why do these kosher foods need a hechsher?

This question is not easily provided but mainly they require a hecksher because of the process they undergo, and the chemeicals that process is making them go thru.

{Some} chemicals have non-kosher animal bi-products and make potentialy kosher food products non-kosher which is obviously a reason to disqualify them as kosher, because the chemicals that have been processed alongside the food products means that they would be eaten by the jew and would constitute eating the forbidden foods and that will result in a breech in halacha and the Torah states we are to becareful in our observance towards his mitzvot.

Edit-----To know what chemicals may or may not be used you would need to read the ingredients and determine [by halacha] wether you can use this or that.

For instance your very first product [tomatoes] you mentioned does not require a hechsher if they are plucked from it's branch but if processed and placed in cans then it would require a hechsher because of the process it underwent.

Edit---Nay stated correctly it's not only about non-kosher food bi-products mixed in with chemicals that needs to be supervised but also wether your meats have been handled in dairy utensiles etc... or in a dairy prodution line or vise versa if a dairy item you purchased has been handled in any type of meat processing it would make it traif meaning not kosher.

well, while some of the above answer contain part of the answer, there is more to it.

There are different types of hechshers. i.e. parve, meaning not milk or meat, so it can be eaten with either or alone. Parve would also mean there is no time period to wait before eating something else. i.e. if f how you eat meat you have to wait a period of time before you can eat dairy. That length, the opinion of how long to wait will vary on the rabbi you ask. However, if you eat dairy first, there is not period of time to wait before eating meat. they cannot be eaten on the same plate at the same time.

There is also a kosher Dairy, which is indicated by a D or dairy next to the hechsher. There is the OU hechsher which is from the Union of Orthodox rabbis. Then there is a K hechsher, which is thought to be less stringent. There are many different reasons for them, but rarely will they be needed or required on fresh produce. However, not all fresh produce is of a kosher nature. The broccoflower (brocoli and cauliflower) is a hybrid, and therefore not kosher.

I hope this helps.

Generally speaking, foods (or ingredients) that are not in their natural state need a hecksher. Fresh tomatoes do not need a hecksher because they've just been picked from the vine without having anything done to them. (You just have to wash them carefully to be sure there are no bugs.) As for the other items you asked about, here goes:

Mustard: it's a processed food and therefore needs supervision in its production

Tunisian Pepper mix: the drying process should be supervised

Ketchup: it's a processed food

Chocolate syrup: it's a processed food

Peanut Butter: it's a processed food

Mayonnaise: it's a processed food

corn: fresh corn on the cob does not need a hecksher. (If it's organic though, you must strip it off the cob to be sure there are no bugs.) Canned corn is considered processed.

Chocolate powder: it's a processed food

Honey: does not need a hecksher

Spaghetti: it's a processed food

Hope this helps.

Sometimes because of the process of the industrialization they use pork Grease to lubrificate the machinery. Sometimes they use the same machine to process meat and milk products. Thats why they have someone to inspect the whole process.

You forgot to take your meds.. Right

Microscopic moving things...??

do the talk to you..too??

BTW you can not breath without taking in microscopic bugs Bacteria