Spectrophotometric versus NIR-MIR assessments of cowpea pods for discriminating the impact of freezing.
BACKGROUND
Freezing represents an important storage method for vegetal foodstuffs, such as cowpea pods, and thus the impact of this process on the chemical composition of these matrices arises as a prominent issue. In this sense, the phytochemical contents in frozen cowpea pods (i.e. at 6 and 9 months) have been compared with fresh cowpea pods material, with the samples being concomitantly assessed by Fourier-transform infrared spectroscopy (FTIR), both mid-infrared (MIR) and near infrared (NIR), aiming to evaluate the potential of these techniques as a rapid tool for the traceability of these matrices.


RESULTS
A decrease in phytochemical contents during freezing was observed, allowing the classification of samples according to the freezing period based on such variations. Also, MIR and NIR allowed discrimination of samples: the use of the first derivative demonstrated a better performance for this purpose, whereas the use of the normalized spectra gave the best correlations between the spectra and specific contents. In both cases, NIR displayed the best performance.


CONCLUSIONS
Freezing of cowpea pods leads to a decrease of phytochemical contents, which can be monitored by FTIR spectroscopy, both within the MIR and NIR ranges, whereas the use of this technique, in tandem with chemometrics, constitutes a suitable methodology for the traceability of these matrices. © 2017 Society of Chemical Industry.
UTAD-CITAB - Centre for the Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes and Alto, Vila Real, Portugal.
Nelson
N
Machado
UTAD-CITAB - Centre for the Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes and Alto, Vila Real, Portugal.
Raúl
R
Domínguez-Perles
UTAD-CITAB - Centre for the Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes and Alto, Vila Real, Portugal.
Ana
A
Ramos
UTAD-CITAB - Centre for the Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes and Alto, Vila Real, Portugal.
Eduardo As
EA
Rosa
UTAD-CITAB - Centre for the Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes and Alto, Vila Real, Portugal.
Ana Irna
AI
Barros
D005519:Food Preservation; D061353:Food Storage; D005615:Freezing; D064209:Phytochemicals / Q000032:analysis; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D000070658:Vigna / Q000737:chemistry*
D064209:Phytochemicals
FTIR-spectroscopy; cowpea; immature pods; multivariate analysis; phenolic composition; radical scavenging capacity