Research On Extraction Technology Of Pomelo Peel Dietary Fiber And Its Functional Characteristics

This dissertation, taking pomelo peel as raw material, conducts a research on the best process to extract pomelo peel pectin and insoluble dietary fiber (IDF) and then to study the physicochemical property of the pectin and fiber through chemical analysis method and instrumental analysis techniques. Finally, by establishing animal experimental model, it makes a study on the physiological function characteristics of pomelo peel pectin, pomelo peel insoluble dietary fiber (PPIDF) and pomelo peel (PP), which provides the theory basis for utilization of pomelo peel dietary fiber (PPDF) in the food industry. The main conclusions of the research are as follows:1. The best extraction technology of pomelo peel dietary fiber research conclusion is as follows:(1) This dissertation takes acid-hydrolysis and alcohol precipitation to extract pomelo peel pectin. On the basis of single-factor experiment, and by means of studying the influence of different extraction temperature (℃), extraction pH, extraction time (min) and solid-liquid ratio (mL/g) on yield of pomelo peel pectin through orthogonal experiment, it comes to a conclusion that the best condition to extract pomelo peel pectin is in the temperature of100℃,pH value2,60min and the best solid-liquid ratio is50mL/g. Under the condition, the yield of pomelo peel pectin is26.16%.(2) This dissertation chooses sequential treatment with sulfuric acid followed by sodium hydroxide to extract insoluble dietary fiber (IDF) in pomelo peel. Based on single-factor experiment, it discusses how NaOH concentration, NaOH treating temperature, treating time and HC1treating temperature affect the yield of pomelo peel insoluble dietary fiber (PPIDF) by way of orthogonal experiment. The experiment shows that the best extraction condition of PPIDF is, NaOH concentration2%, NaOH treating temperature30℃, NaOH treating time50min, HC1treating temperature90℃. The composite score of PPIDF got in this condition is61.13%.2. Determination of physical and chemical properties of pomelo peel dietary fiber conclusion is as follows:(1) The research on the physicochemical property of pomelo peel pectin shows that the purity of pomelo peel pectin is84.3%, the esterification degree of which is73.75%. Normally, the pH value of pomelo peel pectin stays at4.86, shown as acidity high-fat pectin, which meets the standard of commercial pectin. The thermal stability of pomelo peel manifests its viscosity drops rapidly along with the time and tends to be stable after15min. The solubility of pomelo peel pectin is affected by temperature and the pH value of solution. As the temperature goes up, the solubility goes down; and with the pH value goes up, the solubility tends to go down. The viscosity of pomelo peel pectin closely relates to the concentration and temperature of pectin, the pH value of solution, the concentration of sucrose and so on. Its viscosity goes up with the increase of pectin concentration, decreases when pH value and temperature goes up and rises along with the increase of the concentration of sucrose.(2) According to the study on the physicochemical property of pomelo peel insoluble dietary fiber (PPIDF), its purity is87.7%, expansibility7.92mL/g, water-holding capacity13.38g/g, the ability to adsorb unsaturated fat (soybean oil)8.62g/g, the ability to adsorb saturated fat (lard oil)11.26g/g, the ability to adsorb copper ion32.5mg/g, the ability to adsorb lead ion54.8mg/g, which all enhance at different levels in comparison with pomelo peel raw material.3. The dissertation picks30SD adult female rats and randomLy divides them by weight into5groups. Before that, those rats are fed with basic forage for a week. Then four of the five groups are double ovariectomized and one week later assigned as model control group (OVX-CN), pomelo peel raw materials group, pomelo peel pectin group and pomelo peel insoluble dietary fiber group (PPIDF). The rats in the fifth group are sham-ovariectomized as sham control (sham-CN). After four weeks, all five groups are dissected and the results shows as follows:(1) Compared with group sham-CN, group OVX-CN increases weight and the forage availability (P<0.05) apparently, besides, blood lipid, liver total fat, total cholesterol and triglyceride total content of the rats in this group all tend to increase, which, indicates that this experiment successfully makes a model to simulate climacteric animal.(2) In comparison with group OVX-CN, rats in group pomelo peel raw materials, group pomelo peel pectin and group PPIDF all tends to decrease in respects of weight, forage availability, blood lipid, liver total fat, total cholesterol and triglyceride total content. Among them, group pomelo peel pectin shows the most obvious decline (P<0.05).(3) To add pomelo peel raw materials, pomelo peel pectin and insoluble dietary fiber (IDF) from pomelo peel (P<0.05) in forage can drastically increase the concentration of short-chain fatty acids, defecation, cecum content and the area of cecum in the rats, decrease the pH and free ammonia of cecum contents, and increase the amount of beneficial bacteria and inhibite harmful bacteria growth in intestinal environment, thus improve the intestinal environment.