不同处理方法对葡萄牙牡蛎体内菌群净化效果的比较

牡蛎肉味鲜美,营养丰富,经济价值较高,素有海洋"牛奶"之美称。然而,由于养殖环境的污染,国内多数养殖牡蛎体内的大肠杆菌含量超标,危害公民健康。因此,研发养殖牡蛎净化技术日显重要。为此,本文以我国南方重要的养殖牡蛎(葡萄牙牡蛎,也称福建牡蛎)为对象,设计了三种净化方法 (大蒜素灭菌法、紫外灭菌法、混合灭菌法(大蒜素+紫外线)先灭菌处理海水6h,然后将牡蛎养殖灭菌后的海水中,并在0 h、12 h和24 h时分别对其软体组织进行取样,检测菌落总数和大肠杆菌含量,以探求最佳净化牡蛎方法。结果显示,三种方法都能够对牡蛎体内的菌落总量和大肠杆菌含量起到显著的净化作用。比较而言,大蒜素净化效果最佳,经12 h和24 h的净化后,牡蛎体内的大肠杆菌含量(MPN/100 g)由最初的2 307降至为240和189,显著低于紫外灭菌法的744和322以及混合灭菌法的384和359。经大蒜素净化24 h后,牡蛎体内的大肠杆菌含量为189 MPN/100 g,低于欧盟和我国双壳贝类养殖水域划分依据中规定的大肠杆菌含量≤230MPN/100 g时可以直接上市并供生食的标准。

Comparison of purging effects for Escherichia coli in the oyster Crassostrea angulate using different methods

The oysters are of high economic value, which are also called " Ocean Milk" because of their rich in nutrition. However, most of the cultured oysters in China cannot be directly eaten being excessive in Escherichia coli which harm human health. So, it is becoming important to study techniques on purging E. coli in oysters. In this study, three kinds of methods were used to purge E. coli in the oyster Crassostrea angulate. Firstly, sand filtration of seawater was sterilized for 6 hours with garlicin, UV and mixed (garlicin plus UV), respectively. Then, cleaned oysters were cultured in sterilized seawater and their soft tissues were sampled at 0h, 12 h and 24 h to determine total numbers of bacterial colony (cfu/100 g) and total numbers of E. coli (MPN/100 g). The results showed that numbers of bacterial colony and total numbers of E. coli were both significantly purged by three kinds of methods. In comparison with the other two methods, the garlicin sterilization was the best purging method. After 12 h and 24 h purging with the garlicin, the total numbers of E. coli (MPN/100 g) was decreased from 2 307 at 0h to 240 at 12h and 189 at 24 h, which was significantly lower than 744 at 12 h and 322 at 24 h with UV sterilization, and which was also significantly lower than 384 at 12 h and 359 at 24 h with mixed sterilization, respectively. The present result that the total numbers of E. coli (MPN/100 g) in the oyster was 189 after 24 h purging with the garlicin also significantly lower than 230 which was required by EU and China in classification of bivalve shellfish harvesting area and shellfish sanitary requirement. Therefore, the oysters after 24h purging with the garlicin can be sold directly to market and be also raw eaten.