Changes of physical properties of coffee beans during roasting

The effects of heating time on physical changes (weight, volume, texture and colour) of coffee beans (Outspan and Guaxupe coffee) were investigated. The roasting temperature of both samples was 170°C and samples for analysis were taken at the intervals of 7 minutes during 40 minutes of roasting. Total weight loss at the end of the roasting process was 14.43 % (light roasted) and 17.15 % (medium to dark roasted) for Outspan and Guaxupe coffee beans, respectively. Significant (P < 0.05) changes in the coffee bean breaking force values were noted between the 7th and 14th minutes, and statistically not significant (P > 0.05) between the 35th and 40th minutes of the roasting. According to the L* colour parameter as a criterion for the classification of roasted coffee colour (light, medium, dark), the Outspan sample was medium and Guaxupe sample was dark roasted.