Why small quantity of vegetable or mineral oil is added to stored grains of legumes?

A small quantity of vegetable or mineral oil is added to stored grains of legumes primarily to reduce moisture absorption and prevent spoilage. The oil creates a barrier that helps inhibit the growth of mold and bacteria, thus extending the shelf life of the grains. Additionally, it can help reduce the risk of insect infestation and enhance the overall quality of the stored legumes.