Concentration of beverages by osmotic evaporation: effect on organoleptic properties and antioxidant activity

• Autor(a) principal: Marques, Cátia Marisa Pereira
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/13822
• topic: Osmotic evaporation; Membrane contactors; Beverage concentration; Antioxidant activity; Phenolic content; Ascorbic acid

The concentration of beverages has a great interest because it enables lowering the transportation, storage and packaging costs, as well as theincrease of product’s shelf lifeoriginated by its higher resistance to microbial activity. Membrane processes have been proposed for beverages’ concentration as promising alternatives to the traditional concentration processesdue to the mild operating conditions. In this work, the osmotic evaporation membrane process was used in order to concentrate three different teas and fresh orange juice, as well as evaluating the effect of this process on the organoleptic properties and antioxidant activity.The concentration process was carried out in a hollow fibre membrane contactor. The beverage was circulated through the shell side of the contactorand a concentrated osmotic solution (CaCl25M) was circulated inside the fibres. The flux, the driving force and the mass transfer coefficient were evaluated during the process time. All beverages were concentrated at least threetimes.The concentrated beverages were analysed in terms of their antioxidant activity (DPPH and FRAP methods), total phenolic content (Folin-Ciocalteu method) and colour. Ascorbic acid concentration was measured for the orange juice by 2,6 -dichlorophenolindophenol -xylene extraction method.The results indicate thatthe antioxidant activity and total phenolic content remains constant during the first sixhours of the concentration process, after which a decrease was noticed. Alterations in the beverages colour after the concentration process (7.11<ΔE*I,F<24.32)were observed. Thecontent ofascorbic acid decreases 32.7% during the concentration process.However, these results are not a limitation since the process can be operated in a shorter time, using membrane contactors with highercontact areas.