**1. Introduction**

Livestock and poultry meat, rich in protein, fat, minerals and vitamins, is an important source of nutrients for the human body [1]. In recent years, livestock and poultry farming have grown rapidly worldwide. However, the industry is facing problems such as bacterial, viral and parasitic infections. If not given prompt treatment, they may lead to the occurrence of zoonotic diseases during the breeding process or through the food chain and cause severe economic losses. Thus, antibiotics are widely used in animal production to prevent and treat bacterial diseases, as well as to promote growth and improve feed utilization. They provide convenience to modern intensive farming and can meet the demand for livestock and poultry production and market consumption [2].

Amphenicols, mainly including chloramphenicol (CAP), thiamphenicol (TAP) and florfenicol (FF), are a class of highly potent and economic antibiotics with broad-spectrum

**Citation:** Wu, M.; Cheng, X.; Wu, X.; Qian, H.; Wang, W. Effect of Cooking Methods on Amphenicols and Metabolites Residues in Livestock and Poultry Meat Spiked Tissues. *Foods* **2022**, *11*, 3497. https:// doi.org/10.3390/foods11213497

Academic Editor: Jean-Paul Vernoux

Received: 1 September 2022 Accepted: 1 November 2022 Published: 3 November 2022

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antimicrobial activities that are widely used in livestock and poultry breeding and production [3,4]. The first generation of amphenicols, CAP, has many toxic side effects and can disrupt the body's hematopoietic function and trigger aplastic anemia (a condition in which the bone marrow fails to produce enough new cells to replenish the blood cells). It has been banned by China, the European Union, the United States and other countries and organizations for treating food-producing animals [5]. The para-nitro group on the aromatic ring of CAP is the leading group that causes aplastic anemia. As a derivative of CAP, TAP replaces the *p*-nitro (-NO2) of CAP with *p*-methylsulfonyl (-SO2CH3). The two have a similar antibacterial spectrum and antibacterial effect, but TAP is much less toxic than CAP. FF is a third-generation amphenicol drug obtained by replacing the C-3 hydroxyl group (-OH) of TAP with the fluorine atom. The presence of the fluorine atom reduces the number of sites for the acetylation of CAP and TAP by bacteria, thus enhancing the acetylation effect of the drug against bacterial resistance. FF has better antimicrobial activity, resistance and safety than TAP and CAP and is an animal-specific broad-spectrum antibiotic. The metabolic response of FF in the tested animals is shown in Figure 1, with the main metabolite being florfenicol amine (FFA) [6]. TAP and FF have completely replaced the use of CAP in food animals due to their excellent antibacterial effect and higher safety. Unfortunately, these antibiotics are often used irrationally, resulting in excessive residues in the tissues of the animals to be consumed, posing a significant challenge to food safety [7,8]. To protect consumers from potential health-related problems, many countries and organizations have established maximum residue limits (MRLs) for amphenicols in animal-origin foods (Table 1).


**Table 1.** Maximum residue limits (MRLs) for amphenicols and metabolites in animal-derived foods.

CAP: chloramphenicol; TAP: thiamphenicol; FFA: florfenicol amine; U.S.: the United States; EU: the European Union.

To date, food safety risk assessment, market supervision and the import/export certification of veterinary drug residues in livestock and poultry meat have been carried out on unprocessed products. However, most animal-derived foods are ordinarily cooked or processed prior to consumption to improve their nutrient digestibility, palatability and shelf-life [8]. Studies have shown that cooking not only affects nutrients such as protein and fat in livestock and poultry meat but also leads to changes in drug residue concentrations, chemical structures and their solubility in the tissues [9–11]. Therefore, to accurately assess the dietary exposure levels of drug residues, it is crucial to study the impacts of cooking methods on the residues of amphenicols and metabolites in livestock and poultry meat. Currently, there is minimal research on the changes in amphenicol antibiotic residues in livestock and poultry meat processing at home and abroad. The available studies also have problems, such as the single selection of meat species and cooking methods and unsystematic studies.

**Figure 1.** Florfenicol (FF) metabolic pathways.

In this study, we added certain concentrations of CAP, TAP, FF and FFA standard solutions to the muscle of negative livestock and poultry (pig, cattle, sheep and chicken) and made meat blocks that were 18 g in size, had good drug homogeneity and were processed to simulate domestic cooking such as boiling, deep-frying and microwaving. Our aim was to assess the effects of three processing methods under different temporal conditions on the residue levels of amphenicols and metabolites in livestock and poultry meat. The development of this study may provide some data basis and theoretical support for the accurate assessments of meat safety and the risk of dietary exposure to amphenicol antibiotics.
