There is an ‘older’ tutorial by Jonathan Williamson how to hand-paint an apple texture (he uses Photoshop, but you can also use Krita of course).: https://www.youtube.com/watch?v=SXT0Dhr5VPc
Here is a procedural apple material:
http://www.blenderinsight.com/en-hemsides-sektion/joakim-tornhill-rendered-apples/
it has a link to the .blend file. Made for 2.79, but still working in 2.8+ if you adjust the Voronoi a bit. If you don’t want to use it, you still might be able to get an idea of how to make a material like that.
Didn’t I mention already that both nature and food are actually quite hard in CG?
