Study Of Squeeze Dewatering And Its Resource-Oriented Utilization Technology Of Banana Pseudostem

China is the second largest producer of bananas in the world.Every year after the harvest of banana,a large number of by-products,the banana pseudostem,increase sharply.The banana pseudostem processing is difficult and utilization rate is low due to the bulkiness of the banana pseudostem,high moisture content and strong intensity of labors which brings increasingly serious environmental pollution problems.Based on the concept of agricultural waste resource utilization and environmental protection,the banana pseudostem at present as a lot of waste discarded as a renewable resource was used.A lot of researches focus on the corn straw at home and abroad,but the utilization of banana pseudostem is rare,especially the banana pseudostem has many characteristics different from corn straw,so this paper aimed at the problems existed in the utilization of banana pseudostem.Firstly the quality of banana pseudostem is large,not only the yield of banana pseudostem is large,but also the banana pseudostem itself with high water content,larger volume,so this paper mainly was focused on the researches of squeeze dewatering processes and mechanism of banana psedostem.Secondly the higher colloid content of banana pseudostem,so the problem of fibers degumming process by chemical,emzyme and mechanical methods were studied.Moreover this paper also studied the process of extracting the tannic acid which was a special ingredient from banana pseudostem.Although a lot of researches fouced on the extracting process of fibers,the extraction of banana psedostem tannic acid and its antioxidant properties were studied in this paper,it is in order to seek a high added value of the utilization of banana pseudsotem.The main work and conclusions are as follows:(1)The morphology of banana pseudostem and fibers,chemical component and thermogravimetric characteristics of fresh banana pseudostem were studied firstly.The content of moisture and protein,ash and chemical composition were measured.The protein content was also measured.The thermal properties of fresh banana pseudostem raw materials of different layers in different parts were analyzed.The results showed that water content of the banana pseudostem was up to 92%;Ash content was 13.12%;Protein content was 8.79%.The banana pseudostem(dry basis)was composed primarily of cellulose(21.77%),hemicellulose(25.92%),wood grain(10.88%)and pectin(3.50%),waxy fat(3.63%)and water soluble matter(31.91%).It can be seen that the content of non cellulose was higher than the content of cellulose.(2)The technology and mechanism of squeeze dewatering were studied.The experiments of hydraulic expression and roller expression were conducted by using plate curing machine and crepe machine respectively.The results indicated that the dewatering rate showed linear growth with the increasing of hydraulic pressure when the hydraulic pressure and the diameter within a certain range.In the experiment of retention time,the dewatering rate was increased at first and then decreased and approached at a constant value with prolonging the retention time.In the roller expression experiments,when the thickness of feed material in a constant,the dewatering rate was linearly decreased with the increasing of roller clearance.The relative clearance was introduced in this paper.With the increasing of the relative clearance,the dewatering rate had gradually growth pattern.The mechanical model between pressure and roller clearance was established by the theory of non-classical contact mechanics of K.L.Johnson.The model equation between roller clearance and dewatering rate was established in this paper based on the research of the theory of roller expression of banana pseudostem.Moveover the sap flow model of roller expression was discussed.(3)The characteristics and applicability between hydraulic expression and roller expression was contrasted comprehensive.The roller expression was chosen as the expression form in the automatically adjustable roller press.Based on the research above,the automatically adjustable roller press was designed and manufacture independently.The machine can adjust the roller clearance automatically according to the diameter of the raw materials.The dewatering rate was reached 50.2% by the experiments of pressing whole stem by automatically adjustable roller press.(4)Since there was no mature technology for degumming to extract banana pseudostem fiber,in this paper,the degumming processes by chemical method,ultrasonic-semicellulase-pectinase method,protease-pectinase method,mechanical method were researched.The fibers by those methods under optimized conditions were obtained.And considering the aspects of environment,process and the refined degree of fiber,the protease-pectinase method has a good prospect of application and development through analysizing of he advantages and disadvantages of those fibers.(5)The structure and performance of fibers by chemical method,ultrasonic-semicellulase-pectinase method,protease-pectinase method,and mechanical method were systematically studied.Then relationship between the composition and mechanical property of fiber was researched.According to the theory of fiber reinforced composite,the degradation of hemicellulose was the main cause for the decrease of tensile strength of fibers by ultrasonic-semicellulase-pectinase method.(6)In this paper,using the dehydrated banana pseudostem as as raw material,an extraction and purification process was developed to get a banana peseudostem tannic acid.And the purified products were measured and characterized to evaluate its antioxidant activity.With best conditions,the extraction yield of tannic acid was2.82%,the purity was 48.54%.FTIR results showed that the extraction product contained polyhydroxy phenolic esters.GPC results showed that banana stem tannic acid with molecular weight between 3.43 × 104 and 4.43 × 104.The free radical scavenging rate was 86.59% by DPPH method,when the concentration reached 0.6mg/mL.Research results of this thesis provided theoretical basis for the dewatering of banana pseudostem,extraction and application of fiber degumming and a model which may be useful for comprehensive utilization of banana pseudostem in industry was established.There was a certain theoretical significance and application value for dehydration,banana pseudostem degumming extraction of the whole pseudostem of banana.