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Abstract(s)
In this study the desorption isotherms of fresh pears were investigated at 30 ºC for fruits of the varieties Amêndoa, Amorim, Carapinheira Branca and S. Bartolomeu, all original from Portugal. This value of temperature was established to represent the summer average daily temperatures in Portugal, where the solar dried of pears is carried out. From the results obtained it was possible to verify that the behaviour of the equilibrium moisture content against the corresponding water activity is very similar for the four varieties of pears, and is of type III according to the Brunauer et al. (1940) classification of isotherms, very characteristic of products rich in carbohydrates (Vásquez-Uña, 2001; Rizvi, 1986).
The experimental data were fitted to the Guggenheim-Anderson-deBoer (GAB), Halsey, Hendersen and Oswin models found in literature (Viswanathan, 2003). The performance of these models was evaluated by comparing the coefficient of correlation (R), the residuals of moisture content and the prediction capabilities.
From the results obtained it was possible to conclude that the Oswin model is less appropriate for describing the process at study, and that the Chen and Halsey models are also not very adequate. The Henderson and GAB models, and this last in particular, was the one that allowed the best prediction capabilities for the isotherms of the varieties of pears studied.
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Keywords
Solar drying sorption isotherms water activity
Citation
Barroca MJ, Guiné RPF, Ferreira DMS, Gonçalves FM. (2005) Sorption isotherms of Portuguese varieties of pears. Livro de resumos e CD-Rom das Actas do 7º Encontro de Química dos Alimentos, P3.8, 7 pag., Viseu.