Optimisation of <i>Senna Occidentalis</i> L. Seed Roasting Using the Response Surface Method

The aim of the study was to define the optimum conditions for roasting Senna occidentalis seeds for the production of coffee substitute; ground ‘negro coffee’. A centred composite design was used to assess the effects of roasting temperature and time on secondary metabolites (polyphenols and flavonoids), antioxidant potential and the colour of ‘senna coffee’. The roasting temperature and time were varied from 190 to 210°C and 10 to 20 minutes respectively. Multiple regression models were developed using response surface methodology (RSM). The results visualised with the response surface graphs show that temperature and time significantly influence the recorded responses. The optimum conditions for roasting the seeds to produce ‘senna coffee’ are 194.206°C and 14.33 minutes. Under these conditions, the predicted polyphenol content, free radical scavenging activity, and colour difference were 2.419 mg EAG.g-1, 53.89%, and 24.98 respectively.