以靜電紡絲技術製作綠原酸抗菌保鮮膜

Abstract

保鮮膜是生活中常用於保存食品的材料之一，市面上常見的PE保鮮膜主要用於蔬菜水果等果蔬包裝，可抑制其呼吸作用、延緩老化。然而保鮮膜本身並不具有抗微生物能力，蔬果在生產、儲運等過程均可能接觸到食品病原菌，因此，藉由在保鮮膜上塗佈具有抗微生物能力的塗層，有助於抑制食品病原菌的生長，進而延長蔬果的儲存期限。綠原酸是一種天然抗氧化劑，常用於抑制癌症細胞增長、抑制發炎反應、抵抗病毒感染與降低血壓，也有文獻指出綠原酸具有抑制微生物活性之潛力，然而綠原酸雖具有良好的抗微生物活性，當其暴露於空氣與光時容易氧化；聚乙烯吡咯烷酮為一種高分子化合物，因毒性小而經常被應用於個人護理用品或作為食品添加劑；玉米醇溶蛋白具生物可降解性、容易取得與成本低廉等優勢，使其常作為保護與控制活性物質釋放的包覆載體。靜電紡絲是一種可高效率生產奈米纖維及高密度薄膜的技術，近年來逐漸普及於食品加工領域。本研究即以聚乙烯吡咯烷酮與玉米醇溶蛋白混合作為載體，利用靜電紡絲技術製作可抑制微生物生長之綠原酸薄膜。綠原酸薄膜之特性受諸多實驗條件的影響，包括溶液性質、操作參數與環境條件等，皆可能造成靜電紡絲製品的型態變化。結果顯示，以靜電紡絲技術製作之纖維在掃描式電子顯微鏡下呈現較扁平的緞帶狀且具有平滑表面，平均直徑介於273-590 nm之間；以高效液相層析儀分析並計算得知纖維對綠原酸之包覆效率介於72.5-90.7%之間，且包覆效率隨綠原酸濃度增加有上升的趨勢；此外，80 mg/ml綠原酸之樣品組別對大腸桿菌具有近100%的抑制能力。綜合上述之實驗結果，以靜電紡絲技術製作之綠原酸薄膜具潛力開發為輔助食品包材抑制微生物生長之材料。

When using food wraps for food preservation, microorganisms may still grow to the level that could cause pathological symptoms under improper storage environment. Thus, dispensing an antibacterial coating on the surface of the conventional food wrap could further inhibit the growth of typical food pathogens and extend the shelf-life of the contained food. Chlorogenic acid (CGA), a nature antioxidant, is commonly used for the prevention of inflammation, hypertension, cancer and viral infection. Many prevailing researches also indicated that chlorogenic acid has potent antibacterial activity, especially against food pathogens. Though chlorogenic acid shows good antibacterial activity, it is easily oxidized when exposing to air or light. Zein, a hydrophobic maize storage prolamine, is biodegradable and non-toxic for human. Therefore, zein is generally used as the base material for encapsulation vehicle for protection and controlled release of active compound. Polyvinylpyrrolidone (PVP) is a hydrophilic polymer excipient that is commonly used as the filament-forming matrix of electrospinning. In this work, zein and polyvinylpyrrolidone are selected as the carrier polymers for antibacterial film produced by electrospinning, which is an efficient technique for production of uniform polymer nanofibers and high-density film. The properties of chlorogenic acid nanofiber were optimized through adjusting the ratio of chlorogenic acid in the zein/PVP/ethanol solution, and processing parameters including pump flow rate, applied voltage and distance between needle and collector of the electrospinning system. In the final products, the average diameter of nanofibers with different CGA contents were around 273-590 nm with flat, ribbon-like surface when observed by scanning electron microscope. According to the images of transmission electron microscope, PVP presented as a well-protected carrier for the hydrophobic protein and the active compound. Moreover, 72.5-90.7% of chlorogenic acid could be encapsulated in the nanofiber films, which leads to improved antibacterial activity when compare to uncoated film. In addition, the coating made by electrospinning using this polymer solution may increase the water vapor transmission rate, which could reduce moisture residue and inhibit the growth of food pathogens such as Escherichia coli and Staphylococcus aureus. The result of antibacterial test showed that the electrospun fiber film can almost completely inhibit the growth of Escherichia coli. To sum up, electrospinning techniques serve as an efficient means to dispense potential antibacterial coating onto the surface of the food wrap. And this may help to improve the storability of food wrap and food packaging, further keep food pathogens away from food product.