胞外冰核蛋白及纖維素對過冷卻液體成核溫度之影響

細菌性冰核是目前發現的天然冰核物質中冰核活性最高者，但幾乎所有冰核細菌皆為植物致病菌或腸內桿菌，無法直接應用於食品中，本研究應用純化之胞外冰核蛋白，並以多層層積技術將冰核蛋白固定於PE膜上，希望能減少冰核蛋白對食品的直接接觸以及殘留，增加使用的便利性與可重複利用性，此外利用介質研磨提高纖維素的冰核活性，探討其取代冰核蛋白的可能性。應用固定有胞外冰核蛋白之PE膜於食品凍結時，可將原本於-8℃下不能凍結的純水和20%蔗糖溶液，於-8℃產生凍結，也可縮短鮮奶47.2%的總凍結時間，由原先的94.6分鐘下降至49.9分鐘。此固定有胞外冰核蛋白之PE膜也可減少魚肉肌動球蛋白受到冷凍傷害的程度，經過三循環的冷凍解凍後，Ca2+-ATPase活性由原本的38 %、21%以及19%提升至55 %、33%以及31%。添加纖維素於純水中，成核溫度由-21.7℃提升至-16.6℃，經過5分鐘研磨的纖維素，可將純水成核溫度提升至-13.0℃，隨著研磨時間增加，顆粒變小，但並未使成核溫度升高，反而導致下降，研磨90分鐘後，纖維素平均體積粒徑1.41 μm 的成核溫度為-16.1℃，故研磨5分鐘的纖維素具有較佳的冰核活性。實驗結果顯示，胞外冰核蛋白固定於PE膜後仍具有冰核活性，能減緩過冷卻現象、縮短總凍結時間以及維持冷凍食品品質，但此膜在使用的過程中，仍有胞外冰核蛋白滲入食品中的可能，於食用安全是個隱憂，因此纖維素具有取代冰核蛋白的可能性。

關鍵字

胞外冰核蛋白；纖維素；介質研磨；多層層積技術；能源節省

並列摘要

Ice nucleation active (INA) bacteria are known to be the most active ice nucleator (IN) found in nature to date. However, nearly all INA bacteria are plant-pathogenic or enterobacteriaceae, thus direct applications to food industry are limited. In this research, we utilize extracellular ice nucleator protein (ECIN) as an IN and immobilize it onto a polyethylene (PE) film by employing layer by layer deposition method to minimize direct contact with foods. In addition, we explore the possibility of media-milled cellulose as a replacer of ECIN. Coating ECIN on PE film resulted in freezing of 20% sucrose solution at -8℃, which does not freeze at normal conditions, and reduced 47.2% total freezing time of milk (from 94.6 min to 49.9 min). This film also can reduce the deterioration of fish actomyosin (AM) caused by freeze-thaw cycles during storage. The retention values for the three freeze-thaw cycles were greatly improved from 38%, 21%, 19% to 55%, 33%, 31%. The nucleation temperature of pure water was raised from -21.7℃ to -16.6℃ while cellulose was add. The addition of 5 min media-milled cellulose further raise the nucleation temperature to -13.0℃. Nevertheless, increasing milling did not further raise the nucleation temperature. For examples, 90 min milling resulted in smaller particle size (1.4 μm), but a nucleation temperature at -16.1℃. Our data show that ECIN can reduce the degree of supercooling, total freezing time and preserve the quality of AM even being immobilized onto PE film. Nevertheless, ECIN still have the possible to contact into foods. So, cellulose have the possibility as a replacer of ECIN.

並列關鍵字

Extracellular ice nucleation protein ； Cellulose ； Media milling ； Layer-by-layer deposition ； Energy saving

參考文獻

于達元。濃度對介質研磨纖維素流變性質的影響。國立台灣大學食品科技研究所

駱威達。卵磷脂與麥芽糊精對奈米/次微米纖維素懸浮液穩定性及其凍乾粉末覆

陳時欣。蔗糖酯奈米/次微米纖維素懸浮液穩定性之研究。國立台灣大學食品科

Arai, S.; Watanabe, M. Freeze texturing of food materials by ice-nucleation with the

bacterium Erwinia ananas. Agri. Bio. Chem. 1986, 50: 169-175.

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胞外冰核蛋白及纖維素對過冷卻液體成核溫度之影響

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