Phenolic compounds from coffee by-products: Extraction and application in the food and pharmaceutical industries

Background: Coffee by-products are generated along the coffee production chain, from harvest to brewing. The presence of phenolic compounds, caffeine, and flavonoids in coffee and its by-products has attracted attention with respect to their applications in foods and pharmaceutical matrices, especially considering the bioactive potential of these molecules. These by-products can be used as ingredients to reduce the environmental impact of coffee production, add value to coffee waste, and provide wider options for consumers who are increasingly seeking foods with "natural" and bioactive ingredients.Scope and approach: In this review, recent studies of the extraction of phenolic compounds by conventional and non-conventional methods, including emerging technologies, as well as the application of coffee by-products in the food and pharmaceutical industries, are described. In particular, we focus on several recently developed extraction techniques that have been optimized to provide greater yields, lower the environmental impact of extraction, and enable the better reuse of by-products of agricultural origin.Key findings and conclusions: The phenolic compounds in coffee by-products can be obtained by different extraction techniques, including conventional (solid-liquid and liquid-liquid) and non-conventional (ultrasound, microwave, supercritical fluid, subcritical water, pulsed electric field, and fermentation) methods. The main phenolic compounds reported in coffee by-products are chlorogenic acid and its derivatives. Bioactive compounds from these by-products can be used in the production of beverages, dairy products, and baking products as antioxidants and colorants, as well as in the pharmaceutical industry; in addition, they have applications in anti-aging and anti-wrinkle products and as protective agents in different cosmetics.