Study On The Physical Modification Of Dietary Fiber In Garlic Skin And Inhibition Of Lead Adsorption

Dietary fiber(DF) was regarded as the seventh nutrients. Dietary fiber,especially soluble dietary fiber(SDF), exhibit irreplaceable physiological functions.However, low level of SDF in natural materials severely limits its application in industry. Garlic skin, a by-product in garlic products industry, contains 70% of dietary fiber while SDF only makes up 5%.The purpose of this paper was selecting modification technology for garlic skin so as to improve the proportions of soluble dietary fiber. Then through animal experiments, the study of garlic skin dietary fiber on heavy metals adsorption in rats was investigated. Nevertheless this work has important theoretical significance and practical value. The main creative conclusions drawn by the research are as following:(1) Twin-screw extrusion, steam explosion and high temperature cooking was investigated respectively to modify garlic skin. To further promote the soluble dietary fiber, the cellulose enzyme was employed after physical treatment. The results showed that the SDF content was improved significantly by physical treatment which was up to 15.87%, 15.04% and 10.54% respectively. While SDF level only further improved with cellulose enzyme by 0.97%, 0.95% and 1.06%.Hence direct physical modification can meet the needs of the physiological function enhance of garlic skin dietary fiber. Twin-screw extrusion and steam explosion are both effective in improving SDF level. In addition, another twelve basic component tests were researched. Compared with steam explosion or high temperature cooking, twin-screw extrusion not only improved 199% in SDF, but also increased total sugar and soluble polysaccharides by 98% and 429%respectively. SDF accounted for 26%of total dietary fiber(TDF).Therefore twin-screw extrusion is relatively a better modification technology.(2) The microstructures and physical-chemical features of treated and untreated SDF were explored with the aid of scanning electron microscope(SEM) and atomic force microscope(AFM), FT-IR, simultaneous thermal analyzer and colorimeter.The results showed that the physical treatment changed surface structure greatly and increased surface roughness. Especially for twin-screw extrusion, The honeycombstructure on the surface and small particle size greatly increased the surface area of extrusion-treated SDF. The infrared spectrum showed that the uronic acid content in extrusion SDF increased greatly. All of these changes may increase the binding capacities with metal ions. Compared with untreated SDF, the treated SDF showed better thermal stability. The color measurement results showed that physical treatment significantly changed the color of SDF, and the steam cooking changed most while extrusion changed least. Accordingly the results above further proved that twin-screw extrusion is better in garlic dietary fiber modification.(3) The study of garlic skin dietary fiber modified by twin-screw extrusion on the lead adsorption and distribution in rat was conducted. DF increased lead excretion in urine and feces and decreased the lead adsorption with addition of20mg/kg, 100mg/kg or 200mg/kg in diet. But increasing DF amount did not mean more decrease in lead adsorption. DF changed the lead distribution in rat tissue.With lead addition of 100 mg/kg in diet, DF of 5% in diet decreased the lead accumulation in kidney and in femur. However with lead addition of 200 mg/kg in diet, DF of 5% in diet increased the lead accumulation in liver, kidney and in femur.