Method for manufacturing edible oil deterioration preventing member, and edible oil deterioration preventing member

A method for preventing an edible oil from degrading, the method comprising the steps of:

• (A) producing an edible oil degradation-prevention member by
• (1) forming titanium nitride on the surface of a metallic titanium material or titanium alloy material by a heat treatment under a nitrogen gas atmosphere, wherein the heat treatment under a nitrogen gas is performed in the presence of an oxygen-trapping agent, at a heating temperature of 750° C. or higher, wherein the heat treatment comprises the steps of:
• (i) reducing the pressure in a furnace for heat treatment using a rotary-type vacuum pump, a mechanical booster pump, and an oil diffusion pump, and reducing the concentration of oxygen remaining in the furnace such that the pressure in the furnace becomes 0.1 Pa or less to create a decompressed furnace, and
• (ii) supplying nitrogen gas into the decompressed furnace to return the pressure in the furnace and heating the titanium material or titanium alloy material, and then alternately repeating steps (i) and (ii) at least once;
• (2) anodizing the metallic titanium material or titanium alloy material with the titanium nitride formed on the surface thereof obtained in step (1) by applying a voltage of 10 V or more in an electrolyte solution having no etching effect on titanium, thereby forming a titanium oxide film;
• and
• (3) heating the metallic titanium material or titanium alloy material with the titanium oxide film formed on the surface thereof obtained in step (2) at a temperature of 600° C. to 700° C. in an atmosphere selected from an air atmosphere, a mixed atmosphere of oxygen gas and nitrogen gas, and an oxygen gas atmosphere;
• wherein the titanium oxide film formed by the anodization is a crystalline titanium oxide film, and the crystalline titanium oxide film is an anatase-type titanium oxide film, and
• (B) (a) bringing the edible oil degradation-preventing member into contact with the edible oil during cooking to suppress the degradation of the edible oil,
• (b) reducing increases in the acid value (AV) of the edible oil,
• (c) preventing the edible oil from thermally degrading,
• (d) preventing deterioration of flavor and nutritional value of the edible oil, and
• (e) increasing the lifetime of the edible oil.