Setting Agent Extracted From Fruit
Puzzle 18 of Classic Things Medium Pack
Question is: Setting Agent Extracted From Fruit
and the answer is: PECTIN
Word Meaning:
PECTIN — (biochemistry) A polysaccharide extracted from the cell walls of plants, especially of fruits; under acidic conditions it forms a gel. It is often used in processed foods, especially jellies and jams where it causes thickening (setting).
Definitions from Wiktionary.