Moisture sorption properties of freeze-dried araza (Eugenia stipitata Mc Vaugh) powder: Effect on physicochemical and thermodynamic properties

Abstract

BACKGROUND: Araza, a flavorsome berry rich in antigenotoxic and antimutagenic antioxidants (phenolics/carotenoids/flavonoids/ascorbic acid) could be used for preparing functional powdered instant-beverages. Moisture sorption can cause quality problems therefore a thorough analysis of powder sorption properties is required. OBJECTIVE: To study freeze-dried araza moisture sorption behavior using maltodextrin or Arabic-gum as drying-aids and its effect on isosteric-sorption-heat, differential-entropy, mechanism controlling moisture-sorption, color, solubility and antioxidant content/activity. METHODS: To determine araza/maltodextrin and araza/Arabic-gum moisture-sorption capacities and their effect on powders physicochemical properties, samples were exposed to relative humidities ranging 11-76 and 10/20/40°C until reaching equilibrium. Changes in equilibrium water content (Wc), cold water solubility, antioxidant (polyphenols, flavonoids, carotenoids and ascorbic acid) concentration and activity were recorded. RESULTS: GAB model satisfactorily predicted Wm; the samples monolayer-moisture concentrations were lower than 0.1 kg H2O (kg dried matter)-1 indicating good powder stability. Thermodynamic properties/Wc relationships and the sorption process mechanism were determined. At 10/20°C araza/maltodextrin had better color/solubility, higher total polyphenols/carotenoids/flavonoids and lower ascorbic acid contents than araza/Arabic-gum, however, antioxidant activities were similar. Temperature/water activity (aw) combinations for optimum color, solubility, antioxidant content/activity were 10°C/aw ≤0.11 (araza/Arabic-gum) and 10°C/aw ≤0.23 (araza/maltodextrin).