Question:
What is the ruling of E numbers and what does it mean by suitable for vegetarians?
Answer:
In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
An E number is a reference number given to food additives that have passed safety tests and have been approved for use throughout the European Union (EU).
Common food additives include:
Antioxidants 
These help prolong the shelf life of many foods, including foods prepared with fats or oils (such as meat pies or mayonnaise), bakery products, soup mixes and sauces.
Colours 
These are used to make food more attractive. They can be natural in origin such as curcumin (E100), a yellow extract of turmeric roots, or artificial such as tartrazine (E102).
Emulsifiers, stabilisers, gelling agents and thickeners 
These prevent foods from separating and give food body and texture. For example, pectin (E440) is the most common gelling agent and is used in jam.
Flavour enhancers 
These bring out the flavour in foods without adding their own flavour. For example, monosodium glutamate (E621) or MSG is used in processed foods such as soups and sauces.
Preservatives 
These keep food safe for longer. For example, nitrite and nitrate (E249 to E252) are used in bacon, ham, corned beef and other cured meats to stop bacteria from growing.
Sweeteners are used with or instead of sugar to make food taste sweet. Examples include aspartame (E951), saccharin (E954) and sorbitol (E420).
The wide spectrum of E numbers is visible.  Therefore, it is impossible to issue one ruling with regards to E numbers.  Each E number will have a different ruling based upon its origin and source.
If a food is labelled suitable for vegetarians, this usually means that the food doesn’t contain any meat or animal-derived additives such as gelatine (a gelling agent derived from animal ligaments, skins, tendons, bones etc.)[1]
And Allah Ta’ālā Knows Best
Mufti Faraz al-Mahmudi,
Darul Iftaa
Dublin, Ireland
www.darulfiqh.com