Microstructural Modification of Green Coffee Beans through Drying and Puffing

Abstract

Abstract The aim of this study was to explore a new method for changing the flavor of coffee between post harvesting and roasting process. As a preliminary study on the introduction of foreign flavor components, four methods were used to process Kenyan green coffee beans with high water content: drying, freeze-drying, short-time heating puffing, and microwave puffing to modify the structure of green coffee beans. The color change and porosity of the modified green coffee beans were then studied, and the microstructure of the beans was observed using a scanning electron microscopy. The study found that the ΔE* value of the modified green coffee beans was lower than 9.47, which is the ΔE* value of light-roasted coffee beans. Except for the green coffee beans treated with short-time heating (3 min) puffing, the ΔE* value of the modified green coffee beans was lower than 6.53. In addition, coffee beans that underwent short-time heating (1 or 2 min) puffing and microwave puffing had higher porosity and looser microstructure. The green coffee beans with a moisture content of 38.77% had a porosity of 21.77% and 32.64% after being short-time heating (2 min) puffed and microwave puffed, respectively. In conclusion, short-time heating for 1 or 2 puffing and microwave puffing were effective methods for changing the microstructure of green coffee beans.