Analysis of Moisture Content in Beetroot using Fourier Transform Infrared Spectroscopy and by Principal Component Analysis

Abstract

The moisture content of beetroot varies during long-term cold storage. In this work, we propose a strategy to identify the moisture content and age of beetroot using principal component analysis coupled Fourier transform infrared spectroscopy (FTIR). Frequent FTIR measurements were recorded directly from the beetroot sample surface over a period of 34 days for analysing its moisture content employing attenuated total reflectance in the spectral ranges of 2614-4000 and 1465-1853 cm^-1 with a spectral resolution of 8 cm^-1. In order to estimate the transmittance peak height (T _p ) and area under the transmittance curve [Formula: see text] over the spectral ranges of 2614-4000 and 1465-1853 cm^-1, Gaussian curve fitting algorithm was performed on FTIR data. Principal component and nonlinear regression analyses were utilized for FTIR data analysis. Score plot over the ranges of 2614-4000 and 1465-1853 cm^-1 allowed beetroot quality discrimination. Beetroot quality predictive models were developed by employing biphasic dose response function. Validation experiment results confirmed that the accuracy of the beetroot quality predictive model reached 97.5%. This research work proves that FTIR spectroscopy in combination with principal component analysis and beetroot quality predictive models could serve as an effective tool for discriminating moisture content in fresh, half and completely spoiled stages of beetroot samples and for providing status alerts.

Figure 1

(a) FTIR spectra of fresh and spoiled beetroot samples recorded in the spectral range of 400–4000 cm⁻¹ and FTIR spectra of beetroot samples recorded for a period of 34 days in the spectral ranges of (b) 2614–4000 cm⁻¹ and (c) 1465–1853 cm⁻¹.

Figure 2

Gaussian fitted FTIR spectra of beetroot samples recorded for a period of 34 days in the spectral ranges of (a) 2614–4000 cm⁻¹ and (b) 1465–1853 cm⁻¹ and (c) principal component analysis score plot for beetroot quality classification.

Figure 3

The plots of T_p vs days and ${\int }_{{\overline{\nu }}_i}^{{\overline{\nu }}_f}{T}_{p}d\overline{\nu }$ vs days measured in the spectral ranges of 1465–1853 cm⁻¹ (a and b) and 2614–4000 cm⁻¹ (c and d) for the determination of age of beetroot using biphasic dose response model (standard error ≤ 0.01).

Figure 4

(a) FTIR spectra of beetroot samples 1 and 2 measured in the spectral range of 600–4000 cm⁻¹, (b) Gauss fitted FTIR spectra of beetroot samples 1 and 2 recorded in the spectral range of 2614–4000 cm⁻¹, (c) principal component analysis score plot for beetroot quality classification and determination of age of beetroot using biphasic dose response model: (d) T_p vs days and (e) ${\int }_{{\overline{\nu }}_i}^{{\overline{\nu }}_f}{T}_{p}d\overline{\nu }$ vs days.