§ 156-c. Farm products; official standards. The commissioner is hereby authorized and empowered, after investigation and public hearing, to establish and promulgate official definitions and standards for grading or classifying, packing and labeling farm products, or any of them, packed or repacked within the state; and to change such official standards from time to time. The commissioner, in establishing such official standards, shall, among other things, take into account so far as applicable the factors of maturity, condition, soundness, color, shape, size and freedom from defects. Such official standards shall not be lower in their requirements than the minimum requirements of the official standards for corresponding grades or classifications, as promulgated from time to time by the secretary of agriculture of the United States, commonly known as U. S. grades. The use of such official standards when established shall be optional, but if and when used in relation to any farm products they must be in conformance with such standards.