An Impression of Coffee Carbohydrates

Coffee is one of the most popular beverages in the world. It is consumed for its refreshing and stimulating properties. Carbohydrates are the major constituents of coffee beans and serve various functions like binding of aroma, stabilization of foam, formation of sedimentation, and increased viscosity of the extract. The principal low molecular weight carbohydrate is sucrose and no evidence of other simple oligosaccharides has been found. Polysaccharide fraction from green coffee is dominated by arabinogalactan, galactomannan, and cellulose. The polysaccharide content is reduced during roasting due to degradation to low molecular weight carbohydrates (viz., mono and oligosaccharide) and become more extractable. Various methods that can be employed to extract the carbohydrate from roasted coffee are sequential extraction, acid hydroloysis, hot water extraction, enzymatic extraction etc. Carbohydrates from coffee can be quantitatively determined by liquid chromatography, high performance anion exchange chromatography, size exclusion chromatography, and high performance liquid chromatography. Besides improving the organoleptic quality of the coffee beverage, carbohydrates also possess various biological activities such as lowering colon cancer risk. Besides their sheer mass, a variety of evidences testify to the important contribution that the polysaccharide content makes to the character of the final brew. Although a number of chemical and enzymatic methods have been devised to isolate and quantify the carbohydrates of R&G coffee, till date hot water extraction is the only method which can be accepted as a most feasible process and hence, there is wide scope of further research for the efficient and economically viable technology for extraction of carbohydrates from coffee.

Keywords:

• coffee
• green and roasted beans
• chemical composition
• carbohydrates
• isolation
• extraction
• biological activities

ACkNOWLEDGEMENTS

The authors are thankful to Dr V. Prakash, Director, Sri B. Raghavan, Head, Plantation Products, Spices and Flavour Technology, and Dr M.C. Varadaraj, Head of Human Resource Development Department, Central Food Technological Research Institute, Mysore for their keen interest and encouragement.

Notes

^a Dry Green Beans.

^b Not corrected for dry weight roasting loss, which varies form 2–5%.