Are Mangrove Jack's Yeasts Gluten & GMO Free? Yes - all Mangrove Jack's Yeasts are Gluten and GMO free.They only consist of yeast and emsulfier E491 and some strains have extra nutrients, but they are completely gluten and GMO free. Related articles What is Hysteresis? Why does my fermenter go above/below my target temperature before the cooling/heating is triggered? Why is there a black sludge on the inside of my GF30? What is it and how do I clean it? What do I do if the final gravity (FG) is higher than expected? How long can I leave my beer in the fermenter after the SG reading is stable? How often should I dump dead yeast and dry hops?