Depuration of naturally contaminated farmed edible oyster Crassostrea madrasensis was evaluated using fill and draw depuration system (FDDS) and flow-through depuration system (FTDS) to ensure food safety in oyster consumption. Depuration conducted at room temperature with seawater salinity ranges 30–35 psu and pH of 7.5–8.0. Prior to depuration, the levels of faecal indicator bacteria (<230 MPN/100 g) and toxic metals including Pb (2 mg/kg) and Cu (3 mg/kg) were above the acceptable limits. Other metals such as Ni, Co, Fe, Mn and Zn were also investigated. The results of the investigation pointed out that, both the depuration methods could significantly (p < 0.01) reduce the bacterial and heavy metal contamination from oyster samples, though there was no significant difference between the two methods with respect to efficacy (FDDS and FTDS). Significant differences were also found in reduction of toxic metals such as Pb and Cu (p < 0.05) as a function of depuration duration. To reduce the toxic Pb levels to the acceptable limit, 16 h of depuration was required in FTDS whereas FDDS oysters required 48 h of depuration. The FTDS and FDDS required 24 and 36 h of depuration respectively to reach the acceptable limit of E. coli. Visualisation by PC plots clearly separated the investigated samples according to depuration method and duration, thus indicating the effect of treatment methods on depuration. We recommend FDDS for bacterial and heavy metal depuration in oysters owing to its comparatively lower cost, even though FTDS depuration was faster in reducing the bacterial and metal contents in oysters.

使用填充和抽取净化系统 (FDDS) 和流通净化系统 (FTDS) 对自然污染的养殖食用牡蛎Crassostrea madrasensis 的净化进行了评估，以确保牡蛎消费中的食品安全。在室温下进行净化，海水盐度范围为 30-35 psu，pH 值为 7.5-8.0。在净化之前，粪便指示菌 (<230 MPN/100 g) 和包括 Pb (2 mg/kg) 和 Cu (3 mg/kg) 在内的有毒金属的水平高于可接受的限度。还研究了其他金属，例如 Ni、Co、Fe、Mn 和 Zn。调查结果表明，两种净化方式均能显着（p < 0.01) 减少牡蛎样品中的细菌和重金属污染，尽管两种方法（FDDS 和 FTDS）在功效方面没有显着差异。还发现了 作为净化持续时间的函数的有毒金属（例如 Pb 和 Cu ）的减少量存在显着差异（p < 0.05）。为了将有毒 Pb 水平降低到可接受的限度，FTDS 需要 16 小时净化，而 FDDS 牡蛎需要 48 小时净化。FTDS 和 FDDS 分别需要 24 小时和 36 小时的净化时间才能达到大肠杆菌的可接受限度. 根据净化方法和持续时间，PC 图的可视化清楚地分离了研究的样品，从而表明处理方法对净化的影响。我们推荐 FDDS 用于牡蛎中的细菌和重金属净化，因为其成本相对较低，尽管 FTDS 净化在减少牡蛎中的细菌和金属含量方面更快。