經 Eudragit® 修飾泡沫細菌纖維素應用於食品活性包裝開發

Abstract

近年來，活性包材因能吸收或釋放功能性成分以抑菌、抗氧化而受到關注。細菌性纖維素 (bacterial cellulose, BC) 因兼具優良機械性與生物可降解性，使其具備成為環保活性包材之潛力，惟其高孔隙結構導致活性物質快速逸散，限制了 BC 之應用。本研究以泡沫系統製備高吸附性泡沫細菌纖維素 (foaming bacterial cellulose, FBC)，並以異位修飾方式將 Eudragit® (Eu) 與 FBC 結合形成具酸鹼響應溶解性的 Eu/FBC，再透過負載天然抗菌劑香芹酚 (carvacrol) 以開發兼具緩釋與抑菌功能之活性材料 Eu/Car/FBC。形態結果顯示，負載 Eu 與 carvacrol 不影響 FBC 外觀與完整性，且乾重與釋放量均呈 Eu 濃度依賴性，證明 Eu 可提升 carvacrol 之吸附與控制釋放能力。釋放實驗顯示，Eu/Car/FBC 在 pH 值為 6 和 7 之環境下，於 16 小時內快速釋放 carvacrol，而在 pH 值為 4 和 5 之環境可延緩釋放超過 72 小時，展現明顯的 pH 響應控釋特性。傅立葉轉換紅外光譜結果可於 990 cm−1 發現 carvacrol 特徵峰，證實 carvacrol 成功被負載進入 Eu/FBC;熱重分析顯示 carvacrol 修飾使 FBC 中溫區出現重量損失，而 Eu 的加入可進一步提升熱穩定性。掃描式電子顯微鏡觀察到 carvacrol 團聚於纖維表面;Eu 修飾則填補奈米纖維網絡，形成更緻密且連續之結構，推測有助於延緩釋放並提高活性成分穩定性。於抗氧化性測試中，Eu/Car/FBC 之 DPPH 與 ABTS 清除率分別達 0.09 與 2.7 mg TE/cm2。抗菌性評估結果亦顯示 Eu/Car/FBC 薄膜對 Escherichia coli 與 Staphylococcus aureus 具顯著抑菌能力，其抑菌圈直徑分別為 41.21 mm 與 49.55 mm，顯示其優異的廣效抗菌效果。應用於金目鱸魚片包裝時，Eu/Car/FBC 使總生菌數超過腐敗臨界值的時間延長 3 天以上;總揮發性鹽基態氮全程維持 15 mg/100 g 以下;脂質氧化指標亦顯著低於對照組。綜合而言，Eu/Car/FBC 展現優異的抑菌、抗氧化與緩釋性能，可望成為高風險魚類產品之創新活性包裝材料。

In recent years, active packaging materials have attracted increasing attention for their ability to absorb or release functional compounds to achieve antimicrobial and antioxidant effects. Bacterial cellulose (BC), which possesses excellent mechanical properties and biodegradability, has great potential to serve as an eco-friendly active packaging material. However, its highly porous structure leads to rapid loss of active substances, thereby limiting its applications. In this study, a highly adsorptive foaming bacterial cellulose (FBC) was prepared using a foaming system, and Eudragit® (Eu) was combined with FBC via ex situ modification to obtain Eu/FBC with pH-responsive solubility. The natural antimicrobial agent carvacrol was further loaded to develop Eu/Car/FBC, an active material with both sustained-release and antimicrobial functions. Morphological observations indicated that the incorporation of Eu and carvacrol did not affect the appearance or structural integrity of FBC. Both dry weight and release amount exhibited Eu concentration dependence, confirming that Eu enhanced the adsorption and sustained release of carvacrol. Release experiments revealed that Eu/Car/FBC rapidly released carvacrol within 16 hours at pH 6 and 7, while release was delayed for more than 72 hours at pH 4 and 5, demonstrating distinct pH-responsive sustained-release behavior. Fourier-transform infrared spectroscopy identified a characteristic peak of carvacrol at 990 cm⁻¹, confirming its successful incorporation into Eu/FBC. Thermogravimetric analysis showed that carvacrol loading led to weight loss in the medium temperature range, while the addition of Eu further improved thermal stability. Scanning electron microscopy revealed carvacrol aggregation on the fiber surface, whereas Eu modification filled the nanofiber network, forming a denser and more continuous structure, which was presumed to contribute to sustained release and enhanced stability of active components. In antioxidant activity testing, Eu/Car/FBC film exhibited excellent DPPH and ABTS radical scavenging capacities of 0.09 and 2.7 mg TE/cm², respectively. Antibacterial assessment further demonstrated that Eu/Car/FBC films had significant inhibitory effects against Escherichia coli and Staphylococcus aureus, with inhibition zone diameters of 41.21 mm and 49.55 mm, respectively, highlighting excellent broad-spectrum antibacterial activity. When applied to barramundi fillet packaging, Eu/Car/FBC extended the time for the total viable count to exceed the spoilage threshold by more than 3 days, maintained total volatile basic nitrogen below 15 mg/100 g throughout storage, and significantly reduce lipid oxidation compared with the control group. Overall, Eu/Car/FBC film exhibited excellent antimicrobial, antioxidant, and sustained-release properties, suggesting its strong potential as an innovative active packaging material for high-risk fish products.