Abstract: This paper investigated the effects of roasting time and grain size on the nutrients and quality of Yunnan Arabica coffee beans. The results showed that the content of nutrients such as ash, fat and protein increased with the increase of roasting time. In terms of quality, the weight loss ratio increased, the chromaticity values $ L^{*} $, $ b^{*} $, and $ \Delta E $ decreased, $ a^{*} $ increased first and then decreased, and the pH value of coffee liquor decreased first and then increased. Under the same roasting time, the ash content, pH value and fat content of small beans (diameter<5.6 mm) were generally higher than those of medium beans (diameter 5.6-6.7 mm) and big beans (diameter>6.7 mm), while the protein content of big beans was higher. According to the principal component analysis, the fat content had the highest comprehensive weight score, followed by the ash content, protein content, weight loss ratio and pH value. The above research provides data support for fine roasting and quality improvement of coffee beans.
Keywords: Yunnan Arabica coffee; grain size; roasting time; nutrients; quality