What is meant by a pectic substance?

Pectin is a natural gelling agent which is found in fruits. It occurs in higher concentrations in some fruits than others, with those of the citrus family being high in pectin. Crab Apples also contain more than average amounts.

Pectin can be extracted from these fruits, refined and then either bottled or powdered to be added as a gelling agent when making low-pectin fruit jams and jellies. Rather than using refined pectin, it is also possible to add lemon juice to a recipe to make the jelly 'set' although this can give a definite lemony taste to the finished jelly, whereas refined pectin is almost tasteless when cooked.

So, a pectic substance could either be a fruit containing high amounts of pectin, such as crab Apples or lemons, or it could be a concentrated form of pectin, such as a bottled or powdered gelling agent.