2. The fruit juice must contain a certain amount of pectin, or jellying principle, and also a certain amount of acid.
"Ontario Teachers' Manuals: Household Management"
Ministry of Education
94. pectin in fruit juice.
"School and Home Cooking"
Carlotta C. Greer
95. pectin in the inner portion of orange and lemon peel.
"School and Home Cooking"
Carlotta C. Greer