What it is and where it comes from
E491 joins sorbitol, a sugar alcohol made from plants, with stearic acid. The fatty acids can come from plant oils such as palm, soy, sunflower or rapeseed, or from animal fat, including pork fat. Most made today is from plants, but the label rarely says which.
Where you find it
Dried baking yeast, cakes, icing, whipped toppings, chocolate and some vitamins.
What to look for on the label
Look for a halal logo, a vegan label, or a note such as "of vegetable origin" next to the E-number. If the label says nothing, ask the maker: many companies answer by email within days. Packets of dried yeast often contain E491, so check those too.
This is a guide, not a fatwa. Recipes change, so check the label, look for halal certification, and ask your local imam where scholars differ.