重組抗凍蛋白及聚麩胺酸於香蕉貯藏及冷凍 加工之應用研究

Abstract

抗凍蛋白(antifreeze protein;AFP)為某些生存於寒冷區域生物體內特有之蛋白質，具有修飾冰晶構形，降低生物體體液凍結點之功效。本實驗使用之抗凍蛋白為本實驗室利用人工合成方式，將魚類之第一型抗凍蛋白類似物基因於Bacillus subtilis表現重組抗凍蛋白(rAFP)。並已通過美國FDA食品級浸漬物核可。 聚麩胺酸(poly-γ-glutamic acid;γ-PGA)具有增稠、乳化、凝膠、成膜、抗凍、吸附、保濕、黏接、生物可分解性、溶解血栓等特性。已應用於食品、健康保健食品、醫學、化妝品、環境保護、畜產及農業等領域。本實驗所使用之聚麩胺酸為本實驗室所構築之Bacillus subtilis PGA 6-2轉形株所生產，本研究探討rAFP及γ-PGA應用於香蕉貯藏及加工之研究。 香蕉為典型之低温敏感水果，貯存温度低於12℃則發生寒害。香蕉不耐貯存，採收後常温貯存約15天即無商品價值。目前國產香蕉內銷約佔95%；易發生產銷失衡，本研究擬由延長香蕉貯藏期，增加加工利用性進行探討。 香蕉貯藏方面，以35μg/ml AFP浸漬液浸漬全綠香蕉4小時， 貯存於12~15℃，可延長貯存期至38天，較常温貯藏控制組增加22天；較12~15℃貯藏控制組增加8天貯藏期。 香蕉加工方面，香蕉泥褐變是香蕉加工一大不利因素，本研究以半胱氨酸(cysteine) 600ppm及抗壞血酸(Ascorbic acid) 900ppm 可有效抑制香蕉泥褐變。並以此配方進行後續香蕉冰淇淋、冷凍香蕉、香蕉乾加工試驗。 香蕉冰淇淋添加聚麩胺酸（γ-PGA）具有保健功能，使用於冰淇淋可改善冰淇淋的品質，且於貯存温度發生變化後仍能維持其品質。低脂香蕉冰淇淋添加35μg/ml AFP及0.3%γ-PGA，進行消費者喜好性及接受性感官品評，經65位品評員品評結果，本實驗所開發之低脂、健康且具機能性香蕉冰淇淋已可上市。冷凍香蕉浸漬35μg/ml AFP及0.3%γ-PGA亦已可上市。 本研究結果顯示，抗凍蛋白可延長香蕉貯藏期；抗凍蛋白及聚麩胺酸可改善冷凍香蕉、香蕉冰淇淋之品質。此研究結果配合加工廠量能、行銷等相關配套措施得宜，預期可幫助農民、政府減緩香蕉產銷失衡問題，創造另一商機。另外亦可應用於其他食品、農產品之延長貯藏期、改善食品品質試驗。

Antifreeze proteins (AFPs) were found in a variety of organisms who lived in supercooling conditions. AFPs modify the shape of ice crystal, inhibit ice qrowth, repress the ice crystals from recrystallization and lower the body fluids freezing point of organisms. In this study, the recombinant AFP (rAFP) was expressed extracellularly by a GRAS host Bacillus Subtilis. The rAFP was approved by FDA as Food Contact substance. Poly-γ-glutamate (γ -PGA) characteristics includ thickening, emulsion, gel, film, frost, adsorption, moisture, bonding, biodegradable and dissolution of blood clots. So far, γ –PGA has been applied in the food, healthy food, medicine, cosmetics, environmental protection, animal products and agriculture.In this study, γ-PGA was produced from constructed Bacillus subtilis PGA 6-2 transformants, and rAFP and γ-PGA were used in banana storage and processing. Banana is a typical low-temperature-sensitive fruit. Banana preceded chilling injury when stored below 12 ℃. Banana usually lost the value of commodities under 15 days room temperature storage after harvest. In Taiwan, 95% domestic banana suffers from imbalance of production and marketing. In this study, attemps of banana storage extension and banana processing to increase the utilization were preceded. In the experiment of banana storage, all-green bananas were immersed into coating solution containing 35 μg/ml AFP for 4 hours and then stored at 12 to 15 ℃. The storage period that was 22 days and 8 days longer than control bananas that was stored at room temperature and 12 to 15 ℃,respectively. In banana processing, browning of the bananas is the most unfavorable factors. Inhibition of browning could be achieved by adding 600ppm cysteine and 900ppm ascorbic acid. The inhibiters were used in following banana ice cream and iced banana processing test. The 35μg/ml AFP and 0.3% γ-PGA, were used in banana ice cream and frozen banana processing.Consumer preferences and acceptance were evaluated by 65 judges’ consumer sensory test. Results showed that the formula of low-fat, healthy and functional banana ice cream are marketable. Frozen banana immersed with 35μg/ml AFP and 0.3% γ-PGA is marketable as well. The results of this study showed that the antifreeze proteins and poly-γ-glutamic acid can be used to extend the storage period of bananas and improve the quality of frozen banana and banana ice cream. This outcome is expected to help farmers and the government to improve the banana production and marketing imbalances and to create more business opportunities. In addition, this outcome can also be applied to other food and agricultural products to extend the storage period and improve frozen food quality.