Is WD-40 alright to use in freezers/places with food?
Replace the Fan. 

If you insist on lubricating - Olive Oil works nicely.

EDIT 5-8-2017

You could buy food safe lubricants but they also might have unwanted odors and only allow for incidental contact with food.

Olive Oil on the other hand has been known to be a very good lubricant for a long long time at least as far back as the 12th Century, probably longer than that.

The Below Excerpt was copied from this Web Site PDF document: 
"olive oil spreads easily and thoroughly over the rubbing surfaces. 
Unlike the drying oils, it does not gum, taking up to seven days 
to gain as little as 1.7 percent of its weight after exposure to the air. 
Most important, olive oil stands up extremely well under pressure because of its viscosity and oiliness. 
Not only can it surmount the thrusts of force-closure, but after the machine is set in motion it also maintains 
coefficients of friction between 0.07 and 0.08 whether it is running between surfaces of wood and metal, wood and wood, or metal and metal. 
Perhaps its only weakness is that it can become too acidic, especially if the olives are left to ferment too long before going to the press. 
This disadvantage was overcome by simply pressing the olives as soon as possible. 
Within Tuscany and its immediate vicinity, then, olive oil was known as an efficient lubricant that could endure great stress."