Collaborative representation of convolutional neural network features to detect artificial ripening of banana using multispectral imaging

With the increasing demand for fruits in the consumer market and to fulfill the needs of consumers, fruits are deliberately resorted to ripen artificially using industrial-grade Calcium Carbide (CaC2) which has carcinogenic properties. The preferences to employ imaging sensing technology across the electromagnetic spectrum have gained noteworthy attention in recent times. This work presents the study to distinguish between natural and artificially ripened bananas using a multispectral imaging approach. Specifically, we carry out the analysis using multispectral images collected for natural and artificially ripened bananas in eight narrow spectrum bands spanning from visible (VIS) to near-infrared (NIR) wavelength. Further, to present the contribution of each individual spectral band, we propose a scheme that extracts the relevant features from "convolution 5 (conv5)" and "fully connected 6 (fc6)" layers of convolutional neural network (CNN) based on AlexNet architecture and processes these features independently with collaborative representation classifier (CRC) in a robust manner. Essentially, we demonstrate the experimental classification accuracy based on multispectral images comprised of 5760 sample images using 10-fold cross-validation. Based on the proposed scheme, the highest average classification accuracy of about 88.82 +/- 1.65% is obtained using our proposed approach presenting the significance of our work. Practical applications The practical application of our proposed approach is to distinguish between natural and artificially ripened banana fruits in a market chain. Further, the approach is non-invasive and non-destructive based on multispectral imaging which has the potential to carry out real-time quality analysis of bananas, especially to detect adulteration.