Validation of Cocoa Shell as a Novel Antioxidant Dietary Fiber Food Ingredient: Nutritional Value, Functional Properties, and Safety

To study the nutritional value of cocoa shell, analyzing the chemical composition and functional properties as antioxidant, hypoglycemic and hypocholesterolemic effects, as well as validate the safety of cocoa shell as a sustainable food ingredient. Proximate composition was determined following the AOAC methods. Soluble and insoluble fractions of dietary fiber (DF) were determined using enzymatic-gravimetric and chemical methods. The phenolic profile was analyzed by UPLC-MS/MS and antioxidant properties were tested using ABTS. Furthermore, physicochemical, hypoglycemic, and hypocholesterolemic properties were assessed in vitro. Acute and subchronic oral toxicity experiments were performed following OECD Guidelines 452 and 408 (5 male and 5 female C57BL/6 mice per group, vehicle/cocoa shell) to assess the food safety of cocoa shell flours. Cocoa shell was composed of carbohydrates (62%), proteins (16%), and fat (2%). DF represents 59%, being the insoluble dietary fiber (IDF) the main fraction (82%). IDF fraction was constituted by lignin (58%) and polysaccharides (42%); cellulose was inferred as the main polysaccharide of IDF, followed by hemicelluloses (arabinans and galactans). High content of phenolic compounds (33.7 mg/g) was shown, being a significant phenolic fraction (51%) bound to DF, which confers cocoa shell its antioxidant potential (73.1 mg Trolox eq/g). The main phenolics were protocatechuic acid, (–)-epicatechin, and (+)-catechin. Cocoa shell exhibited adequate water and oil holding properties to be included in food matrices. During in vitro digestion, starch hydrolysis and dialyzed glucose diminished (34 and 13%, respectively) due to α-amylase inhibition (18%) and glucose adsorption (31%). Cocoa shell also inhibited cholesterol and bile salts absorption (72 and 70%, respectively). The intake of acute (2000 mg/kg) and subcronical (1000 mg/kg) doses of the ingredient did not cause significant lesions in selected isolated vital organs (liver, spleen, and kidney) nor changes in histological parameters, ensuring the safety of this sustainable food ingredient. Results validate the use of cocoa shell as an antioxidant dietary fiber ingredient, being a safe potential candidate to be incorporated in the development of foods for specific health uses. Ministry of Science and Innovation.