Among the most significant byproducts of the massive Florida citrus industry are the several essential oils which are of major consumer and economic importance. Investigations leading to the production of Florida citrus oils of highest quality and uniformity are reviewed with emphasis on the chemical and physical properties of the various types of oils. Some of the factors shown to affect the chemical and physical properties of expressed citrus oils were fruit variety, degree of maturity, seasonal variations, storage of fruit prior to extraction, seasonal rainfall, budwood, rootstock, method of extraction, and yield of oil. The chemical compounds identified to date in both Valencia orange and grapefruit cold-pressed oils are listed.Brief mention is made of the more recent use of spectrophotofluorescence in the identification and classification of citrus oils, along with ultraviolet spectra and evaporation residue relating to method of extraction and geographical origin.

Concentrated natural orange essences, commercially recovered in aqueous solutions, have aided in investigations of the volatile flavor of citrus juices. Analyses of chemical components, obtained in organic extracts, were performed by programmed temperature gas chromatography (PTGC). Retention temperature studies of the chemical spectrum employing two principal stationary phases, DEGS and Carbowax 20M, supplied tentative identification and peak assignments for 43 compounds. Application of a subtractive type analysis where the carbonyl constituents were removed chemically provided a less complex material for study. Improved PTGC resolution of the carbonyl-free essence facilitated additional peak assignments.

SUMMARY The flavor of orange juices was studied objectively through analyses of recovered volatile materials. Organic extracts of freshly recovered volatiles from juices of established varieties were shown with programmed‐temperature gas chromatography (PTGC) and thermal conductivity detection to contain 40–50 components. Aroma profiles of the different juices were obtained with a programmed‐temperature flame ionization gas chromatograph. Comparative evaluations were conducted of the flavor and aroma patterns of three varieties of Florida oranges: Hamlin, Pineapple, and Valencia. Preliminary investigation revealed no significant qualitative differences among varieties in gross analyses obtained with thermal conductivity an the ionization detection system using PTGC. Quantitative differences appeared responsible for the flavor differences noted among varieties. Analyses showed some compositional differences among varieties in control juices, peel‐oil‐free juices, their respective juice essences, and peel oils. The presence of certain chemical constituents in the juice was directly related to the peel oil. No significant qualitative differences existed in similarly prepared samples from different varieties. Some specific chemical identification and the methods used are outlined.

New information is presented concerning the chemistry of flavor relative to the processing of orange juices. Capillary column-flame ioniza-