The object of this application is to non-enzymatically improve flavor of a butter oil and fat composition. The present invention can enrich lactones in the oil and fat composition by the following steps of keeping temperature of the oil and fat composition containing between 300 ppm and 1200 ppm of moisture content at the temperature where a solid fat exists in the oil and fat composition, and non-enzymatically producing ³-lactone or ´-lactone from triglyceride containing 4- or 5-hydroxy fatty acid in the oil and fat composition, or adding to the oil and fat composition an additive agent (such as, sucrose) which has an ability to form hydrogen bonds with water molecules, keeping temperature of the oil and fat composition at the temperature between 40 and 60°C, and non-enzymatically producing ³-lactone or ´-lactone from triglyceride containing 4- or 5-hydroxy fatty acid in the oil and fat composition.
