Monitoring of fluorescence characteristic in tomato surface during over-ripening stage

After harvesting, the evaluation of tomato characteristics is essential to decide a correct postharvest handling process, maturity stages, and shelf-life prediction. Previous research shows that fluorescence imaging could be used to enhance the maturity level detection after the red stage. However, the correlation between external appearance and internal fluorescence change has not been studied well. In this research, tomato surface has been classified into two parts i.e. skin and flesh. The parts have been extracted, and the fluorescence characteristic has been monitored from red-stages to over-ripening. The fluorescence image changes are confirmed during the storages and correlated with the weight loss as a freshness index. The results show that the fluorescence characteristic of tomato skin and flesh is different. The highest fluorescence emission peak for excitation of 370 nm is 520 nm for the skin and 490 nm for the flesh. Both fluorescence intensity of skin and flesh changed during storage. Although both changes could affect the fluorescence images, confirming the previous result, the changes of the skin fluorescence are strong enough to be observed with an imaging method. Classification of fresh and spoilage tomato samples using weight loss and images were also conducted using a Partial Least Square-Discriminant Analysis (PLS-DA) model with 92% accuracy. These results demonstrate the potential of fluorescence imaging to monitor tomato freshness during storage.