1 Introduction  
1.1 Challenges of the Task  
1.2 Ripeness Standards  
1.3 Economical Impact of Fruit Ripeness Classification  
1.4 Predicting Fruit Ripeness  
1.5 Contributions and Structure of the Article  

2 Preliminaries  
2.1 Problem Statement  
2.2 Biology of Fruit Ripening  

3 Fruit Feature Representations  
3.1 Colour  
3.2 Volatiles  
3.3 Visible and Infrared Spectroscopy  
3.4 Fluorescence  
3.5 Spectral Imaging  

4 Data Preprocessing  

5 Approaches to Classification  
5.1 Statistical- and Machine-Learning-based  
5.2 Deep-Learning-based  

6 Prediction of Optimal Harvest Time  

7 Perspectives  

8 Conclusions