PROBLEM TO BE SOLVED: To increase the shelf life of a substance to be preserved, such as food, oil, and cosmetics, without oxidizing the substance and without adding a preservative or the like to the substance by electrolyzing a liquid by a method other than direct-current electrolysis. SOLUTION: A hydrogen generator equipped with a pair of AC electrodes and at least one first earth electrode in the liquid is used. The substance to be preserved or a container containing the substance is placed above the first earth electrode, and hydrogen is generated from the first earth electrode by applying alternating current to the pair of AC electrodes and bringing the first earth electrode to an earth potential. The hydrogen is absorbed by the substance to be preserved or the substance in the container; thus, the shelf life of the substance is increased without adding any preservative etc. to the substance and without oxidizing the substance. COPYRIGHT: (C)2004,JPO&NCIPI
