ISSN:
1750-3841
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
SUMMARY— Volatile aliphatic acids (C1 to C10) were determined in the beverages from three varieties of coffee- Colombian, Santos, and Robusta. Formic acid was determined by NMR, the remainder by gas chromatography. The difference in acid concentration between medium- and dark-roasted coffees was also examined. Acetic acid and formic acid are found to be the major volatile acid components; C3 to C10 acids are present only in relatively small amounts in the three varieties investigated. Robusta coffee was found to be significantly higher in formic acid and slightly lower in acetic acid than Colombian and Santos.In general, the dark roasts were lower in volatile acids than the medium roasts and Robusta had the highest total volatile acid content. No significant differences were observed between Colombian and Santos. Although measurable differences in acidity were found among the different varieties and between the two degrees of roasting by titration of beverages to pH 9.0, the volatile acids were found to be too low in concentration to account for these variations. It was assumed that the major acid components must be nonvolatile acids. This has been confirmed by analysis of nonvolatile acids which will be published later.The method used involves neutralization of the coffee beverage with sodium hydroxide, precipitation of emulsion-forming materials with methanol, and lyophilization of the supernatant liquid. The freeze-dried solids are treated with excess mineral acid and extracted with ethyl ether. The ether extract is then analyzed for volatile acids by gas chromatography and by NMR. Both gas chromatography and NMR methods are sensitive and quantitative, and require less than 30 min to complete an analysis once the sample preparations have been completed. This technique should be useful for the determination of volatile acids in fruits, vegetables, and other biological substances.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2621.1967.tb09710.x
Permalink