gel substance to keep food moist? I've seen this in mostly chain supermarket and Costco. 

When they make sushi, they would brush this clear gel like substance on the sushi maki roll either to keep it moist or fresh for long period of time. Anyone know what that stuff is call?
This is likely to be guar or xanthan gum  

http://www.uwec.edu/Dining/locations/upload/SushiDO_Ingredients.pdf 

(Look at one of the items like a Philadelphia roll). 

Not very appetising but does keep in 'kind of' fresh