TY  - JOUR
A1  - Zude, Manuela
A1  - Pflanz, Michael
A1  - Spinelli, Lorenzo
A1  - Dosche, Carsten
A1  - Torricelli, Alessandro
T1  - Non-destructive analysis of anthocyanins in cherries by means of Lambert-Beer and multivariate regression based on spectroscopy and scatter correction using time-resolved analysis
JF  - Journal of food engineering
N2  - In high-value sweet cherry (Prunus avium), the red coloration - determined by the anthocyanins content - is correlated with the fruit ripeness stage and market value. Non-destructive spectroscopy has been introduced in practice and may be utilized as a tool to assess the fruit pigments in the supply chain processes. From the fruit spectrum in the visible (Vis) wavelength range, the pigment contents are analyzed separately at their specific absorbance wavelengths.
 A drawback of the method is the need for re-calibration due to varying optical properties of the fruit tissue. In order to correct for the scattering differences, most often the spectral intensity in the visible spectrum is normalized by wavelengths in the near infrared (NIR) range, or pre-processing methods are applied in multivariate calibrations.
 In the present study, the influence of the fruit scattering properties on the Vis/NIR fruit spectrum were corrected by the effective pathlength in the fruit tissue obtained from time-resolved readings of the distribution of time-of-flight (DTOF). Pigment analysis was carried out according to Lambert-Beer law, considering fruit spectral intensities, effective pathlength, and refractive index. Results were compared to commonly applied linear color and multivariate partial least squares (PLS) regression analysis. The approaches were validated on fruits at different ripeness stages, providing variation in the scattering coefficient and refractive index exceeding the calibration sample set.
 In the validation, the measuring uncertainty of non-destructively analyzing fruits with Vis/NIR spectra by means of PLS or Lambert-Beer in comparison with combined application of Vis/NIR spectroscopy and DTOF measurements showed a dramatic bias reduction as well as enhanced coefficients of determination when using both, the spectral intensities and apparent information on the scattering influence by means of DTOF readings. Corrections for the refractive index did not render improved results.
KW  - Cherry
KW  - DTOF
KW  - Effective pathlength
KW  - Fruit maturity
KW  - Lambert-Beer
KW  - NIR
KW  - Non-invasive
KW  - Pigments
KW  - PLS
KW  - Ripeness
KW  - Sensor fusion
KW  - Spectroscopy
KW  - Time-resolved spectroscopy
KW  - TIRF
KW  - Vis
KW  - Scattering
Y1  - 2011
U6  - https://doi.org/10.1016/j.jfoodeng.2010.09.021
SN  - 0260-8774
VL  - 103
IS  - 1
SP  - 68
EP  - 75
PB  - Elsevier
CY  - Oxford
ER  -