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

Juliana Naozuka,Pedro V. Oliveira

doi:10.1590/s0103-50532007000800015

Abstract

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.

Highlights

Foods are one of the main sources of metals for human body
Proteins were directly extracted from the defatted cake using water, NaCl, ethanol and NaOH solutions for albumins, globulins, prolamins and glutelins extraction, respectively
It can be seen that, protein concentrations found in Brazil-nut are higher than those observed for cupuassu seed and coconut pulp

Summary

Introduction

Foods are one of the main sources of metals for human body. Most of the metal ions present in foods are bound to specific proteins or enzymes and exert their effects as active or structural centers, command process such as catalysts, substrate binding and activation, transportation and storage.[1,2] In this way, the knowledge of the foods compositional, nutritional and functional properties is fundamental for defining their quality. Efforts have been made to understand the interactions of metals with proteins and enzymes present in foods. Terms like metal-binding proteins and metalloproteins are more and more frequent in the food chemistry literature. It has been estimated that around 40% of all proteins and enzymes contain metal ions in their structures

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