Highly purified sugar concentrate from a residue of citrus pigments recovery process

Pigmented orange pulp wash (PW), a byproduct of citrus processing, was already studied to obtain anthocyanins and hydroxycinnamates using adsorption resins. The residue of such process was further investigated to obtain a purified sugar concentrate applying a series of resin adsorptions and membrane techniques. The final product and the intermediates were characterized by chemical and microbiological analyses. The results have shown that anthocyanins, limonoids, flavanones and hydroxycinnamates were absent in the starting material because totally removed by the treatment with the neutral polystyrene-divinylbenzene (PS-DVB) resin used to recover the pigments; the acidity was strongly reduced through a weakly basic ion-exchange matrix while the ultrafiltration (UF) process stabilized the product by removal of enzymes and microorganisms. Eighty percent of the water was eliminated by a reverse osmosis (RO) treatment, increasing the sugar concentration by four times. The final product (28 Brix) contained about 250 g/l of sugars (glucose, fructose and sucrose), 9 g/l of citric acid and 1 g/l of pectins. The concentrate, obtained from a residue that otherwise must be disposed, was a transparent liquid of slight amber color with a very low microbial count and could easily find application as a natural sweetener in food and beverage industries.