The "correct answer" is somewhere within the answers above. But I will try to simplify the language a little. Think norms. Whatever the norm is, speak about it in the negative. If the norm is that several students are in a class, you would say "There were no students in the class." If the norm is that one student does morning announcements, the teacher may say "There is no student to read the morning announcements today." If the norm is that food contains several preservatives and chemicals, you would say "There are no preservatives and chemicals." If it is the norm to use only ONE preservative agent in a certain canning process, the person or company doing the canning might say "There is no preservative in this yet." The exception would be if you are using indefinite pronouns, which are always singular: Ex.: "Nobody is in the class room."

Hello Joseph, You leave the sentence as it is. You are negating the fact that there are preservatives or chemicals. If you write the way you suggest: "There is no preservative to help it last longer or other chemical to make it." This means the affirmative form would refer to the existence of one preservative and a chemical substance only ,which is rarely the case with preserved food. By saying : "There are no preservatives to help it last longer or other chemicals to make it taste or look better. You are negating the affirmative form which would be: "There are preservatives to help it last longer and other chemicals to make it taste or look better." In English when you negate an affirmative sentence ,that is to put it in the negative form the singular or plural forms of the sentence don't change. Examples: There are 3 students in the class. There are no students in the class. Notice here that by negating the sentence the word 'students' remained in its plural form yet 'no' was used to indicate the negation. In case the sentence was: There is 1 student in the class. * here singular* There is no student in the class. * remains singular*

I think it all depends on what you want to emphasize. Both of them are correct in grammatical.

What I know is this: if you are refering to one preservative you need to say what you are talking about, as the same as chemical. And when you are talking in general aspects, this is the best way. You always have to be careful with the context. I hope this woukd be helpful for you!!! My name is Alberto Dos Santos, 39, Argentina