Repository logo

Browsing by Author "Ramos, Sara Miguel do Vale Teixeira"

Now showing 1 - 1 of 1
  • Desenvolvimento e otimização de extração de antioxidantes de matrizes alimentares por QuEChERS
    Publication . Ramos, Sara Miguel do Vale Teixeira; Ferreira, Maria João Dantas Ramalhosa
    Nowadays there is a global trend towards the efficient utilization of natural resources, among others those that are found in food consumed by humans. This situation happens not only as a method to prevent pollution, but also as a practice to benefit from the compounds in several nourishments that can bring benefits to human health. Taking that into consideration, this work intended to evaluate the antioxidant capacity and phenolic profile of apple species available in the Portuguese market, as apple is one of the most consumed fruit around the world. For this purpose, the extraction conditions of apple antioxidants by QuEChERS were developed and optimized. The results obtained were compared to a conventional extraction method so that it was possible to determine which parameters had the greatest influence in the extraction yield. The extraction efficiency was evaluated by the spectrophotometric methods, total phenolic content (TPC), total flavonoid content (TFC) and ferric reducing antioxidant power (FRAP), and the phenolic profile was assessed by high performance liquid chromatography with diode array detection (HPLC-DAD). In comparison with the conventional extraction, the higher results were obtained with the QuEChERS extraction with salt S1, composed by magnesium sulphate and sodium acetate, which was able to promote the extraction and therefore the amount of extracted phenolic compounds. For the solvents tested, water was the extractor solvent that enabled to obtain the highest yield, either by conventional extraction (TPC – 154.4 ± 5.9 µg GAE/g; TFC – 98.7 ± 7.3 µg EE/g; FRAP – 71.7 ± 1.4 µg AAE/g) or by QuEChERS extraction (TPC – 505.5 ± 63.7 µg GAE/g; TFC – 881.6 ± 69.9 µg EE/g; FRAP – 25.7 ± 2.5 µg AAE/g). Regarding the phenolic profile assessment, in the QuEChERS extract was possible to identify several acids, namely chlorogenic, caffeic, vanillic, p-coumaric acid and sinapic acids and only the flavonoid naringin. In the conventional extracts, the phenolic compounds identified were the same as for the QuEChERS extracts, although in the extract from acetonitrile solvent it was possible to quantify naringin and β-resorcyclic acid with the amounts of 0.64 ± 0.03 and 1.94 ± 0.09 mg/L, respectively.
    2016Master thesis Open access Show more