農業部水產試驗所全球資訊網

本土養殖牡蠣主要產區集中於彰、雲、嘉、南等縣市沿近海域，受惠於營養鹽的供給及豐富的微藻供應鏈，造就國產牡蠣的肥美，然地狹人稠所產生的污染也直接或間接影響牡蠣食用的安全性。為提升國產牡蠣的衛生安全及品質，本研究組裝紫外線燈、冷卻系統及循環過濾槽成60 L的小型淨化系統來淨化帶殼牡蠣，並探討淨化前、後對其微生物、鮮度、風味及冷藏架售期之影響。結果顯示：牡蠣淨化前總生菌及腸炎弧菌，分別為1.63 × 10⁵ cfu/g及 > 1,100 MPN/g，大腸桿菌群及沙門氏菌皆為陰性；淨化處理96 hr可提升牡蠣品質至符合冷凍生食用魚介類之標準 (總生菌 <1.0 × 10⁵ cfu/g) 及生鮮即食水產品之限量標準 (腸炎弧菌 < 100 MPN/g，沙門氏菌及單核球增多性李斯特菌陰性)。在風味上，相較於未淨化組，淨化處理 (72 hr) 之牡蠣肝醣、脂肪酸及游離胺基酸含量分別降低了73.5% (p < 0.05)、46.4%及24.2% (p < 0.05)。進一步分析呈味胺基酸組成，其中生牡蠣在鮮味、甜味及苦味胺基酸含量上，淨化處理後分別減少18.9%、27.4%及13.4%，然而相較於未淨化的熟牡蠣，淨化處理則顯著改善蒸煮後熟牡蠣呈味胺基酸的流失。比較淨化處理對牡蠣於冷藏期間之衛生安全，顯示未處理組及淨化組牡蠣預估分別於冷藏第12.3天及33.4天將超過冷凍鮮魚介類可食之標準。上述結果顯示：淨化處理國產帶殼牡蠣不僅有助於提升牡蠣衛生安全符合生食用魚介類之標準，亦能減少熟食牡蠣風味的流失，並延長帶殼牡蠣冷藏之架售期。

摘要abstract(英) The local oyster farming industry in Taiwan is located along the coastal waters of Changhua, Yunlin, Chiayi, and Tainan. The oysters here are plump thanks to the nutrients, salts, and abundant microalgae growth. However, frequent contamination from human activities also directly or indirectly triggers food hygiene concerns. To improve the quality and safety of local oysters for consumption, a 60-liter small depuration system consisting of an ultraviolet light system, a cooling system, and a circulating filter tank was installed in-house to purify the oysters. The effects of depuration on oyster hygiene, flavor, and fresh-keeping of the were investigated. The results showed that total plate count (TPC) and microbial count of Vibrio parahaemolyticus in the control (non-depuration) group was 1.63×105 cfu/g and >1100 MPN/g, respectively, both the coliform and Salmonella levels were negative. A 96-hr depuration treatment promoted local oysters' to meet the legal hygiene standard of raw seafood for human consumption (TPC <1.0×105 cfu/g and Vibrio parahaemolyticus <100 MPN/g). In the flavor analysis, the glycogen, total fatty acids, and total free amino acids of the oysters had decreased by 73.5% (p < 0.05), 46.4%, and 24.2% (p < 0.05), respectively after 72-hr depuration. Moreover, the levels of umami and sweet and bitter amino acids on the raw oyster from the depuration group decreased by 18.9%, 27.4%, and 13.4%, respectively. However, the depuration significantly improved the loss of amino acids (p < 0.05) from oyster cooking. Comparing the hygiene and safety of the non-depurated and depurated oysters under refrigeration, the oysters met the legal standard for edible seafood for 12.3 and 33.4 days, respectively. Depuration treatment marked an improved oyster quality for raw consumption, better flavor retention in the cooked oysters, as well as extended refrigerated shelf life, thus increasing the sales revenue of locally produced oysters.