QUALITY ENHANCEMENT OF COFFEE BY ACID AND ENZYME TREATMENTS
Coffee is one of the most consumed beverages in the world, and is a world-wide trade commodity. Coffee processing has been an art, with only recent scientific interest to understand the many chemical and physical mechanisms involved. Also, there has been an increasing demand for specialty coffee from different origins and roasted differently.
Kopi Luwak is the most exotic and expensive coffee known, with a price range from $600 to $1200/Kg. Its annual production is only about 150 Kg. This coffee is produced by a marsupial called Luwak, who eats and partially digests the ripest coffee cherries and excretes them into the fields. This partially “processed” coffee is picked, cleaned, and roasted. It is believed that the acids and enzymes in the digestive tract of the Luwak cause its unique aroma and taste. If the chemical and physical principles behind the transformation of the beans through the Luwak can be understood, then this process can be achieved without the Luwak, in a more controlled, consistent, and economical way.
The objective of this project was to initiate the research to develop a coffee processing technology, which enhances the flavor and aroma of coffee by acid and enzyme treatments, and to quantify the effects of these treatments by sensory analysis, electronic nose, color analysis and scanning electron microscope analysis.
Coffea Arabica L, Limani variety was cultivated and harvested at the University of Puerto Rico’s “Experimental Station” in Adjuntas, PR. The coffee was treated with Pepsin and HCl. The treated coffee and its controls were roasted using an Ambex Y-15 roaster to 228 oC for 18 minutes. Taste panels were performed using a triangle test to detect significant differences, and a trained panel to quantify changes in bitterness. Sensory analysis showed that treated samples were significantly less bitter than controls. An electronic nose was used to sniff the headspace of samples. Discriminant function analysis of e-nose data resulted in a good separation between treated and control samples. A scanning electron microscope (SEM) was used to analyze the surface of the green treated beans and controls, showing that the enzymes penetrated the beans and affected the surface. Color and texture primitives, and contours of images of the treated samples and its controls of the SEM images were analyzed with ANOVA. Significant differences were found between treated and control samples. A machine vision system was used to measure color of green and roasted beans before and after treatments. For green and roasted beans significant differences for L*, a*, and b* values were found between treated and control samples.
Acids and enzymes can be used to treat coffee beans and enhance the aroma and flavor, and reduce the bitterness of coffee. The next step is to quantify the changes using GC-O, GC-MS for aroma compounds, and HPLC for chlorogenic and other acids, to optimize the acid and enzyme treatment combinations and to do a trained panel for consumer preference.
The development of this method to consistently enhance the quality of coffee will be of great significance scientifically and industrially. This process would be able to produce coffee of the highest quality and will be able to be scaled for commercial applications, which will help the development and enhancement of value added agriculture in the US, as well as the agricultural sector of different countries by the production of a commodity of higher value.