運用辛酸/幾丁聚醣/明膠之可食膜提升肉品安全性與架儲期

Abstract

長久以來，肉類產品一直是人們動物性蛋白質的主要來源，是飲食中不可或缺的食物之一。然而肉品在屠宰及儲藏過程中，可能因為品質下降 （如：脂質氧化、腐敗）和病原菌交叉汙染等問題，影響架儲期和安全性，對於消費者和零售商而言是一大隱憂。根據我國食藥署的食品中毒事件統計資料，肉類在各類食品中排名第三，且近年來肉品的人均攝食量逐年攀升，亦可能導致肉品引起的食源性疾病風險與發生率隨之上升，因此相關業者必須尋求更完善且有效的方法，以滿足大衆對肉品安全和架儲期的需求，亦是保障公共衛生與健康的重要課題。本研究旨在開發以幾丁聚糖 (CHI)、明膠 (GEL) 和辛酸 (CA) 為基礎之可食用複合塗膜，並測試其在LB培養基 和新鮮牛肉基質 (有氧包裝) 之抑菌、抗氧化和抗病原菌功效。此複合塗膜的保存特性測試，是將具有塗膜之新鮮牛肉儲存在冷藏溫度 (4 ℃) 下20天，評估其對於抑制鮮肉之微生物腐敗、脂質氧化和品質流失上的影響。而複合塗膜的抗病原菌性能，則是將新鮮牛肉接種病原菌之後再塗膜，然後將肉品置於冷藏 (4 ℃) 和 10 ℃ 低溫下儲存7天，藉以評估塗膜對於病原菌生長之影響。 在研究初始階段，先以培養基測定了CA對常見肉類病原菌 (即金黃色葡萄球菌、大腸桿菌O157:H7、鼠傷寒沙門氏桿菌和綠膿桿菌) 的最小抑菌濃度和最小殺菌濃度，以篩選最佳CA濃度加入幾丁聚糖-明膠 (CHI-GEL) 之複合膜中。培養基實驗表明1% CHI - 3% GEL複合膜對於所有病原菌的生長抑制超過3 log CFU/mL。若進一步添加0.25%或0.5% CA能夠大幅提升抑菌能力到4至9 log CFU/mL。在新鮮牛肉的塗膜試驗中也觀察到類似的結果，其中CHI-GEL複合膜對所有病原菌抑制功效隨著CA的添加而加强，達到超過3 log CFU/g。研究結果顯示出CA和CHI-GEL膜之間具有協同的抗菌活性。此外，CHI-GEL-CA複合膜在維持肉品品質方面的效果很顯著，包括：延遲腐敗菌的生長、減少過氧化物質的産生，降低pH和顔色的變化。最終結果顯示未塗膜的肉品對照組、CHI-GEL複合膜組和CHI-GEL-CA複合膜組對新鮮牛肉的保質期分別為：10天、15天和20天。另外，此複合膜也具有良好的穩定性和成本效益，以確保在肉品的適用性和實用性。綜上所述，本研究發現含有0.5% CA的CHI-GEL複合膜，是一種前瞻性且極具應用價值的可食性包膜，未來可用於確保新鮮肉品在有氧包裝下的安全性並延長其架儲期。

Meat products have long been a staple food in people’s diets as the primary source of animal protein. However, during processing and storage, the problems related to quality degradations (i.e., lipid oxidation, spoilage) and pathogen cross-contamination creates shelf life and safety concern for consumers and retailers alike. According to the Taiwan Food and Drug Administration, foodborne outbreaks related to meat products rank 3rd among all food types. Moreover, recently, there has been a continual increase in the average meat intake of the people in Taiwan, which can lead to higher rates of foodborne outbreaks. Therefore, finding effective treatments are important matters for food safety practitioners, to meet the public demand for safe and long shelf life meat products. The objective of this study was to determine the antimicrobial, antioxidant, and antipathogenic activities of a newly developed edible composite coating comprised of chitosan (CHI), gelatin (CHI-GEL), and caprylic acid (CA), under growth medium (Luria-Bertani broth) and aerobically packaged meat (fresh beef) matrix. The preservation properties of the coatings were evaluated based on the extent of microbial spoilage, lipid oxidation, and quality loss in fresh meat stored at refrigerated temperature (4 °C) for 20 days. The inhibitory properties of coatings were assessed based on pathogenic bacterial growth in inoculated meat stored at refrigerated (4 °C) or abusive temperature (10 °C) for seven days. In the preliminary phase of the study, the minimum inhibitory concentration and minimum bactericidal concentration CA against common meat pathogens (i.e., Staphylococcus aureus, Escherichia coli O157:H7, Salmonella Typhimurium and Pseudomonas aeruginosa) were determined to select the ideal CA concentration to be incorporated in CHI-GEL composite coating. The growth medium experiments showed that 1% CHI-3% GEL composite coating effectively inhibited all pathogenic growth by > 3 log CFU/mL. Further addition of 0.25% or 0.5% CA was able to enhance the antipathogenic activities, inhibiting growth by 4 to 9 log CFU/mL. Similar results were observed in the fresh beef application, wherein the suppressive effects of CHI-GEL composite coating against all pathogen growth were increased with CA addition reaching > 3 log CFU/g. The results indicated synergistic antipathogenic activity between CA and CHI-GEL coating. Moreover, the CHI-GEL-CA composite coating also achieved satisfactory results in preserving meat quality, with indications of delayed spoilage, reduced thiobarbituric acid reactive substances (TBARS) production, less pH change, and lowered color loss. The overall meat shelf life was determined to be 10 days, 15 days, and 20 days for uncoated control, CHI-GEL coating, and CHI-GEL-CA coatings, respectively. Furthermore, the developed composite coating also had good stability and was very cost-effective, assuring their applicability and practicality in meat products. This study suggests that CHI-GEL composite coating containing 0.5% CA can be developed as a prospective and practical method for ensuring the safety and shelf life of aerobically packaged fresh meat products.