Silica optical fibres were used to measure colour (mg anthocyanin/g fresh berry weight) in samples of red wine grape homogenates via optical Fibre Evanescent Field Absorbance (FEFA). Colour measurements from 126 samples of grape homogenate were compared against the standard industry spectrophotometric reference method that involves chemical extraction and subsequent optical absorption measurements of clarified samples at 520 nm. FEFA absorbance on homogenates at 520 nm (FEFA_520h) was correlated with the industry reference method measurements of colour (R² = 0.46, n = 126). Using a simple regression equation colour could be predicted with a standard error of cross-validation (SECV) of 0.21 mg/g, with a range of 0.6 to 2.2 mg anthocyanin/g and a standard deviation of 0.33 mg/g. With a Ratio of Performance Deviation (RPD) of 1.6, the technique when utilizing only a single detection wavelength, is not robust enough to apply in a diagnostic sense, however the results do demonstrate the potential of the FEFA method as a fast and low-cost assay of colour in homogenized samples.

Date Published: 4 March 2013
PDF: 6 pages
Proc. SPIE 8761, PIAGENG 2013: Image Processing and Photonics for Agricultural Engineering, 87610R (4 March 2013); doi: 10.1117/12.2019633

Published in SPIE Proceedings Vol. 8761:
PIAGENG 2013: Image Processing and Photonics for Agricultural Engineering
Honghua Tan, Editor(s)