Advances in Fruit Flavor Chemistry

Abstract

Advances in separation, physical measurement equipment, and manipulation techniques have overcome some of the difficulties encountered in fruit flavor research. Capacity of high resolution gas chromatography columns has been increased. Gas chromatography and mass spectrometry have been combined to give information with submicrogram quantities. Sample sizes required for proton magnetic resonance studies have been reduced to submilligram quantities. A flavor component of Bartlett pears has been identified. Most of the volatile constituents of mandarin peel oil and lime oil have been identified.The constituent mainly responsible for grapefruit aroma has been identified as nootkatone. The chief bitter principle of grapefruit, naringin, has been changed to an intensely sweet compound, a chalcone.The quantities that one deals with in aroma chemistry research vary greatly: in one phase of the research, tens of tons of fruit are extracted and concentrated for the volatile constituents; in another, as little as tenths of nanograms are separated and detected in the vapor from a single fruit. This is indeed a staggering ratio, comparable to the ratio of the earth's diameter to that of an atoml Because the concentration of the compounds responsible for the desirable aroma of fruits is small, even though we start with large amounts of raw material, only very small amounts of pure material are isolated. Thus, assignment of chemical structure is difficult, and the degree of certainty of the assignment decreases with decreasing amount of material isolated and purified. However, advances in gas chromatographic separations and in physical measurement equipment and techniques are now being applied in the field of fruit flavor chemistry, and the impact of obtaining more information with much less material than previously necessary is just now being felt.