(1) In food technology, the addition to a foodstuff of various nutrient substances during manufacture to increase the dietary value of the food, e.g., addition to wheat flour of vitamins B1, B2, niacin, and iron. In this way, the food is brought up to a specific nutritional standard. (2) Increase in the abundance of certain isotopes of an element by any of several methods: (a) By a chemical reaction accompanied by irradiation from a laser beam; enrichment of boron, chlorine, and sulfur isotopes has been achieved in this way in a number of research laboratories. Uranium enrichment is also possible, either by adding previously prepared 235U to natural uranium or by the laser technique. (b) Uranium can also be enriched by gas centrifugation and gaseous diffusion. The latter is the usual procedure. (3) Addition of oxygen to air to increase its combustion-supporting ability.