Uses of mid-infrared spectroscopy and chemometric models for differentiating between dried cocoa bean varieties

Collazos-Escobar, Gentil A.; Barrios-Rodriguez, Yeison F.; Bahamón-Monje, Andrés F.; Gutiérrez-Guzmán, Nelson

doi:10.1590/1807-1929/agriambi.v27n10p803-810

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Articles • Rev. bras. eng. agríc. ambient. 27 (10) • Oct 2023 • https://doi.org/10.1590/1807-1929/agriambi.v27n10p803-810 copy

Uses of mid-infrared spectroscopy and chemometric models for differentiating between dried cocoa bean varieties¹ 1 Research developed at Universidad Surcolombiana/South Colombian Coffee Research Center/Department of Agricultural Engineering, Neiva, Colombia

Utilização de espectroscopia de infravermelho médio e modelos quimiométricos para discriminação de variedades de cacau seco

Authorship SCIMAGO INSTITUTIONS RANKINGS

HIGHLIGHTS:

The ATR-FTIR technique discriminates between cocoa genotypes by chemometric methods.

The LDA and PLS-DA chemometric models achieve high reliability in the discrimination of food matrices.

It will be possible to improve the processes of dry cocoa bean classification in the industry.

ABSTRACT

Generally, the taxonomic classification of cocoa beans is based on the theobromine/caffeine ratio determined using high-performance liquid chromatography (HPLC). However, this technique involves laborious and time-consuming calculations. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy is a valuable, effective, and rapid tool for analyzing the chemical composition of food products. The objective of this study was to examine the potential of ATR-FTIR combined with chemometric tools such as principal component analysis (PCA), linear discriminant analysis (LDA), and partial least squares regression-discriminant analysis (PLS-DA) to discriminate between the Trinitario and Forastero dry bean cocoa varieties defined by theobromine and caffeine measurements via HPLC. The cocoa varieties were evaluated using HPLC analysis of 36 dry cocoa bean samples to determine the theobromine/caffeine ratio. Moreover, ATR-FTIR spectra were analyzed in the mid-infrared (MIR) region, and signals associated with theobromine and caffeine were identified and analyzed using the LDA and PLS-DA models. The LDA and PLS-DA models allowed the satisfactory differentiation between cocoa varieties, providing overall prediction capacity values of 98.2 ± 1.8% and 96.1 ± 2.4%, respectively. The results show the potential of ATR-FTIR spectroscopy for the reliable, fast, and easy differentiation of dried cocoa beans.

Key words:
Theobroma cacao; ATR-FTIR; multivariate statistical tools; theobromine; caffeine

Municipality	Latitude	Longitude	Altitude (masl)	Municipality	Latitude	Longitude	Altitude (masl)
Municipality	Latitude	Longitude	Altitude (masl)	Municipality	Latitude	Longitude	Altitude (masl)	Colombia	3° 24’ 35.73’’ N	74° 48’ 38.94’’ W	736	Algeciras	2° 43’ 14.1’’ N	75° 15’ 51.6’’ W	863
Colombia	3° 23’ 9.74’’ N	74° 49’ 18.31’’ W	750	Algeciras	2° 32’ 48.8’’ N	75° 18’ 17.1’’ W	1,020
Tello	2° 59’ 49’’ N	75° 4’ 20.5’’ W	1,222	Algeciras	2° 32’ 50.8’’ N	75° 17’ 19.3’’ W	1,101
Tello	2° 59’ 56’’ N	75° 3’ 52.2’’ W	1,211	Rivera	2° 49’ 19’’ N	75° 14’ 2.2’’ W	660
Tello	3° 1’ 7.9’’ N	75° 3’ 39.6’’ W	1,172	Rivera	2° 44’ 50.6’’ N	75° 14’ 58.9’’ W	874
Palermo	2° 50’ 41.1’’ N	75° 33’ 35.9’’ W	1,106	Colombia	3° 21’ 32.54’’ N	74° 50’ 17.8’’ W	700
Palermo	2° 49’ 29.7’’ N	75° 33’ 58.7’’ W	1,185	Tello	3° 0’ 18.2’’ N	75° 3’ 49.6’’ W	1,297
Santa María	2° 57’ 23’’ N	75° 30’ 21.2’’ W	843	Tello	2° 59’ 55.4’’ N	75° 4’ 34.1’’ W	1,019
Santa María	2° 56’ 57’’ N	75° 33’ 34.3’’ W	1,197	Tello	2° 58’ 55’’ N	75° 4’ 9.2’’ W	984
Teruel	2° 48’ 10.1’’ N	75° 33’ 17.1’’ W	1,060	Tello	2° 59’ 8.6’’ N	75° 4’ 16’’ W	1,025
Teruel	2° 46’ 53.9’’ N	75° 31’ 32.4’’ W	815	Palermo	2° 51’ 32’’ N	75° 30’ 56.9’’ W	769
Íquira	2° 39’ 20.2’’ N	75° 36’ 32.8’’ W	834	Palermo	2° 49’ 19.46’’ N	75° 33’ 52.62’’ W	1,200
Íquira	2° 39’ 11.2’’ N	75° 38’ 27.4’’ W	1,179	Santa María	2° 51’ 42.2’’ N	75° 33’ 36.2’’ W	834
Nátaga	2° 32’ 16.8’’ N	75° 49’ 30.6’’ W	1,300	Teruel	2° 46’ 57.2’’ N	75° 32’ 34.1’’ W	845
Nátaga	2° 32’ 32.58’’ N	75° 49’ 50.5’’ W	1,190	Teruel	2° 42’ 22’’ N	75° 35’ 55.7’’ W	885
Nátaga	2° 32’ 19.1’’ N	75° 49’ 9.2’’ W	1,345	Íquira	2° 38’ 17.4’’ N	75° 39’ 14.5’’ W	960
Gigante	2° 25’ 17.13’’ N	75° 25’ 17.13’’ W	943	Gigante	2° 23’ 30.95’’ N	75° 31’ 47.37’’ W	916
Gigante	2° 21’ 40.94’’ N	75° 31’ 46.23’’ W	1,040	Campoalegre	2° 36’ 7.3’’ N	75° 20’ 7.9’’ W	424

Theobromine/Caffeine	Variety	Theobromine/Caffeine	Variety
8.630 ± 0.241	Trinitario	8.061 ± 0.717	Trinitario
8.263 ± 0.372	Trinitario	6.335 ± 0.482	Trinitario
8.900 ± 0.392	Trinitario	4.750 ± 0.257	Trinitario
8.012 ± 0.102	Trinitario	8.702 ± 1.121	Trinitario
7.178 ± 0.523	Trinitario	8.066 ± 2.115	Trinitario
8.362 ± 0.343	Trinitario	9.107 ± 0.648	Forastero
8.733 ± 0.808	Trinitario	10.473 ± 0.894	Forastero
6.893 ± 0.189	Trinitario	11.128 ± 0.297	Forastero
7.396 ± 0.515	Trinitario	14.429 ± 0.776	Forastero
5.988 ± 0.164	Trinitario	9.284 ± 0.465	Forastero
5.409 ± 0.908	Trinitario	10.026 ± 0.564	Forastero
6.624 ± 0.327	Trinitario	9.965 ± 0.634	Forastero
4.769 ± 0.118	Trinitario	12.126 ± 0.138	Forastero
6.860 ± 0.276	Trinitario	10.239 ± 0.397	Forastero
5.783 ± 0.247	Trinitario	9.301 ± 1.192	Forastero
7.688 ± 0.817	Trinitario	9.601 ± 0.310	Forastero
7.601 ± 0.503	Trinitario	12.910 ± 2.262	Forastero
8.452 ± 0.872	Trinitario	14.035 ± 0.514	Forastero

Variety	Theobromine	Caffeine	Theobromine/Caffeine
Variety	(mg g^‒1)		Theobromine/Caffeine
Trinitario	20.3 ± 2.8a	2.9 ± 0.8a	7.3 ± 1.4a
Forastero	18.7 ± 2.1b	1.7 ± 0.3b	10.97 ± 1.92b

Linear discriminant analysis (LDA)
Calibration set (n = 27)
	Trinitario	Forastero	Overall accuracy (%)
Predicted Trinitario	17 ± 1	0	98.2 ± 1.8
Predicted Forastero	0	10 ± 1
Sensitivity	0.98 ± 0.02
Specificity	0.99 ± 0.01
Precision	0.99 ± 4.76 × 10–3
Recall	0.98 ± 0.02
F-Score	0.99 ± 0.01
Validation set (n = 9)
	Trinitario	Forastero	Overall accuracy (%)
Predicted Trinitario	5 ± 1	0 ± 1	92.3 ± 7.7a
Predicted Forastero	0 ± 1	3 ± 1
Sensitivity	0.94 ± 0.1a
Specificity	0.91 ± 0.2a
Precision	0.95 ± 0.1a
Recall	0.94 ± 0.1a
F-Score	0.94 ± 0.07a
Partial least square regression-discriminant analysis (PLS-DA)
Calibration set (n = 27)
	Trinitario	Forastero	Overall accuracy (%)
Predicted Trinitario	17 ± 1	0	96.9 ± 1.7
Predicted Forastero	1	9 ± 1
Sensitivity	0.99 ± 0.01
Specificity	0.92 ± 0.04
Precision	0.95 ± 0.02
Recall	0.99 ± 0.01
F-Score	0.98 ± 0.01
Validation set (n = 9)
	Trinitario	Forastero	Overall accuracy (%)
Predicted Trinitario	6 ± 1	0	96.1 ± 2.4b
Predicted Forastero	0	3 ± 1
Sensitivity	0.98 ± 0.06b
Specificity	0.93 ± 0.15a
Precision	0.96 ± 0.07a
Recall	0.98 ± 0.06b
F-Score	0.97 ± 0.05b

Unidade Acadêmica de Engenharia Agrícola Unidade Acadêmica de Engenharia Agrícola, UFCG, Av. Aprígio Veloso 882, Bodocongó, Bloco CM, 1º andar, CEP 58429-140, Campina Grande, PB, Brasil, Tel. +55 83 2101 1056 - Campina Grande - PB - Brazil
E-mail: revistagriambi@gmail.com

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[1] * Corresponding author - E-mail: gentilcollazosescobar09@gmail.com

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Uses of mid-infrared spectroscopy and chemometric models for differentiating between dried cocoa bean varieties1 1 Research developed at Universidad Surcolombiana/South Colombian Coffee Research Center/Department of Agricultural Engineering, Neiva, Colombia

Utilização de espectroscopia de infravermelho médio e modelos quimiométricos para discriminação de variedades de cacau seco

HIGHLIGHTS:

ABSTRACT

Uses of mid-infrared spectroscopy and chemometric models for differentiating between dried cocoa bean varieties¹ 1 Research developed at Universidad Surcolombiana/South Colombian Coffee Research Center/Department of Agricultural Engineering, Neiva, Colombia