Physicochemical, thermal and sorption properties of nutritionally differentiated flours and starches María C. Doporto a , Cecilia Dini a , Alicia Mugridge a , Sonia Z. Viña a,b , María A. García a,⇑ a Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA), Facultad Ciencias Exactas Universidad Nacional de La Plata (UNLP) – CONICET La Plata, 47 y 116 S/N°, La Plata B1900AJJ, Buenos Aires, Argentina b Curso Bioquímica y Fitoquímica, Facultad Ciencias Agrarias y Forestales UNLP, Argentina article info Article history: Received 11 January 2012 Received in revised form 22 June 2012 Accepted 21 July 2012 Available online 31 July 2012 Keywords: Flour and starch stability Thermal behavior Physicochemical properties Water sorption process Thermodynamic properties abstract The aims of this work were to analyze physicochemical and thermal properties of ahipa and cassava flours and starches and to determine their water sorption isotherms and thermodynamic properties. Both flours are naturally gluten-free products, obtained by relatively simple procedures (grating or slicing). Ahipa flour gelatinized at lower temperature than cassava, indicating a better aptitude for cooking. Gela- tinization temperatures of flours were higher than those of their starches. Water holding capacity of ahi- pa flours was significantly higher than those of cassava, leading the slicing process the highest values. Sorption isotherms were determined at 10, 20 and 30 °C. Experimental data were satisfactorily fitted using different mathematical models. Thermodynamic parameters associated with water adsorption pro- cess were calculated from GAB model, as well as the monolayer water content. All samples could be con- sidered as products with an acceptable stability. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Many of the developing countries’ economies are greatly reliant on root and tuber (R&T) crops as a source of food, nutrients, and profits. Cassava, one of the most important calories supply in the tropics, is relevant in the agriculture of areas where resources are scarce. Cassava can be considered a traditional R&T crop. On the other hand, the neotropical genus Pachyrhizus DC. (Yam beans) is one of the few legume genera with edible tuberous roots. Pachy- rhizus species could be developed as a new source of non-tradi- tional flour and starch. This genus is native to Southern and Central America and the main cultivated species are: Pachyrhizus tuberosus, the ‘‘Amazonian yam bean’’, grown in Bolivia, Peru, Ecuador, and Brazil; Pachyrhizus erosus, the ‘‘jacatupe’’ or ‘‘Mexican yam bean’’, found in Central America and the Caribbean, and Pachyrhizus ahipa, the ‘‘Andean yam bean’’ or ‘‘ahipa’’ from the An- des of Bolivia and Northern Argentina (Forsyth et al., 2002). Inter- est in Pachyrhizus species use have arose as it is demonstrated by several studies on the subject (Doporto et al., 2011; Leonel et al., 2005; López et al., 2010). Nevertheless, references about ahipa roots industrialization are rather scarce. In order to develop gluten-free breads for celiac patients, a number of alternative flour types to wheat such as corn, cassava, rice, soybean and chickpea flour have been used (Demirkesen et al., 2010). In the same way that cassava, ahipa flour can be con- sidered a nutritionally differentiated product since it is a naturally gluten-free flour (with prolamins content below 0.1 mg/100 g, according to currently available detection methods). Water sorption of foodstuffs is a major subject in different areas of food science and engineering. Sorption isotherms of food prod- ucts provide helpful information for the design, modeling and opti- mization of many operations and technological processes (i.e. drying, aeration). Likewise, the study of water sorption phenome- non allows predicting the stability and quality during packaging and storage of food products. According to Vishwakarma et al. (2011), the adsorption of moisture by foods is a process wherein water molecules progressively and reversibly combine with the food solids via chemical sorption, physical adsorption, and multi- layer condensation. Moisture content at which vapor pressure of water present in food equals that of the surroundings is referred to as equilibrium moisture content (EMC). Moisture sorption iso- therm gives the relationship between EMC and the corresponding water activity at constant temperature. On the other hand, thermodynamic approach relates to the understanding of water equilibrium with its surroundings at cer- tain relative humidity and temperature, water which is unavailable for solvation of solutes and water remaining unfrozen below the normal freezing point. Some thermodynamic functions used in analyzing sorption behavior of biological systems include total heat of sorption, differential heat of sorption, differential entropy, enthalpy–entropy compensation, integral enthalpy and integral 0260-8774/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jfoodeng.2012.07.021 ⇑ Corresponding author. Tel.: +54 221 424 9287; fax: +54 221 425 4853. E-mail address: magarcia@quimica.unlp.edu.ar (M.A. García). Journal of Food Engineering 113 (2012) 569–576 Contents lists available at SciVerse ScienceDirect Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng