The effects of roasting temperature and time on quality attributes of Sumberjambe robusta coffee

Robusta coffee originating from Sumberjambe possesses several superior clones, such as Tugusari, BP912, Brazil, and BP42, which offer substantial opportunities for exploring agronomic characteristics and yield quality. The local agroclimatic conditions—with ideal rainfall and an elevation of 600–650 meters above sea level—are highly suitable for robusta cultivation, thereby supporting optimal production and bean quality. In addition, Sumberjambe robusta beans are large in size and meet national quality standards (SNI), indicating high physical quality and strong potential for increased economic value. Sumberjambe Subdistrict in Jember is a notable coffee-producing region, yielding 113 tons per year from 214 hectares, with an average productivity of 0.65 tons per hectare. Given the high production potential, optimizing the factors influencing coffee quality in Sumberjambe is essential. This study aimed to optimize roasting temperature and duration affecting coffee quality attributes. Coffee quality was assessed based on physical properties, yield, and caffeine content. A completely randomized design (CRD) with two factors was employed: roasting temperature at three levels (160°C, 170°C, and 180°C) and roasting time at three levels (10, 12, and 14 minutes), each with three replications. Observed parameters included color, moisture content, density, and caffeine concentration. Analysis of variance indicated highly significant effects of roasting temperature and time on color, moisture content, and yield. The optimal roasting condition was 170°C for 10–12 minutes, producing beans with balanced color, acceptable moisture content (1.3–1.4%), stable yield (~0.55), and desirable caffeine concentration (2.18–3.34%). These results indicate that precise control of roasting parameters is essential to maintain consistent quality and optimize the sensory characteristics of Robusta coffee. These findings provide valuable insights for optimizing roasting conditions to enhance coffee quality in Sumberjambe.