Development of analytical methodologies for the monitoring of contaminants and residues in milk and dairy products
- Autores: Ahmed Mohammed
- Directores de la Tesis: Ana María García Campaña (dir. tes.), Laura Gámiz-Gracia (dir. tes.)
- Lectura: En la Universidad de Granada ( España ) en 2017
- Idioma: inglés
- Títulos paralelos:
- Desarrollo de metodologías analíticas para el control de contaminantes y residuos en leche y productos lácteos
- Tribunal Calificador de la Tesis: Alberto Fernández Gutiérrez (presid.), Carmen Cruces Blanco (secret.), Francisco Javier Arrebola Liebanas (voc.), Jose Fernando Huertas Perez (voc.), Mercedes de Frutos Gómez (voc.)
- Programa de doctorado: Programa de Doctorado en Química por la Universidad de Granada
- Materias:
- Enlaces
- Tesis en acceso abierto en: DIGIBUG
- Resumen
Milk and dairy products are very rich in nutrients and thus provide an ideal growth environment for food-borne pathogens. Moreover, milk and dairy products can also contain chemical hazards and residues mainly introduced through the environment, animal feedstuffs, animal husbandry and industry practices.
This Thesis is focused on chemical hazards, specifically on contaminants (such as mycotoxins) and residues of other chemicals (as pesticides or antibiotics), used or added during the animal production or manufacturing processes, susceptible to contaminate milk and derived products. In addition, considering the increasingly consume of vegetable milks (most of them based on cereals), this commodity has been included in part of the study together with milk and dairy products. Mycotoxins are highly toxic secondary metabolites produced by certain fungi that grow on agricultural products. Ingestion, inhalation or skin absorption of mycotoxins can cause illness or even death in both humans and animals. The presence of mycotoxins in milk is a topic of great interest, since milk is an important food for adults and children. Given the variety of mycotoxins that may occur in the diet of animals, the number of studies related to the transfer of these compounds to dairy products is very limited. Moreover, mycotoxins can also contaminate vegetable-derived milks. Studies on mycotoxins in these matrices are scarce, although the raw products (soy, oat, rice, etc.) are frequently contaminated.
The environment can have an effect on milk production through environmental contaminants such as pesticides, extensively used for agricultural activities, which may lead to residues in milk. Among the different families of pesticides, carbamates are commonly used as insecticides, and their presence in foods can produce adverse health effects, as they have high acute toxicity. Thus, their presence on milk and dairy products as a consequence of feeding the animals with contaminated food or water is a matter of concern.
With regard to veterinary antibiotics, their residues in foods of animal origin and specially milk and dairy products, have adverse health effects. Thus, the development of antibiotic resistance in bacteria has long been attributed to the overuse of antimicrobials in human medicine but the relationship between the use of antimicrobials in animal husbandry and the antibacterial resistance in humans is also the subject of much concern.
Referring to these problems and taking into account the last technical advances in terms of efficiency and miniaturization, different separation techniques, such as HPLC, UHPLC and also CE have been assessed, coupled to detection techniques such as FLD, MS/MS and Q-TOF-MS/MS. In addition, alternative sample treatments based on recent miniaturized techniques and new sorbents, have been proposed, making possible an increased efficiency and sample throughput.
As a summary, the Thesis compiles the following works: In the first chapter, HPLC-PI-FLD has been proposed for sensitive, simple, and rapid determination of the five aflatoxins regulated by European legislation (aflatoxin M1, B1, B2, G1 and G2) in different types of yogurt (natural, skim and liquid), using DLLME as an alternative sample treatment, scarcely explored for these compounds. This procedure allowed the simultaneous precipitation of proteins and extraction, shortening the analysis time.
In the second chapter, a UHPLC-MS/MS method to determine seven Fusarium toxins (fumonisin B1, fumonisin B2, HT-2 and T-2 toxin, zearalenone, deoxynivalenol, and fusarenon-X) was developed. In this case, different types of vegetable milks (oat, soy, rice and birdseed milks) were the target matrices. The sample treatment consisted of a SALLE with no further clean-up. Moreover, a study of the occurrence of these contaminants in market samples was carried out.
In the third chapter, a simple and efficient method for the determination of twenty eight carbamates in high-fat cheeses was proposed. The methodology was based on a QuEChERS procedure using a new sorbent (Z-Sep+) followed by UHPLC-MS/MS determination. The method has been validated in different kinds of cheese (Gorgonzola, Roquefort and Camembert).
In the fourth chapter, an analytical method for the determination of eleven aminoglycosides in different types of milk and milk-based functional products has been optimized and validated. A HILIC column was proposed for the separation of analytes by UHPLC–MS/MS. Also, a MIPs has been used for the SPE of the analytes, in order to achieve high selectivity in the sample treatment.
In the last chapter, a new analytical method based on CE-MS/MS for the identification and simultaneous quantification of fifteen antibiotics (seven quinolones and eight tetracyclines) in milk samples has been validated. Detection using an Accurate-Mass Quadrupole Time-of-Flight (Q-TOF) was used. A SPE method using the new Oasis® HLB PRiME cartridge was applied for clean-up. This work was developed during a stay in the research group of Prof. Antonio Molina (University of Jaen).
