1:20,the extraction temperature was 85?,the extraction time was 2 h,the extraction was for 2 times.The average yield of okra polysaccharide was 16.78%and RSD was 1.16%in the repeated validation test.The properties of okra polysaccharide in laboratory scale-up,pilot plant scale-up and large-scale industrial scale scale-up were compared using the method and theory of process engineering.The yield of okra polysaccharide was slightly lower than that under the optimized conditions in the laboratory.The results of Rha/GalA ratio and infrared spectrum showed that okra polysaccharide was acid polysaccharide in different operation units,and had poly rhamnogalacturonic acid I(RG-?)structure.In the same scale-up stage of the project,the molecular weight of polysaccharide decreased with the operation sequence of hot water agitation extraction,vacuum concentration and vacuum drying unit.Compared with the changes of the properties of okra polysaccharide in laboratory scale-up experiment,pilot production and industrial production,the polydispersity coefficient of the pilot test and large-scale production shows that the molecular weight distribution of the two units of vacuum concentration and vacuum drying is wider,and the molecular structure may change.3.Preparation,properties and structure of okra polysaccharide.The separation and purification of okra polysaccharide were studied.The separation of okra polysaccharide by alcohol precipitation,high speed counter current chromatography(HSCCC)and membrane filtration were compared.Four components of okra polysaccharide(OMPE-1,OMPE-2,OMPE-3,OMPE-4)were separated by alcohol precipitation method.Their molecular weight(Mw)of OMPE-1,OMPE-2,OMPE-3,OMPE-4 were 2,277,2,970,59.63 and 3.10 kDa respectively.Three samples of okra polysaccharides(OMPH-1,OMPH-2,OMPH-3)were obtained by HSCCC.The Mw of OMPH-1,OMPH-2,OMPH-3 were 2.51,1.94 and 2,586 kDa respectively.The Mw of three samples(OMPMF,OMPUF OMPNF)separated by membrane filtration were 2,804,1.39 and 0.69 kDa.The polydispersity index(PDI)of OMPE-2,OMPMF,and OMPH-3 were 1.91,1.98 and 2.06,respectively.The molecular weight distribution of polysaccharides was similar.The monosaccharide composition of three samples(OMPE-2,OMPMF and OMPH-3)contained glucose,galactose,galacturonic acid,arabinose,glucuronic acid,mannose and rhamnose.The results of Rha/GallA ratio(71.36%,64.51%and 72.31%respectively)and infrared spectrum showed that they all had RG-? structure.The space microstructure of okra polysaccharide in solution was studied by AFM for the first time.The results showed that the okra polysaccharide was in irregular spherical arrangement and highly concentrated in high concentration solution,which made it have special high viscosity characteristics.4.Biological activity of okra polysaccharide.The biological activity of okra polysaccharide was evaluated from the aspects of antioxidant activity in vitro,antioxidant activity in simulated gastrointestinal fluid environment,hepatotoxicity test and animal experiment.The antioxidative activity of okra polysaccharide in vitro and the alleviation of physical fatigue were studied.The ABTS·+scavenging activity in order were OMPE-4>OMPMF>OMPE-2>OMPUF>OMPH-3>OMPE-3>OMPE-1 and the FRAP activities in the evaluation of antioxidant activity in vitro were OMPMF>OMPE-2>OMPUF>OMPE-4>OMPH-3>OMPE-3>OMPE-1 The polysaccharide component OMPMF and OMPE-2 have similar monosaccharide composition,all of which have galactose,galacturonic acid,glucuronic acid,mannose and rhamnose.The FRAP activity of okra polysaccharide decreased with time in the first 100 minutes.The results of 24-h toxicity experiments of L02 showed that when the concentration of okra polysaccharide was increased from 0.10 to 1.00 mg/mL,the survival rate of L02 cells remained at about 90%,even when the concentration was increased to 2.00 mg/mL,the survival rate of L02 cells also remained at over 80.00%,so okra polysaccharide had no significant toxicity to L02 cells(P>0.05).In the blood urine nitrogen test of mice,the water extract of okra has obvious function of relieving fatigue.The concentrations of blood urine nitrogen in the low,medium,and high doses of okra extract decreased by 18.26%,12.84%,and 13.56%respectively.In mice liver glycogen test,the contents of liver glycogen in different dose groups increased by 23.61%,2.89%and 11.56%respectively.In the blood lactic acid level test of mice before and after swimming,the removal rate of blood lactic acid in different doses were 64.64%,90.67% and 86.89% respectively.