Elemental fingerprint profiling with multivariate data analysis to classify organic chocolate samples

Abstract

Chocolate is an appreciated food derived from cacao fruit. The flavonoids and minerals present in the chocolate have benefits to health, and some specific minerals are known to be toxic. Because of differences in their production systems, organic chocolate has a distinguishable pattern in mineral concentrations than conventional chocolate. Aiming for authenticity and study of the toxic elements in organic chocolate, we present in this work a simple method to classify organic chocolate samples based on elemental fingerprint profiling and multivariate data analysis. Thirty-eight elements (toxic and essential) were determined in 36 chocolate samples (organic and conventional) by using inductively coupled plasma mass spectrometry to establish reference ranges and to identify differences in patterns of elements in both type of samples.Our results showed that Al, Zn, Mn, Cu, and Ba are the most present components for both types of chocolate, and higher concentrations of essential elements Fe, Zn, and Mg are found in conventional type, opposing the idea that organic food is rich in essential elements. Principal component analysis and linear discriminant analysis were used for multivariate data analysis, and sample differentiation was possible with 83% accuracy.

Are the elemental fingerprints of organic and conventional food different? ED-XRF as screening technique

“…The largest difference was observed in the Fe content that was twice as high in conventional chocolates as in organic samples. The elemental composition of 36 chocolate samples characterised by ICP-MS, including 38 elements, has been previously used to classify organic chocolate by Junior et al ( Junior et al, 2018 ), who found higher concentrations of Fe, Zn and Mg in the conventional than in the organic chocolate.…”

“…The approaches used so far for authentication purposes can be divided in targeted and untargeted analysis. Targeted analysis addresses the determination of specific substances in food and are mostly represented by analysis of stable isotopes by Isotope Ratio Mass Spectrometry (IRMS) ( Liu et al, 2020 ), by multi-elemental analysis frequently carried out with ICP-based methods ( Junior et al, 2018 ) and by chromatographic methods for the determination of metabolites ( Eibler et al, 2018 ), or by combination of several of them. Untargeted analysis aims at analysing, in a holistic approach, all substances, some known and some unknown, in a certain sample.…”

“…Elemental analysis has been used alone or in combination with other approaches to discriminate organic from conventional food in a range of food commodities such as, rice ( Liu et al, 2020 ), cane sugar ( Barbosa et al, 2015 ), eggs ( Giannenas et al, 2009 ) and chocolate ( Junior et al, 2018 ). It is not our purpose to make a thorough review of all works published in this field, since in depth reviews on the use of elemental profiles to classify organic food can be found elsewhere (Laursen, K.H., Schjoerring, J.K., Kelly, S.D.…”

“…Studies published so far focused mostly on one or two food commodities cultivated in a specific geographical zone, belonging to one single botanical variety and if possible cultivated by one single producer, to avoid the variability introduced by sources other than the organic/conventional nature of the product ( Liu et al, 2020 ; Junior et al, 2018 ; Mazzei and Piccolo, 2018 ; Barbosa et al, 2016 ). In other works commercially available samples purchased at retailers were used to reflect the situation of the market ( Liu et al, 2018 ; Consonni et al, 2018 ; Eibler et al, 2018 ).…”

The elemental composition of chocolates is related to cacao content and origin: A multi-element fingerprinting analysis of single origin chocolates

“…chocolate. Junior et al (2018) used DA based on elemental composition to differentiate between organic and conventional chocolates and Bertoldi et al (2016) used 13 chocolates as a validation set to test the efficiency of their DA model for the classification of cacao beans by geographical origin.…”