Abstract
A simple and fast, non-digestion treatment, and fully validated preparation procedures of dialyzable and non-dialyzable fractions of brews of ground (GCs) and instant (ICs) coffees prior to their elemental analysis (Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Sr, and Zn) by flame atomic absorption spectrometry (F AAS) and inductively coupled plasma optical emission spectrometry (ICP OES) was developed. Three different procedures: wet digestions (P1), direct analysis (P2), and acidification with HNO3 (P3) were tested. Among tested procedures, the direct analysis (P2) gave the most satisfactory results, i.e., precision from 0.54% (Fe) to 5.9% (Cu), recoveries ranging between 98.0% (Sr) and 104% (Al), detection limits within 0.095 (Ba)–1.8 (Ni) μg L−1, and quantification limits from 0.32 (Ba) to 6.0 (Ni) μg L−1. The chosen procedure was applied to determine bioaccessibility of 11 elements in GCs and ICs coffees using in vitro gastrointestinal digestion. Average contributions of the bioaccessible fraction (%) of elements in brews were as follows: Al (19.0, 23.0), Ba (42.8, 48.4), Ca (35.0, 38.9), Cr (< LOD, 31.1), Cu (15.0, 14.3), Fe (5.08, 2.81), Mg (32.2, 37.9), Mn (28.1, 29.1), Ni (40.9, 60.0), Sr (43.2, 45.6), and Zn (11.5, 9.57) for GCs and ICs coffees, respectively. Generally, bioaccessibility of most elements, i.e., Al, Ba, Ca, Cu, Mg, Mn, Ni, and Sr in brews of GCs was lower than this determined in ICs and varied from 4% (Mn) to 47% (Ni). In contrast, higher contributions of the bioaccessible fraction of Fe and Zn were assessed for GCs brews (47% and 17%, respectively), than these evaluated in ICs brews. Additionally, results on total concentrations of elements in brews of GCs and ICs and concentrations of elements in the dialyzable fraction separated from these brews were applicable to differentiate and classify all analyzed coffees by principal component analysis (PCA).
Highlights
Today, coffee brewed from ground roasted coffee (GC) beans or prepared directly from soluble coffee (IC) powders is one of the most consumed beverage in the world
Intestinal digestion is imitated using a mixture of pancreatin (0.015–3.04%) and bile salts (0.15–2.8%) adjusted to pH~7 by addition of a Na2CO3 solution (0.1 or 1.0 mol L−1) (Hur et al 2011; Intawongse and Dean 2006)
Elements released to soluble or dialyzable fractions are determined by flame atomic absorption spectrometry (F AAS), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP-MS)
Summary
Coffee brewed from ground roasted coffee (GC) beans or prepared directly from soluble (instant) coffee (IC) powders is one of the most consumed beverage in the world. Knowledge about total concentrations of elements in food and beverages is usually used to judge their nutritional value and degrees of coverage of their daily recommended dietary intakes (RDIs). Before spectrochemical analysis, resulting sample solutions can be initially prepared with the aid of open-vessel or closedvessel wet digestions (do Nascimento da Silva et al 2015; García-Sartal et al 2011, 2013; Peixoto et al 2013; Souza et al 2018) or analyzed directly, i.e., without any pre-treatment (de Lima et al 2014; Dominguez-Gonzalez et al 2010; do Nascimento da Silva et al 2017; Erdemir 2018; Khouzam et al 2011; Lamsal and Beauchemin 2015; Menezes et al 2018; Pereira et al 2016; Pereira Junior et al 2018)
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