Critical Evaluation of Coffee Pulp as an Innovative Antioxidant Dietary Fiber Ingredient: Nutritional Value, Functional Properties, and Acute and Subchronic Toxicity

Coffee pulp is a by-product generated during coffee processing, producing environmental pollution when discarded to rivers. Currently, the revalorization of coffee by-products is being studied due to its high potential as new value-added food ingredients. This work aimed to study the chemical composition and functional properties of coffee pulp, including antioxidant, hypoglycemic and hypocholesterolemic properties, as well as to validate the safety of coffee pulp as a novel food ingredient.

Coffee pulp composition was assessed following the standard methods (AOAC). Determination of dietary fiber (DF), including the soluble and insoluble fraction, was performed using enzymatic-gravimetric and chemical methods. Total phenolic compounds and in vitro antioxidant capacity were analyzed by Folin-Ciocalteu and ABTS, respectively. Physicochemical properties measured included bulk density, water holding capacity, oil holding capacity, water absorption capacity, swelling capacity, emulsifying activity, foaming capacity, and gelation capacity. Hypolipidemic (cholesterol and bile salts binding and lipase inhibition capacities) and hypoglycemic (glucose adsorption and the inhibition of α-amylase, glucose diffusion, and starch hydrolysis) were investigated using in vitro techniques. Acute and subchronic oral toxicity experiments were carried out following OECD Test Guidelines 452 and 408 (5 male and 5 female C57BL/6 mice per group, vehicle/coffee pulp) to assess the food safety of coffee pulp flour.

Coffee pulp showed a high content of DF (51.2%), highlighting the fraction of insoluble dietary fiber (88.9%) compared with soluble dietary fiber (11.1%). Proteins (9.2%) and lipids (2.6%) were considered a min fraction. Coffee pulp presented a high content of phenolic compounds (40.6 mg/g), of which 29% were linked to DF, giving coffee pulp its antioxidant potential (102.3 mg Trolox eq/g). The by-product showed adequate water and oil retention and gelling properties. Coffee pulp reduced the absorption of cholesterol (84%) and bile salts (85%), inhibited pancreatic lipase (64%), and presented the capacity to diminish the diffusion of glucose (34%). The acute and subchronic toxicity tests revealed that the intake of coffee pulp did not cause significant lesions in isolated vital organs (liver, spleen, and kidney) nor changes in histological parameters, guaranteeing the safety of this new food ingredient.

The results obtained motivate the use of coffee pulp as a novel ingredient with a high content of antioxidant dietary fiber, and great potential to be safely incorporated functional foods with beneficial health properties.