scientists have found that the optimal
conditions for pectin gelation are a pH
between 2.8 and 3.5 — about the acidity of
orange juice, and 0.5% acid by weight — a
pectin concentration of 0.5 to 1.0%, and a
sugar concentration of 60 to 65%.
Preparing Preserves Preserve making begins
with cooking the fruit to extract its pectin.
Quince, apples, and citrus fruits are especially
rich in pectin and often included to
supplement other pectin-poor fruits, including
most berries. The combination of heat and
acid will eventually break pectin chains into
pieces too small to form a network, so this
preliminary cooking should be as brief and
gentle as possible. (If a sparkling, clear jelly
is desired, then the cooked fruit is gently
strained to remove all solid particles of cell
debris.) Then sugar is added, supplemental
pectin if necessary, and the mixture rapidly
brought to the boil to remove water and