Effect of thermal treatments on the degradation of antibiotic residues in food

The thermal stability of antibiotics commonly detected in food is reviewed. To quantify degradation, 2 major techniques have been reported: liquid chromatography-based methods and microbiological tests. As the degradation products may also display some antimicrobial activity, microbiological tests may not be considered accurate analytical methods for quantifying antibiotic residues' degradation. Degradation percentages are summarized for different antibiotics and for various media (water, oil, milk, and animal tissues). Studies presented in the literature confirm that the thermal degradation of β-lactams, quinolones, sulfonamides, and tetracyclines can be described using a first-order kinetic model. Degradation rates, k, derived for this model for liquid matrix (water) at 100 °C, followed the general trend amongst antibiotic classes: β-lactams = tetracyclines (most heat-labile) > lincomycin > amphenicols > sulfonamides > oxfendazole > levamisole (most heat-stable). Although thermal processing results in a decrease in the concentration of parent antibiotic residues, degradation by-products have not been properly characterized to date. As some of these products were shown to be hazardous, further investigation is needed to determine their impact on food safety and human health. It is therefore currently difficult to definitively conclude whether or not antibiotic degradation during food processing is necessarily beneficial in terms of food safety.

本文综述了食品中常见检出的抗生素的热稳定性。为定量表征抗生素的降解过程，现有研究已报道两类主流检测技术：基于液相色谱的分析法与微生物检测法。由于降解产物同样可能具备一定抗菌活性，因此微生物检测法无法作为准确定量抗生素残留降解情况的可靠分析方法。研究针对不同种类抗生素及多种基质（水、油脂、牛奶与动物组织）总结了其降解率数据。已有文献研究证实，β-内酰胺类（β-lactams）、喹诺酮类（quinolones）、磺胺类（sulfonamides）以及四环素类（tetracyclines）的热降解过程均可采用一级动力学模型进行描述。针对100℃下液态基质（水）中该模型推导得到的降解速率常数k，不同抗生素类别间呈现如下普遍规律：β-内酰胺类=四环素类（热稳定性最差）＞林可霉素＞酰胺醇类（amphenicols）＞磺胺类＞奥芬达唑（oxfendazole）＞左旋咪唑（levamisole，热稳定性最优）。尽管热加工过程可降低母源抗生素残留的浓度，但截至目前，降解副产物的结构特征尚未得到充分表征。由于部分此类降解产物已被证实具有危害性，因此亟需开展进一步研究以明确其对食品安全与人类健康的潜在影响。因此，目前尚无法确切判定食品加工过程中抗生素的降解是否必然对食品安全有益。