Thermal properties of maize masa and tortillas with different components from maize grains, and additives G. Ara ´mbula-Villa a, * , E. Gutie ´rrez-A ´ rias a , E. Moreno-Martı ´nez b a Centro de Investigacio ´ n y de Estudios Avanzados del I.P.N., Unidad Quere ´taro, Libramiento Norponiente # 2000, Fraccionamiento Real de Juriquilla, 76230, Juriquilla, Qro, Me ´xico, Apdo, Postal 1-798, Mexico b Facultad de Estudios Superiores, Cuautitla ´ n, UNAM, Cuautitla ´ n, Izcalli. Edo. de Me ´ xico, Mexico Received 3 March 2006; received in revised form 4 May 2006; accepted 5 May 2006 Available online 23 May 2006 Abstract The thermal properties of wet nixtamalized masa are important during the cooking phase of the tortilla production process. These properties are unique for each material and are affected by the chemical composition and additives supplemented. In this study, effects of pericarp and non-polar lipids extracted from maize grain, and xanthan gum added to traditional wet nixtamalized masa, were exam- ined for thermal diffusivity, conductivity and effusivity, heat capacity, gelatinization temperatures and enthalpy. Components and addi- tives added separately to wet masa were: 1.5%, 3%, 4.5% and 6% (w/w, db) of maize pericarp; 0.5%, 1% and 2% (w/w, db) of non-polar lipids; and 0%, 0.1%, 0.2% and 0.3% (w/w, db) of xanthan gum. The results were compared with those of wet masa and tortillas without additives. Based on results, the best thermal properties were obtained from tortillas of nixtamalized maize masa supplemented with 4.5% (w/w, db) pericarp, or with 0.5% (w/w, db) non-polar lipids, or with 0.1% (w/w, db) xanthan gum. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Maize tortillas; Nixtamalization; Pericarp; Lipids; Xanthan 1. Introduction Maize tortillas are produced from either traditionally milled nixtamal (wet masa) or dehydrated masa flour (MINSA, 2000). Both processes include the following steps: production of the nixtamal, elaboration of the masa, shaping and baking of the tortillas (Serna-Saldı ´var, Go ´ mez, & Rooney, 1990). Many varieties of maize grain with different characteristics of hardness, color, and chem- ical composition can be used to produce the nixtamal and the masa. The nixtamalized masa, produced from milled nixtamal, has different thermal characteristics, and requires varying amounts of heat during the cooking process. To produce adequately cooked tortillas, it is common for the tortilla producer to manually regulate the comal tempera- tures (heat flux) to process each batch. Research has already been conducted on the effects of supplementing the maize grain with pericarp and lipids as well as chemical additives such as CMC, arabic, xanthan, guar gum, and lime (Ca(OH) 2 ) documenting changes in physicochemical, rheological and textural characteristics of the nixtamalized masa and the resulting tortillas, and on their shelf life (Ara ´mbula, Gonza ´lez-Herna ´ndez, Mor- eno, & Ordorica, 2002; Ara ´mbula, Gonza ´lez-Herna ´ndez, & Ordorica, 2001; Ara ´mbula, Mauricio, Figueroa, Gonza ´- lez-Herna ´ndez, & Ordorica, 1999; Campas-Baypoli, Rosas- Burgos, Torres-Cha ´vez, Ramı ´rez-Wong, & Serna-Saldı ´var, 1999; Martı ´nez-Bustos et al., 2001; Nun ˜ ez-Santiago, Santoyo, Bello-Perez, & Santoyo-Gutierrez, 2003; Rodrı ´- guez et al., 1995; Ward & Andon, 1993; Yau, Waniska, & Rooney, 1994). In so far as thermal properties, Alvarado 0260-8774/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2006.05.004 Abbreviations: DM, dehydrated masa; w/w, weight/weight; a, thermal diffusivity; e, thermal effusivity; K, thermal conductivity; C p , heat capacity; DH, gelatinization enthalpy; T o , onset temperature; T p , peak temperature; T e , ending temperature. * Corresponding author. Tel.: +52 442 4414901; fax: +52 442 4414938. E-mail address: garambula@qro.cinvestav.mx (G. Ara ´mbula-Villa). www.elsevier.com/locate/jfoodeng Journal of Food Engineering 80 (2007) 55–60