介質研磨纖維素經噴霧乾燥後的形貌及包覆

Abstract

粒子因形貌與大小的不同，呈現不同的理化性質，也具有不同的功能性，噴霧乾燥技術可有效控制顆粒的型態，在溶媒蒸發過程中，讓液滴內的顆粒發生自組裝(聚集)，液滴內的顆粒大小是影響最終顆粒形貌的因子之一。藉由前人研究可知，5% (w/w)的纖維素經濕式介質研磨45分鐘，再經噴霧乾燥能形成似球狀顆粒，具有作為載體的潛力，因此本實驗進一步探討不同濕式介質研磨時間，所得到不同粒徑大小及分布的纖維素懸浮液，經噴霧乾燥後得到的粉末，分析纖維素粉末的物理性質及表面型態觀察，並以b-胡蘿蔔素作被包覆物質，評估其作為載體的潛力。 以5% (w/w)的纖維素，分別研磨15、30、45及90分鐘後，以進料溫度為130℃，進行噴霧乾燥。隨著介質研磨時間增加，纖維素的粒徑有遞減趨勢，必須將粒徑降至奈米/次微米等級才能發生聚集現象於噴霧乾燥過程中，粒子越小越容易發生聚集；研磨15分鐘經噴霧乾燥的纖維素外觀有縫隙，隨著研磨時間增加，小於1μm 粒徑的粒子數增加，外觀的縫隙減少，隨著粒徑之減小，表面趨於平滑，其表觀密度及表面積亦呈現遞減現象；進一步依孔隙度與密度的數據，得知內部結構緻密；包覆率方面，原材料為2.52%，顯示包覆能力不佳，研磨組研磨時間15、30、45及90分鐘的包覆量分別為19.38、23.57、26.36及21.19 %，皆顯著提升包覆的能力，以研磨45分鐘的條件最佳。

The change in particle morphology has resulted in variations of physicochemical properties and functions. Spray drying is a method to fabricate particles with a controllable size and morphology. During solvent evaporation, colloidal particles were self-assembled inside the droplet toward a close-packed array. With different particle sizes, which is one of the factors aggregating final particle morphology. In our laboratory, spherical cellulose particles have been prepared by utilizing media milling and spray drying. This study was to investigate the effect milling time on morphology and media-milled and spray dried cellulose, its encapsulation efficiency for b-carotene was also evaluated. 5% (w/w) microcrystalline cellulose was media milled for 15, 30, 45 and 90 minutes, and successively was spray dried at 130℃. The data showed that the particle size was decreased as the milling time increased. It appeared that, smaller particles particularly nano/submicron particle were prone to aggregate under the condition of nano/submicron scale particle size. Scanning electron micrograph, the spray dried cellulose powder from 15 min media-milled cellulose exhibited has highly rough surface. When the media milling time increased, the percentages of nano/submicron particles were increased. And the surface spray dried powder became smoother; with a decrease in apparent density and surface area. Data of porosity and density showed that the spray dried cellulose powders were dense particles. Obviously, raw cellulose would not the alike encapsulate b-carotene (encapsulation efficiency of 2.52%). The encapsulation efficiency of media-milled cellulose for 15, 30, 45 and 90 were 19.38, 23.57, 26.36 and 21.19%, respectively. It indicated that size reduction enhanced significantly the encapsulation behavior of cellulose. Among all the milling time tested, 45 min-milling was better choice for encapsulation.