Complex sentence: Margarine has a particular market value to those who observe the Jewish dietary laws of Kashrut, which forbids the mixing of meat and dairy products; hence there are strictly Kosher non-dairy margarines available.
Split into simpler sentences: Margarine has a particular market value to those who observe the Jewish dietary laws of Kashrut. Kashrut forbids the mixing of meat and dairy products; hence there are strictly Kosher non-dairy margarines available.