Artificial Neural Networks and Near Infrared Spectroscopy - A case study on protein content in whole wheat grainThe authors explain why the IFT calibrations are so robust for wheat. This is a case where more than 40000 samples are used with all the variability we can imagine for this type of product.
You can see the videos:
How Deep Neural Networks work?
What do Neural Networks learn?
for a better understanding of how ANN works.