Sustainable Ultrasound Assisted Extractions and Valorization of Coffee Silver Skin (CS)

Abstract

The Sustainable Development Goals (SDG) encourage the efficient use of sustainable technologies. Ultrasound-assisted extraction (UAE) is one of the extraction process techniques, which are also directed towards sustainability as a goal. Coffee silver skin (CS), being a healthy raw material as well as a waste, could be utilized in the manufacturing process of new dietary products. The goal of this research was to isolate proteins and polyphenols from CS using UAE and to employ spectrophotometry to determine the yields. Three parts of the research were conducted: ultrasonic extraction, the optimization of UAE conditions for the isolation of proteins and polyphenols from CS, and the analysis of the amino acid extract obtained with the optimal use of UAE. According to the results, it was reported that the highest yields of total polyphenols isolated from the CS using UAE were obtained by applying an amplitude of 75% and a time interval of 9 min. The optimal parameters of UAE, when considering the proportions of total polyphenols and proteins, are an amplitude of 100% and a time of 9 min. The most abundant amino acids in isolated proteins (Asp, Glu, Pro, Gly, and Ala) were defined as well. Based on the use of energy, it was obvious that UAE is a promising technology. This concurs with the proposed practice that when non-thermal technologies are analyzed from an environmental point of view, the first common denominator is the use of electricity to run the equipment, in relation to resource depletion. As expected, CS poses a great waste to be recycled, being a nutritionally rich raw material with great potential. Quantitative consideration on the environmentally friendly applicability of CS in mass production should be carried out to validate the entire process of developing a new product from both economic and environmental aspects.