Abstract

AYALA APONTE, ALFREDO; SERNA COCK, LILIANA  and  RODRIGUEZ DE LA PAVA, GLORIA. MOISTURE ADSORPTION ISOTHERMS IN YELLOW PITAHAYA (Selenicereusmegalanthus). Dyna rev.fac.nac.minas [online]. 2011, vol.78, n.170, pp.7-14. ISSN 0012-7353.

Moisture adsorption isotherms for yellow pitahaya fruits were studied at 15, 25, and 35 °C using the gravimetric method for a 0.111-0.901 water activity range. Experimental values were adjusted by using the GAB, BET, Henderson, Smith, Caurie, and Peleg models. The isosteric heat of adsorption (Qst) was determined using the Clausius-Clapeyron equation. The results showed that yellow pitahaya fruits exhibit type III adsorption isotherms and that the equilibrium moisture content (EMC) is temperature-dependent. For the same water activity value, the EMC decreased when temperature increased. The GAB model presented the best fitto the experimental values. The Qst dropped from 57.154 to 45.79 kJ/mol when the EMC increased from 0.05 to 0.40 g water/g dry matter, respectively. These results are important for establishing the best storage conditions for dehydrated pitahaya fruits as well as for shelf-life prediction and the design of packaging materials.

Keywords : Yellow pitahaya; adsorption isotherms; isosteric heat of adsorption.

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