Canning Without Sugar.
II.—Fruit juices may be preserved by gentle heating and after protection from the air in sterilized containers. The heat required is much below the boiling point. Professor Müller finds that a temperature of from 140° to 158° F., maintained for 15 minutes, is sufficient to render the fermenting agents present inactive. The bottles must also be heated to destroy any adherent germs. The juices may be placed in them as expressed and the container then placed in a water bath. As soon as the heating is finished the bottles must be securely closed. The heating process will, in consequence of coagulating certain substances, produce turbidity, and if clear liquid is required, filtration is, of course, necessary. In this case it is better to heat the juice in bulk in a kettle, filter through felt, fill the bottles, and then heat again in the containers as in the first instance. It is said that grape juice prepared in this manner has been found unaltered after keeping for many years. Various antiseptics have been proposed as preservatives for fruit juices and other articles of food, but all such agents are objectionable both on account of their direct action on the system and their effect in rendering food less digestible. While small quantities of such drugs occasionally taken may exert no appreciable effect, continuous use is liable to be more or less harmful.