ISEP - DM – Biorrecursos
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- Ferramenta ótica para controlo alimentar: avanços no perfil metabólico das aminas biogénicas e validação de um biossensor óticoPublication . Teixeira, Ana Beatriz Matias; Morais, Simone BarreiraDuring the previous decade, biosensors emerge as a very versatile methodology, in part because they allow the use of nanomaterials, functionalization with different compounds, and immobilization of enzymes, microorganisms, antibodies, and nucleic acid. Therefore, the main objective of this master thesis was to advance in food security comprehension through the development of an optical biosensor and to evaluate the metabolic pathways of biogenic amines in food products. The strategy used was based on a new and highly sensitive methodology that included the development of an optical biosensor specific for hydrogen peroxide detection. The sensing methodology behind the developed optical biosensor is based on the detection of a luminescence signal from the chemical reaction within a solid cellulose membrane with a round shape of 10 millimeters in diameter. The biosensor optimization was conducted on an experimental level (e.g., cellulose membrane chemical constituents’ optimization, enzymatic reaction parameters, range of H2O2 detection, time of chemiluminescence and enzymatic reaction, and physical aspects of the biosensor) until the final prototype was established. A linear response was attained for pure water from 0.0001% to 0.001 %w/w of H2O2, with a limit of detection of 2.0x10-5% w/w. A coefficient of determination, R2 , greater than 0.99 was achieved, with a relative standard deviation (RSD) not exceeding 10%. The optimized biosensor was successfully applied to milk samples adulterated with H2O2, where higher response levels were obtained for free fat milk. In the analyzed milk samples, the lowest concentration detected was 0.001%w/w for raw milk and 0.002% w/w for skim milk, semi-skimmed milk and whole milk. Concentrations of H2O2 of 0.001% w/w to 0.005% were detected and the method was calibrated for different types of milk, proving that limit of detection and linearity range of the proposed method are suitable for the analysis of milk samples in-situ, which can add value to the food fraud department. A preliminary study of BAs determination by GC-MS was carried out. This allowed the detection of four biogenic amines [histamine (HIS), putrescine (PUT), cadaverine (CAD) and tyramine (TYR)], which can be further applied to its determinations in real samples, for biosensor validation purposes. Since these compounds must be derivatized previously, the silanization method was the chosen method for amines derivatization. Finally, the physico-chemical characteristics and microbiological quality of chicken breast meat were evaluated. Samples stored over 12 days at 8ºC, had significant effects on the physico-chemical characteristics and microbiological quality of meat samples. Microbial counts increased instantaneously, increasing pH values and reducing the color parameters (lightness, yellowness, and redness), indicating breast chicken deterioration. From that study, it was concluded that the evolution of microbial content in chicken meat was coherent with both pH and color determinations, that are dependent on microorganisms grow. The information gathered during this work timeline was useful for the construction of the Food quality chart. This last can be used to renovate and upgrade the existing BAI index, once it gathers and dispose of the information on a new form. On the other hand, it is a practical and user-friendly tool that can be used in the industrial context.