It appears from your description that you may be referring to what is called white core of tomatoes. This is believed to be linked to yellow shoulder disorder.  This disorder is rather complex and is related to proper nutrient availability at fruit set.  Other factors include temperature, soil and water pH and variety of tomato.  Take a look at the following links for more information:

http://www.hort.cornell.edu/expo/proceedings/2012/Greenhouse%20and%20High%20Tunnels/High%20Tunnels%20Bogash.pdf

https://ipm.missouri.edu/meg/2012/8/Hot-Weather-Tomato-Problems/

I hope this is helpful,