Cu, Fe, Mn and Zn distribution in protein fractions of Brazil-nut, cupuassu seed and coconut pulp by solid-liquid extraction and electrothermal atomic absorption spectrometry

摘要

In this work Cu, Fe, Mn and Zn were determined in extracts of Brazil-nut (Bertholletia excelsa), cupuassu (Theobroma grandiflorum) seeds and coconut (Cocos nucifera) pulp, using solid-liquid extraction and electrothermal atomic absorption spectrometry. Different extractant solutions (mixture of methanol and chloroform 1:2 v/v, water, 0.5 mol L-1 NaCl, 70% v/v ethanol, and 0.5 mol L-1 NaOH) were used for extracting lipids, albumins, globulins, prolamins and glutelins, respectively. The protein concentrations determined in Brazil-nut are higher than those observed for cupuassu and coconut pulp. The analysis of lipid fractions reveals high concentations of Fe in Brazil-nut and cupuassu seed and Zn in coconut pulp. For Brazil-nut, these elements are mainly associated to albumin, globulin and glutelin fractions. The same behaviour was not observed for cupuassu seed and coconut pulp. The element concentrations changed in each protein fraction. In general, high concentrations of proteins were determined in NaOH extractants. On the other hand, low concentration of Cu, Fe, Mn and Zn were found in this fraction.