Prick them somewhat deeply with a small, pointed stick (in order to precipitate the cooking process), and throw them into a preserving pan of boiling water. Boil for thirty minutes; drain the oranges, cool them, and put them under a running tap for twelve hours, or more if possible; or soak them in constantly changed, cold water for twenty hours. The object of this operation is to soften the rinds and extract their bitterness.
This done, drain the oranges; quarter them, remove their pips and filaments, and rub them through a coarse sieve.
Take the same weight of sugar as of orange purée. Melt the former in the preserving pan, and boil it for five or six minutes, skimming carefully the while. Then add the orange purée, and one-quarter pint of good apple juice per lb. of the former.
During the first stage of the cooking process, skim with great care, and during the second stage, stir almost incessantly until the “[nappe]” stage is reached.
[2960—PLUM JAM]
Allow twelve oz. of loaf-sugar per lb. of stoned plums.
Dissolve the sugar; skim, set it to boil for seven or eight minutes, and proceed for the cooking as directed under apricot jam.
Remarks:—(1) It is a mistake to let the plums macerate in the sugar for some hours previously, for the acid they contain causes them to blacken, and the colour of the jam is thus spoiled. (2) In order to have greengage jam of a fine, green colour, do not cook more than from six to eight lbs. of it at a time, and cook that quantity as quickly as possible.
[2961—RHUBARB JAM]
Rhubarb jam is one of the most difficult and tedious to make owing (1) to the abundant moisture contained by the vegetable; (2) to its proneness to burn on the bottom of the saucepan, especially towards the close of the cooking process.