Speciation copper and zinc in coconut water and the influence of the pasteurization process on these species

Author(s)

Rita de Cássia Siloto

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2005-03-22

Examining board members

Pedro Vitoriano de Oliveira; Fabio Augusto; Maria Teresa Machini de Miranda

• Advisor: Pedro Vitoriano de Oliveira

Abstract

Coconut water is a natural isotonic, nutritive and low caloric drink. Its chemical composition is quite complex, some of the main compounds are sugars and minerais and, in smaller amounts fat and compounds of nitrogen. The coconut water preservation outside the fruit, maintaining its physical and organolépticas properties is a big challenge. Pasteurization has been used as one of the most common preservation processes. However, little knowledge exists about the influence of preservation processes over coconut water chemical composition. This way, the aim of this work was to investigate the chemical species of Cu and Zn in coconut water and evaluate the influence of pasteurization over these species. For this, many procedures such as, pH measurements, c10ud point extractions, solvent extraction, ultrafiltration, measurement of total protein concentration, sodium dodecil sulphate poliacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography were executed. The Cu and Zn determinations were made in a whole coconut water and in its different fractions, obtained by the separation techniques by using electrothermal atomic absorption spectrometry. The results of Cu, Zn and protein determinations showed that there is a big variation between different fruits. Results obtained by ali techniques used showed that Cu is, preferentially Iinked to big molecules and Zn is associated to small molecules. The results of gel filtration chromatography associated to the concentration of Cu and Zn in the collected fractions showed the strong possibility of Iinkage of these elements with proteins. The pasteurization did not cause significant changes in the total proteins concentration, however, the changes observed indicated the break in week chemical connections, probably in proteins (agglomerations of high molecular mass), increasing the abundance of small proteins (Iow molecular mass). (AU)