Can Muslims safely consider all vegetarian products as Halal?
If not then what are the things that are required to be looked at carefully before purchasing such products?
No, all vegetarian products need not be halal.
For example, Vanilla in liquid form may contain alcohol. It is vegetarian but not halal.
A food/drink being vegetarian eliminates the extra preclusions when consuming meat and animal products (Qur'an 2:173, 5:3, 6:121, 6:145). A food/drink being vegetarian makes is much easier for it to be halal, although there's some exceptions:
Vanilla extract ordinarily contains 35% alcohol, which should be considered haram to drink (or own) even if only in small amounts: "The Prophet [SAW] forbade a small amount of whatever intoxicates in large amounts." [grade: hasan] (sunnah.com). However, vanilla itself is ordinarily okay; see Islam Q&A.
Some brands of soy sauce contain sufficient alcohol to render it haram.
Kikkoman Soy Sauces contain greater than 2% alcohol by volume. -- FAQs About Sauces and Mixes
I wrote about alcohol-containing condiments in this answer.
Pig milk is vegetarian.
Vegetarian food might also be cooked using the same equipment that is used to cook pork, etc., which would render them haram.
Also, there's some ingredients which a less-strict vegetarian may not pay much attention to (possibly for practical reasons):
No, not all vegetarian products are Halal. Some vegetarian products have alcohol, and alcohol itself is mostly vegetarian in nature. It can be made out of grapes, apples etc etc. In Islam it is Haram to consume alcohol:
يَـٰٓأَيُّہَا ٱلَّذِينَ ءَامَنُوٓاْ إِنَّمَا ٱلۡخَمۡرُ وَٱلۡمَيۡسِرُ وَٱلۡأَنصَابُ وَٱلۡأَزۡلَـٰمُ رِجۡسٌ۬ مِّنۡ عَمَلِ ٱلشَّيۡطَـٰنِ فَٱجۡتَنِبُوهُ لَعَلَّكُمۡ تُفۡلِحُونَ (٩٠)
O ye who believe! Intoxicants and gambling, (dedication of) stones, and (divination by) arrows, are an abomination― of Satan's handiwork: eschew such (abomination), that ye may prosper. (90)
Surah Al Ma'idah Ayah 90
You must try to avoid all Haram things in vegetarian products, the only thing I can think of that would be in the products is Alcohol. There might be other things, but I do not have the knowledge of it. Examples of products that sometimes have alcohol is vanilla extract and soy sauce.
I believe the question is about vegetarian food which is halal or not.
Currently halal diet has been removed from the menu of most institutions who offer vegetarian diet as a substitute/alternative. But the fact stands, that not all vegetarian diet is halal.
Even most sweets contain alcohol. Chewy sweets contain gelatine and are not all halal based as the source is suspect as gelatine is animal based. One big sweet company answered my query as ff; "I can confirm that most of our products contain pig gelatine and are therefore unsuitable for a halal diet. We use ethanol and ethyl alcohol in our production process as carrier for the flavouring, but this constitutes less than 0.05% of the recipe and is flashed off during the process and not present in the final product.
I believe that even the "flashing" of the alcohol does not make this sweet halal. Any amount of alcohol is haram. But I would give exceptions on natural occurring molasses in food like corn dough which is actually not alcohol? Please correct me if I am wrong.
Examples Examples of products that sometimes have alcohol is vanilla extract and soy sauce.
Chips is "vegetarian" food but not halal if fried with lard. Lard is made from animal fat.
Surprisingly Muslims are unduly asked to sacrifice from eating any meat and are not offered other proper alternatives such as fish (which are all halal as they are not required to be slaughtered).
I was shocked to know that even some cheese are also not halal as in some of them animal fat is added.
Can someone give me some more from the list of "vegetarian" food that is not halal, please.
Chips fried in lard, and sweets with gelatine in them, are not vegetarian either. Vegetarians do not eat products from dead animals, so they would be unacceptable in both vegetarian and Halal diets. Vanilla extract and soy sauce are acceptable for a vegetarian diet though, regardless of alcohol content, so that would be a conflict I hadn't thought of before.
Look out for rennet in cheese. Non vegetarian cheese uses rennet made from newborn calf stomachs. Vegetarian cheeses should be Halal.
Kefir, the 'Drink of the Prophet' is halal,( according to The Halal Foundation) yet as a fermented product of milk using kefir grains ' the grains of the prophet' contains a small amount of alcohol, typically less than 1%. This seems to point to a more 'common sense' interpretation of what can cause intoxication and what can not.