My mealies smell like candy :)

[Linds]

LOL... ok so my mealworm colonies all stink like caramel. It's a pleasant odour, but I have absolutely no idea what it is caused from? I have never had this problem before in the past, I've always used the same formula for substrate and foods, and I have also had moldy colonies in the past and it isn't the same smell that resulted from that. I'm pretty stumped. Although it can't possibly be the substrate since for years I never had this problem, I keep them in a subtrate of

pablum (the mixed fruit type)
rolled oats
quinoia
12 grain mix
rye flakes
spirulina
wheat germ
red bran
white bran
oat bran
fish food flakes

and feed them for water all sorts of fruits, veggies, and greens such as:

collards
spring greens
orange pepper
kiwi
pears
strawberries
dandelion
grapes
mandarin oranges
cucumber
(etc, etc.....)

I just want to be sure whatever is causing this odour will not be causing any harm as well