研磨對臭氧降解纖維素的影響

Abstract

纖維素為自然界中存在量最多的碳水化合物，在生物材料及食品的應用上都具有相當的潛力。經生物或化學方法降解，產生的水溶性纖維素與寡醣，為可溶性膳食纖維，具有對人體有益的生理活性，例如預防腸道疾病和降低血中膽固醇等。纖維素經過機械研磨後，平均粒徑下降，表面積提高，應能促進各項反應的進行。本研究探討機械研磨對臭氧降解的影響，不可溶性纖維素、體積平均粒徑為指標，了解纖維素變化的情形；以pH值作為酸性副產物生成的指標。經研磨後纖維素以不同臭氧劑量處理，期望能找到纖維寡醣產量高，副產物產量低的反應條件。 纖維素經研磨0、20、60、100分鐘後，體積平均粒徑分別為27.08μm、10.58μm、5.558 μm、3.562 μm，以臭氧(濃度43 mg/min、86 mg/min)進行反應。結果顯示，研磨時間愈長，不可溶纖維素含量下降愈快，高臭氧濃度使水解率增快。通常研磨纖維素，應促使其與臭氧反應時，葡萄糖和纖維寡醣產量的產生，但100分鐘的研磨，寡醣產量比60分鐘低。研磨後，低臭氧濃度之反應，有助於葡萄糖和纖維寡醣生成，研磨60分鐘的生成量最高。臭氧降纖維素時，pH值會下降，顯示酸性物質的產生，研磨和臭氧濃度皆會影響纖維素水解液之pH值變化，一但經過研磨，於臭氧反應時，pH值下降幅度較大，臭氧濃度愈高，pH值下降幅度愈大。在反應的過程中也發現二氧化碳的產生，可能是酸性物質再氧化所致。纖維素在臭氧降解的過程，體積平均粒徑隨反應時間而下降，高臭氧濃度使其下降速率加快，且發現1 μm以下的粒子逐漸增加，結果顯示，結合研磨與臭氧，可製備小於1 μm的纖維微粒。

Cellulose is the most abundant carbohydrate on the earth, and it is potential application in food and biomaterial field. The water soluble cellulose and oligomers are the hydrolyzed from cellulose, via biological and chemical methods, have been reported to be beneficial to human body. Milling cellulose reduced the particle size and thus increased the surface area, which would enhance chemical reactions. This was to investigate the effect of mechanical milling on ozonolysis of cellulose. Insoluble fractions and volume mean diameter were used as indexes for the change of cellulose. The pH value was employed as an index for the formation of acidic compound. The purpose of this study was to search a process combing milling and ozonlysis for producing cello-oligomers. After being milled for 0, 20, 60 and 100 min, volume mean diameter of cellulose were 27.08, 10.58, 5.558 and 3.562 μm, respectively. The particle size was further reduced by ozonolysis. Generally, milling resulted in the formation of glucose and cello-oligomers. However, 100min-milling yield cello-oligomers less than 60 min-milling. In addition to reduce the particle size, ozonolysis induced the formation of cello-oligomers. In this study, the 60 min-milling with low dosage of ozone yielded the most oligomers. Both milling and ozone dosage affected the change in pH value. High dosage of ozone resulted in more pH dropped. Probably due to the further oxidation of acidic compounds, CO2 was fund in the eluting gas. During the ozonolysis, the particles smaller than 1μm was increased, the results indicated that it was feasible to prepare cellulose nanoparticle by milling and ozonolysis.