蔗糖酯對奈米/次微米纖維素懸浮液穩定性之研究

The effect of sugar ester on the stability of nano/submicro cellulose dispersion

陳時欣(Shih Hsin Chen)

指導教授 ： 葉安義

國立臺灣大學/生物資源暨農學院/食品科技研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.00952

摘要

纖維素是自然界存在量最豐富的多醣類，且可應用於食品和生物材料。不論是水溶性或非水溶性纖維素，對人類的健康都有很大的助益，諸如避免便秘甚至直腸癌、降低膽固醇、預防心血管疾病及減重等。本論文主旨在探討纖維素微粒於水相中之懸浮穩定性。實驗所採用之纖維素原料的體積平均徑為27.08 ± 14.00 mm，藉由介質研磨技術將其粒徑下降至奈米/次微米等級。以不同HLB值之蔗糖酯為乳化劑，穩定奈米/次微米纖維素懸浮液。探討蔗糖酯之HLB值、蔗糖酯之添加量及纖維素濃度對懸浮液穩定性的影響。濁度分析、粒徑分布及穿透式電子顯微鏡(TEM)則用於檢視纖維素懸浮液之穩定性。
2 g纖維素原料連同400 mL去離子水，以0.3 mm之釔鋯珠作為研磨介質，經過90分鐘研磨後，纖維素的平均粒徑會由數十微米大幅下降；最大粒徑為4 mm，且75 %的微粒為奈米/次微米等級，比表面積大幅提高。超細微粒懸浮液如未添加蔗糖酯作為懸浮穩定劑，會有相當明顯的聚集行為發生，呈現不穩定現象—濁度下降與粒徑增大均相當顯著。藉由適當蔗糖酯的添加則可促進纖維素懸浮液的穩定性。HLB值為3和7的蔗糖酯對於奈米/次微米纖維素於水相中的分散效果較佳，其建議添加量則分別為2.5 wt%和5 wt% (相對於纖維素之重量)。整體而言，濃度0.5 wt%的纖維素懸浮液無法以蔗糖酯的HLB值作為理想乳化劑選用的判斷標準。
研磨後纖維素懸浮液經離心(15000 ×g、60 min)後之上清液，其濁度及粒徑分布相當穩定；添加蔗糖酯之HLB值下降，穩定性隨之提高。經30天之室溫存放，添加HLB 3蔗糖酯之纖維素離心上清液，其濁度變化率低於1.3 %，添加HLB 7蔗糖酯者則低於3.1 %。離心上清液試樣中，懸浮的奈米級纖維素(< 100 nm)最高可達總懸浮微粒的60 %，懸浮液的總固形物濃度為650 ppm。固形物含量雖不高，但是總表面積卻是相當可觀，約7 m2/g，提高50倍以上。最後，穿透式電子顯微鏡則用於證實奈米微粒的影像。

關鍵字

奈米 ； 次微米 ； 纖維素 ； 懸浮液 ； 蔗糖酯

並列摘要

Cellulose is a naturally abundant polysaccharide, and has application in foods and biomaterials. Cellulose, water soluble or insoluble, has many benefits to human health, such as prevent constipation and possible colon cancer, reduce cholesterol under control, prevention of cardiovascular disease, and loss weight. In this article, the stability of nano/submicro cellulose particles dispersing in water is investigated. Raw cellulose with the volume mean diameter 27.08 ± 14.00 mm is reduced to nano/submicro scale by the processing of medium grinding technology. Sugar esters with different HLB values are applied to be the emulsifier to stabilize the dispersion of nano/submicro cellulose. The influences of the sugar esters with different HLB values and addition levels as well as the concentration effect of cellulose on the dispersibility of suspension are discussed. The turbidity, particle size distribution and TEM morphology are applied to examine the stability of suspension.
The volume mean diameter of cellulose is reduced from 27.08 mm to nano/submicro scale after medium grinding for 90 minutes, which the grinding medium is Y-Zr bead with average diameter 0.3 mm. Suspension without addition of sugar esters is unstable because of the significant aggregation of ultrafine particles, which results in the decrease of turbidity and the increase of particle size. However, the addition of appropriate sugar esters enhances the stability of the dispersion. Sugar esters with HLB 3 and 7 are in general performing good emulsifiers to stabilize the cellulose dispersion, and the suggested addition levels are 2.5 wt% and 5 wt%, respectively. The supernatant of cellulose dispersion after centrifugation (15000 ×g, 60 min) shows an excellent stability during the 30 days storage at room temperature, especially the sample with addition of HLB 3 sugar ester. The weight percentage of nano-particles in supernatant, which the total solid content is 650 ppm, is 60 %. Here, the specific surface area of the suspended particles in supernatant is 7 m2/g, 50 times higher than that of the raw material. Finally, the TEM photographs prove the morphology of nano/submicro cellulose.

並列關鍵字

nano ； submicro ； cellulose ； dispersion ； sugar ester

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