Optimization and comprehensive investigation of coffee from date seeds and olive seeds: an alternative to Turkish coffee

Abstract This work aimed to develop a sustainable, acceptable, and nutritionally rich coffee from agricultural by-products of date seeds and olive seeds. The olive seeds was utilized for the first time and its effects were investigated in this study. Using Response Surface Methodology, date seeds and olive seeds powders were blended through a mixture design approach and evaluated in terms of total phenolics content (TPC), total flavanoid content (TFC), radical scavenging activity (RSA) by DPPH and ABTS, foam stability, foam volume, and acidity. Numerical optimization was conducted to produce an optimum coffee formulation with the highest RSA, highest TPC, highest foam volume, and lowest acidity. The formulation of the optimum coffee was predicted to contain 7.35 g date seeds and 4.64 g olive seeds, with an experimental TPC of 0.207 mg GAE/g dry solids, RSA of 84.86%, acidity of 12.80 mL NaOH/100 g DS, and foam volume of 3.7 mL. Based on the results, the optimum coffee exhibited 2.4 times higher antioxidant activity and significantly reduced acidity compared to Turkish coffee. According to the sensory evaluation, the optimum coffee received the second-highest scores after Turkish coffee for all sensorial attributes. The purchase intention score of 4.42 out of 7 corresponds to the expression “I can buy the product.” Surprisingly, Pearson’s correlation test revealed that although date seeds was the primary contributor of phenolic compounds, olive seeds played a dominant role in enhancing antioxidant activity. The present study not only offered a healthier alternative but also a sensorially acceptable coffee product for consumers while supporting sustainability. Graphical Abstract