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  • 學位論文

開發普魯藍抗菌活性包材用於延長冷凍鯛魚片 保存期限之研究

Development of a Pullulan Bioactive Packaging to Extend the Shelf Life of Frozen Tilapia Fillets

指導教授 : 鄭光成

摘要


普魯藍為真菌Aureobasidium pullulans所分泌的一種胞外多醣,其結構為麥芽三醣以α-1,6糖苷鍵鍵結而成,由於普魯藍的特殊結構,其展現出有別於其他多醣物質獨特的物理特性,例如黏著性、良好的成膜性、具有生物可分解性及外觀透明且良好的氧氣阻隔性等。因此,從普魯藍被發現以來便廣泛的應用於食品、醫療與化妝品工業上,像是血漿替代品、黏著劑、食品增稠劑、化妝品添加物等。但其極易溶於水的特性以及較高的生產成本限制了其應用性。 近年來由於環保意識的抬頭,加上地球暖化及能源危機的問題日漸嚴重,可分解性良好的生物性材料有逐漸取代由石油提煉的塑膠包材的趨勢,其中包括植物性與動物性的多醣,如澱粉、褐藻膠、幾丁聚醣等,以及微生物產生的多醣,如三仙膠、普魯藍等。微生物多醣以其安全、無毒及良好降解性等特性,已經被廣泛的研究與開發。其中,普魯藍具有較良好的成膜性且成膜後呈現透明無色,相較於其他多醣具有良好的氣體阻隔性。此外,普魯藍也是優秀的載體,在醫藥敷材上已經有許多攜帶活性物質的研究。因此,普魯藍具有開發成新穎且環保的活性食品包裝材料的潛力。 本研究利用普魯藍多醣製作成食品包裝材料,第一階段先評估三種交聯劑:戊二醛、硼酸與三偏磷酸對普魯藍水溶解性改善的效果,由於以三偏磷酸交聯後的普魯藍膜具有較好的抗水性及安全性,後續實驗選擇以三偏磷酸作為交聯劑。三偏磷酸交聯後的普魯藍外觀呈現吸水性良好的水膠狀,與以往的普魯藍薄膜不同。藉由FT-IR結果可發現O-H振動吸收波峰 (3300 cm-1)強度減弱,因此可間接證明三偏磷酸添加確實會使得普魯藍進行交聯反應。隨著提高交聯濃度雖能進一步提升耐水性,卻也抑制了普魯藍吸水的程度。此外,在提高交聯度的普魯藍會呈現出較強的機械強度的趨勢,但相較於未交聯的普魯藍膜的機械強度卻下降許多,較難應用於運輸型的第一層包裝材料,但良好的延展性與吸水性使其具有活性肉品吸水墊片的開發潛力。而後再將天然抗菌多肽乳酸鏈球菌素(Nisin),添加入普魯藍膜中,對大腸桿菌(Escherichia coli BCRC11634)、金黃色葡萄球菌(Staphylococcus aureus BCRC10451)、李斯特菌(Listeria innocua BCRC14843)、腸炎弧菌(Vibrio parahaemolyticus BCRC10806)等幾種台灣常見的食品病原菌做抗菌的測試,並發現在12小時內可將S. aureus與L. innocua至少下降2個對數值,大腸桿菌則是下降1個對數值。並將此活性普魯藍材料實際接觸於以接種病原菌的台灣冷凍鯛魚片,觀察其在15天之內的微生物生長情形及肉品腐敗情形,發現在10天之內可以有效減緩L. innocua與V. parahaemolyticus的生長速率,並在第10天觀察到分別下降2.11與1.66個對數值,此結果證明了普魯藍添加乳酸鏈球菌素活性墊片能有效抑制微生物的生長。期待未來普魯蘭可抗菌且環保的食品活性包裝系統,可以實際應用在食品上並有效降低食品中毒事件發生的機率且延長食品的保存期限。

並列摘要


Pullulan is an extracellular microbial polysaccharide produced from Aureobasidium pullulan. The basic unit of pullulan is maltotriose which is linked by α-1,6 glycosidic bond. Pullulan is highly water soluble but with low oxygen permeability, good film-forming, and adhesive properties. In addition, pullulan also exhibits good biocompatibility as well as great biodegradability. Because of those material properties mentioned above, pullalan has been applied in many fields such as denture adhesive, pharmaceutical coating, edible food coating and others. Since global warming and energy crisis are getting more and more attention, developing eco-friendly food package materials like polylactic acid (PLA) also arouse people’s interests. In this study, trisodium trimetaphosphate (STMP) was used as a crosslinking agent to improve the water resistance and physical properties of pullulan. In addition, nisin, a bacteriocin that produced by Lactococcus lactics, was incorporated into the pullulan film to develop an antibacterial food package system. The antibacterial activity of active pullulan film was also tested for common strains: E. coli, S. aureus, L. monocytogenes and V. parahaemolyticus. utilizing in vitro and on the meat. The water resistance was improved significantly since the weight loss could be reducing to 22% when concentration of STMP at 20 mg/ml, and the swelling degree was also increased to 73.16 g/g. The decreasing O-H stretching vibration(3300cm-1) of crosslinking pullulan in FT-IR spectra indicate a higher degree of crosslinking was formed with increasing concentration of crosslinking reagent. In the drug released test, bovine serum albumin releasing rate was higher in the 20 mg/ml STMP than other groups. In the antimicrobial activity test using dynamic shake flask test, nisin and EDTA incorporated pullulan hydrogel could at least reduce 1.12 and 2.72 Log cfu in the S. aureus and L. innocua. In the gram negative bacteria E. coli and V. parahaemolyticus, there were also 1.06 and 1.01 log inhibition in total cfu counting. In the frozen tilapia food package, frozen tilapia with active pullulan package could surely inhibit the growth of L. innocua and V. parahaemolyticus. In summary, the crosslinking strategy effectively improve the hydrophobic property of pullulan, and expect the active pullulan-nisin absorbend pad could apply to food package to extend the shelf life of meat.

參考文獻


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