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Waste mitigation: From an effluent of apple juice concentrate industry to a valuable ingredient for food and feed applications

Cruz, Marco G., Bastos, Rita, Pinto, Mariana, Ferreira, João M., Santos, João F., Wessel, Dulcineia Ferreira, Coelho, Elisabete, Coimbra, Manuel A.
Journal of cleaner production 2018 v.193 pp. 652-660
apple juice, beta-sitosterol, byproducts, ciders, feed formulation, fructose, glucose, hexane, industrial wastes, ingredients, juice industry, lipophilicity, oligosaccharides, polysaccharides, racing pigeons, sewage, total solids, ultrafiltration, wastewater
Retentate is a by-product of the concentrate apple juice industry, resultant from clarification through an ultrafiltration process. It has a liquid to sludgy appearance, with 8% of total solids content, usually discarded as industrial waste, conveyed as wastewater directly to the sewage plant. However, its origin and expected composition may allow to define its use as a source of valuable compounds as well as its application in food and feed. The present work shows that retentate is very rich in carbohydrates, namely 40% fructose (dry weight), glucose (8%), oligosaccharides (5%), and polysaccharides (3%). It is also rich in protein (8%) and an available and inexpensive source of β-sitosterol (0.6%). This was the major sterol identified, accounting for 21% of total lipophilic compounds recovered by n-hexane. The retentate suspension was successfully used as nutritive medium for production of cider by a microbrewery and the protein-rich water insoluble material (28% of protein) was successfully used in feed formulations for racing pigeons.