The impact of moisture sorption properties on the color and bioactives concentrations of black currant-yerba mate instant drinks

JULIANA ORJUELA PALACIO; LANARI MARIA CECILIA

JOURNAL OF BERRY RESEARCH

IOS Press

Año: 2016 vol. 6 p. 303 - 319

BACKGROUND:Black currant (BC) and yerba mate (YM) have highcontents of polyphenolic antioxidants beneficial for health. Obtainingfreeze-dried BC/YM instant drinks can be a means for providing their advantagesto consumers. However, their high sugar contents make them very hygroscopic causingundesirable changes in color and bioactives concentration. OBJECTIVE: To solve this problem it is necessary to determine the powder´s sorptionproperties and the temperature/relative humidity?s (RH) influence on their colorand polyphenol, ascorbic acid and anthocyanins´s concentrations. METHODS:We analyzed the sorption isotherms of freeze-dried YMI/BC/maltodextrin/sugarpowder at 10/20/40ºC and compared them with those from YM/maltodextrin. RESULTS: Of all models tested (Caurie, GAB, Halsey, Oswin) GABwas the best. Monolayer moisture values (Wm) were ≤0.1 kg H2O (kg d.m)-1indicating good stability. Due to its higher sugar content, BC/YM powders weremore hygroscopic and with higher exothermic isosteric sorption heat (Qst)than YM powders. Qst and differential entropy decreased exponentiallywith increasing moisture levels. Within the experimental conditions, isokinetictheory indicated that the whole sorption process was enthalpy controlled. Temperatureand RH strongly modified BC/YM´s color and ascorbic acid and monomericanthocyanins concentrations. At all temperatures, optimum levels of theseproperties required RH≤33%. To achieve maximum physicochemical quality andstability the powder?s moisture content must be ≤ Wm, in this case, RH droppedto 9% (10°C)and 11.3% (20°C/40°C).Keywords: Black currant; Yerba mate; sorption properties,anthocyanins, ascorbic acid, color.