Cooking effects on iron and proteins content of beans (Phaseolus Vulgaris L.) by GF AAS and MALDI-TOF MS

Juliana Naozuka,Pedro V Oliveira

doi:10.1590/s0103-50532012000100022

Abstract

The effects of domestic cooking on proteins, organic compounds and Fe distribution in beans (Phaseolus vulgaris L.) were investigated. Sequential extraction with 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. Iron determination by graphite furnace atomic absorption spectrometry (GF AAS), proteins by Bradford method and organic compounds by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were carried out in this work. High concentration of albumins, globulins and glutelins were found in raw beans, while in the cooked beans, albumins and glutelins are main proteins types. The MALDI-TOF MS spectra of raw and cooked beans revealed that the domestic cooking altered the molecular weight of the organic compounds, since that in the cooked beans were found compounds between 2 and 3.5 kDa, which were not presented in the raw beans. Besides this, in cooked beans were also observed the presence of four compounds of high molecular weight (12-16 kDa), being that in the raw grains there is only one (ca. 15.2 kDa). In raw grains is possible to observe that Fe is mainly associated to albumins, globulins and glutelins. For cooked grains, Fe is associated to albumins and globulins.

Highlights

Beans (Phaseolus vulgaris L.) are a typical culture of tropical and subtropical weather
The results are shown in the Table 2. It is well discussed in the literature[12,13] that the extractants water, NaCl, ethanol and NaOH promoted the separation of different groups of proteins: albumins, globulins, prolamins and glutelins, respectively.[12,13]
The total protein concentration obtained by the masses sum of all extracts revealed that cooking promoted a sensible decrease in the protein content, mainly in the globulins fraction, when compared to the uncooked beans

Summary

Introduction

Beans (Phaseolus vulgaris L.) are a typical culture of tropical and subtropical weather. Brazil is the largest worldwide producer (2.2-2.5 million tons, in approximately 5 million hectares cultivated) and consumer Beans is one of the richest foods in proteins consumed by the Brazilian population.[1] Normally, countryside population is responsible for the high consumption of this food.[1,2] consumption of beans is declining, due to the changes in traditional dietary habits of Brazilian population.[2]. Beans are a good source of vitamins, minerals (K, Ca, Mg, P and Fe salts), proteins (20-25%) and complex

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Conclusion