Effect of roasting temperature and duration on the physico-chemical and sensory properties of the coffee-guinea pepper roasted blend

Coffee is one of the most widely consumed products in the world. In Senegal, coffee-Guinea pepper roasted blend is consumed by over 70% of the population, making it the most widely consumed type of coffee. In view of its high consumption, coffee-Guinea pepper roasted blend is increasingly being marketed. The products on the Senegalese market often lack taste and aroma. Although the taste and aroma of the coffee-Guinea pepper roasted blend vary according to the species and origins of the coffee-Guinea pepper, an unmitigated roasting temperature and duration can alter their physico-chemical characteristics. To this end, the study of roasting temperature and duration on the physico-chemical characteristics of the coffee-Guinea pepper roasted blend is becoming an important area of research for all those involved in the sector. The effect of roasting temperature and duration on the physico-chemical characteristics of the coffee-Guinea pepper roasted blend is the subject of this study. To achieve this objective, four most popular samples on the Senegalese market were chosen. They were roasted at temperatures of 211 °C, 215 °C, 216 °C and 220 °C for 28, 25, 30 and 31 min, respectively. Fourier transform infrared spectroscopy (FTIR) in conjunction with energy dispersive spectrometry (EDXRF) were used to characterise the blend. The results showed the presence of more than 15 chemical elements, including nutrients such as calcium, potassium and magnesium, as well as heavy metals at trace levels. The results also show that roasting temperature and duration influence the concentration of these elements. Potentially toxic elements can appear at high temperatures. A relatively long roast at high temperatures leads to a darker coffee with richer, bitter notes. Low temperature and long duration lead to a more balanced blend of coffee-Guinea pepper roasted blend with less bitterness. Moderate temperature and duration result in a lighter coffee-Guinea pepper roasted blend with more subtle aromas. Optimal roasting conditions are determined at 215°C for 25 min, characterised by a balance between bitterness and more subtle notes. Key words: Characterization, Coffee, Fluorescence, Guinea pepper, Infrared, Roasting, Spectroscopy, Temperature