Identification of mushrooms subjected to freeze damage using hyperspectral imaging

Abstract

In this study, the potential use of hyperspectral imaging (HSI) for early detection of freeze damage in white button mushrooms was investigated. Hyperspectral images of mushroom samples were obtained using a pushbroom line-scanning HSI instrument in the wavelength range of 400 to 1000 nm. Reflectance spectra from each mushroom sample were obtained from various positions on the mushroom surface and pretreated using the Standard Normal Variate (SNV) transformation. Weight loss (WL) and Hunter L-value of mushroom samples were also measured over the storage period. At early stages of thawing, frozen samples were similar in appearance, WL and L-value to undamaged mushrooms, while substantial changes in WL and L-value were evident in freeze-damaged mushrooms after 24 h thawing. A procedure based on Principal Components Analysis and Linear Discriminant Analysis was developed for classification of both selected spectra and whole mushrooms into undamaged and freeze-damaged groups. Applying this procedure to an independent test set, 100% of whole undamaged mushrooms were correctly classified and 97.9% of freeze-damaged samples were correctly classified. Using this method, freeze-damaged mushrooms could be classified with high accuracy (>95% correct classification) after only 45 min thawing (at 23 ± 2 °C) at which time freeze–thaw damage was not visibly evident.