Sampling Method for Analysis of Coffee Volatiles by Gas Chromatography

Abstract

The aroma of coffee is of prime importance from the point of view of the consumer. The aroma not only produces a pleasing sensation by itself, but plays an important role in the acceptance of the brewed coffee. The flavor of brewed coffee is, in fact, a combination of the two senses, taste and smell. The aroma of coffee involves only the sense of smell and is, therefore, limited to the so-called volatiles in roasted coffee. Many of the compounds present in coffee aroma have been identified by various investigators (2, 3, 5 ) , but little information of a quantitative nature has been obtained, primarily due to inadequate methods of analysis. With the introduction of gas phase chromatography, a method of analysis for extremely small quantities of material has become available. The use of gas chromatography as a means of separation of the volatile constituents of onions and irradiated meat has been reported by Niegisch and Stahl ( 4 ) and Stahl et al. (6). Dimick and Corse (1) used gas chromatography to separate the volatile constituents of strawberries. The quantitative measurement of a rather large number of coffee volatiles can be made in a comparatively short time by this technique and much information can be obtained as to the effects of roasting times and temperatures on different varieties of coffee, the nature of staling of coffee, storing and packaging of roasted coffee and the similarities and/or differences of regular and instant coffee. A sampling technique has been developed which produces characteristic and reproducible chromatograms of the volatiles obtained from ground roasted coffee. Since it is thought the sampling technique may be of help to others working on coffee production or research problems, the writing of this report does not await identification of all peaks obtained on the chromatograms. The method appears to be readily adaptable to flavor and odor problems of other food and beverage industries. EXPERIMENTAL Apparatus. The gas chromatographic instrument used was a Perkin-Elmer "Vapor Fractometer" Model 154 with an external gas sampling valve which is available as an accessory. Helium was used as the sweep gas at a rate of 100 cc. per minute. The column operating temperature was 45°C.Since it is not the purpose of this report to discuss the theoretical aspects of gas chromatography, readers with an interest in this aspect arc referred to A. 1. M. Keulsmans, Gas ChrowatogruQhy (Reinhold). Preparation of column. The partitioning column used in this work consists of JohnsMansville C22 fire brick as the solid support and Carbowax 1500 as the stationary liquid phase, in two meters of The C22 fire brick was crushed and sieved to 40-60 mesh, water-washed, and then resieved. The dried brick was then coated with Carbowax 1500 in the ratio of 4 parts brick to 1 part Carbowax. Coating of the brick was accomplished by dissolving a predetermined amount of Carbowax in sufficient methyl alcohol to just completely wet the brick. The bulk of the alcohol was evaporated in a steam bath with constant stirrin...

Coffee, cocoa, and tea

“…Year of discovery and Coffee 1898 (22) 1958 (29) 1966 (34) Cocoa 1962 (115) 1968 (125) 1971 (124) reference Tea 1974 (200) 1974 (200) 1970 (186) 1937 (160) 1974 (200) 1974 (200) 1958 (166) 1935 (157) 1974 (200) 1981 (207) 1974 (201) 1965 (173) 1957 (163) 1967 (180) 1974 (200) 1974 (200) 1963 (168) 1974 (200) 1957 ( Year of discovery and Coffee 1984 (65) 1967 (42) 1967 (42) 1967 (42) 1967 (42) 1967 (42) 1967 (42) 1967 (43) 1937 (26) 1966 (57) 1982 (52) 1967 (42) 1982 (52) 1966 (34) 1982 (52) 1983 (58) 1982 (52) 1983 (58) 1967 (42) 1967 (42) 1967 (42) 1976 (47) 1959 (84) 1968 …”

“…Year of discovery and Coffee 1967 (42) 1967 (42) 29 Cocoa 1964 (120) 1967 (122) 1964 (120) 1968 (123) 1968 (123) 1968 (123) (186) 1974 (200) 1974 (200) 1974 (200) 1970 (186) 1963 (168) 1974 (200) 1970 (186) 1967 (181) 1972 (190) 1967 (140) 1967 (181) 1973 (197) 1971 (188) 1967(181) 55 reference Tea 1967 (140) 1974 (199) 1967 (180) 1974 (199) 1973 (198) 1973 (198) 1974 (199) 1974 (201) 1974 (200) 1974 ( (120) 1964 (120) 1968 (125) reference Tea 1973 (198) 1983 (208) 1974 (201) 1973 (198) 1973 (198) 1971 (188) 1967(180) 16 reference Tea 1966 (177) 1972 (191) 1971 (188) 1971 (188) 1972 …”

Stepwise Discriminant Analysis of Gas Chromatographic Data as an Aid in Classifying the Flavor Quality of Foods

“…NUMEROUS INVESTIGATORS have observed gas chromatographic differences in the volatiles of foods known to differ in quality or processing method. Typical of such observations are comparisons of brewed coffee and coffee in the can, fresh and imitation banana, and good-and poor-quality bourbon (Mackay et al, 1961) ; different coffee samples (Rhodes, 1958) ; two varieties of bananas at four stages of maturity (McCarthy et al, 1963) ; alcoholic beverages of different types (Bober et al, 1963(Bober et al, , 1964 ; turkey and chicken products (Pippen et al, 1963) ; three varieties of oranges (Wolford et al, 1963) ; fresh and canned corn, fresh and off-flavor potato granules, and two varieties of pear (Buttery et al, 1961) ; and age of dry-cured hams (Ockerman et al. 1964).…”

La cire cuticulaire des grains de raisin et des feuilles de la vigne

“…On peut rattacher à ce paragraphe le travail intéressant de RHOA-DES (61).Cet auteur étudie les substances volatiles du café moulu se trouvant dans un bain-marie à 100°C. Ces substances sont entraînées par un courant d'hélium humide et condensées en tête d'une colonne de Carbowax, elle-même plongée dans de l'azote liquide ; après réchauffe¬ ment de cette colonne, le gaz carbonique élué en tête est éliminé, les substances odorantes sont piégées à -196°C et elles sont étudiées par chromatographie en phase gazeuse ; l'eau est éluée en dernier.…”