Abstract
Coffee husks are a major by-product of coffee production and are currently being underutilized. The aim of this work was to chemically characterize coffee husks to allow for an adequate evaluation of their potential for valorization. Blanched and non-blanched coffee husks were characterized for extractable and non-extractable phenolics, caffeine, trigonelline content, and for their polysaccharide and proximal composition. The total, soluble and insoluble fiber contents were determined, together with the husks’ technological properties. Antioxidant activity and bioaccessibility of phenolic compounds of coffee husks were evaluated. Two types of husk were studied: one comprised mostly of outer skin and pulp (CH1); and other comprised mostly of parchment (CH2). Blanching had positive effects on non-extractable phenolics, chlorogenic acid and on the bioaccessibility of phenolics, promoting small reductions in extractable phenolics, protocathecuic acid, caffeine and trigonelline contents. Blanched CH1 presented more appropriate properties than CH2 for potential applications in food. It also presented better antioxidant, hydration, and oil holding properties than those of other agri-food by-products. Tentatively identified polysaccharides included galactomannans, arabinogalactans type II, pectin and cellulose.
Highlights
Coffee is one of the main commodities in the world in terms of revenue, second only to petroleum, being consumed by approximately a third of the world population [1,2]
Dry processing is the most common technique applied to coffee fruits [2], with main by-product being comprised of dried pulp and parchment and it is denominated coffee husks (CH)
High concentration of phenolics in the outer skin is expected since the primary function of these metabolites is protection against external threats [26]
Summary
Coffee is one of the main commodities in the world in terms of revenue, second only to petroleum, being consumed by approximately a third of the world population [1,2]. Vietnam, Colombia and Indonesia are the largest producers in the world [2]. Coffee processing generates large amounts of by-products. Dry processing is the most common technique applied to coffee fruits [2], with main by-product being comprised of dried pulp and parchment and it is denominated coffee husks (CH). Dry processing generates approximately 1 kg of CH per kg of coffee beans produced [3]. The adequate allocation of these by-products contributes to a sustainable production, since these can cause serious environmental problems due to their content of highly bioactive compounds such as caffeine and trigonelline [4]
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