Estimation of the prior storage period of lamb's lettuce based on visible/near infrared reflectance spectroscopy

Lamb's lettuce (Valeriarzella locusta L.) can be stored up to 28 days without being indistinguishable from fresh material by the human eye. However, due to the prior storage period the shelf life potential is limited and this leads to losses in distribution and a lower quality for the consumer. This work aims to develop a rapid and non-destructive methodology using visible/near infrared (Vis/NIR) reflectance spectroscopy to detect and quantify a prior storage period. Vis/NIR reflectance spectra were linked to the time in storage by partial least squares regression (PLS). Different variable selection techniques (interval PLS, Variable Importance in Projection scores, Genetic Algorithms PLS and Monte Carlo Uninformative Variable Elimination PIS) were combined to improve the accuracy and robustness of the prediction model, while decreasing the number of used wavelengths. The final model used only 10% of the original wavelengths, while the root mean squared error of cross validation decreased from 6.0 to 3.6 days. The final model was tested using 2 external test sets and had a maximum root mean square error of prediction of 3.7 days. Vis/NIR reflectance spectroscopy can be a valuable, rapid and non-destructive method for identifying and quantifying a prior storage period of lamb's lettuce. (C) 2015 Elsevier B.V. All rights reserved.