Production of volatile organic compounds by apples

There is great variation in the rate at which different apple cultivars produce volatiles. The rate of production of volatiles, in terms of loss of carbon, is some 0.3–1.0% of the loss of CO₂; depending on conditions of storage, some 50–95% of the carbon lost as volatiles is accounted for by ethylene. Increase in concentration of CO₂ in the storage atmosphere reduces the rate of production of volatiles. Reduction of the oxygen concentration to a low level has the same effect, and ethylene production ceases in the complete absence of oxygen. The peel of the fruit is more active in production of ethylene than is the pulp; the rate of production is greater for small apples than for large. When the volatiles are removed from the storage atmosphere, the rate of production increases. The incidence of superficial scald, and the shape of the time/rate graph for ethylene are related. This could be due to an effect of climate during the growing period, affecting the porosity of the peel.