Here's what Messy Jessie had to say about this scene when it was first released in 2014:

"I get to slime the gorgeous Dede with lots of colourful goo! I use a pretty pink gunge, custard, treacle and lots more! Dede's breasts look perfect covered in all that mess! "

I am not sure Jessie is quite right. I can see gunge and possibly custard... but I am not seeing any treacle. Treacle or no, Dede looks amazing after her gunging, that's for certain.