Evaluating the shelf life of strawberries using a portable Vis-NIR spectrophotometer and a Reflectance Quality Index (RQI)

Abstract

This study aimed to develop a postharvest quality index for strawberry (Fragaria ananassa Duch.) based on Vis-NIR reflectance, using a portable handset spectrometer to assess fruit quality and establish maximum shelf life. Fresh strawberries were stored at different temperatures (5, 15, 25 and 35 °C) and at 60 % relative humidity for up to 15 days. Various quality parameters were evaluated, including colour, firmness, weight loss, appearance, and microbial quality, every three days during storage. Kinetic models were used to describe the changes in weight loss, appearance, colour, and firmness of strawberries during storage under different temperatures. Vis-NIR spectroscopy was employed to establish a Reflectance Quality Index (RQI) for determining fruit quality during storage. This index helped to reduce the high number of wavelengths to a lower set of representative independent variables. Calibration and prediction models were created using the partial least squares (PLS) regression method, incorporating cross-validation, to predict quality indicators of strawberries. These models were developed for predicting appearance, weight loss, L*, a*, b* colour parameters, and firmness. A very good fit was obtained (R2 = 0.95), demonstrating the feasibility of both the RQI and PLS for evaluating strawberry quality. This study presents a novel approach for assessing the shelf life of strawberries based on storage time and temperature using a portable spectrophotometer. This method can be a valuable tool for the food industry to ensure optimal fruit quality and minimize food losses.