Apple Marmalade Secrets: How Natural Pectin Gives That Perfect GelThe secret to a thick apple jam that can be sliced like marmalade lies in natural pectin. Photo: Designed by Freepik by freepik, https://creativecommons.org/public-domain/pdm/ Apple jamIngredients2 kg tart-sweet apples1 kg sugarJuice from 1/2 lemonPreparationStep 1. Cooking tip: If your jam isn't thickening as expected, it may be due to a low pectin content in your specific apple variety. In this case, slightly extend the simmering time or add a bit more lemon juice to encourage the set. Store in a cool, dark place; under these conditions, the jam retains its quality and color for one year.