RESEARCH ARTICLE Gellan gum/cassava starch mixtures in water systems and in milk systems Rafael Coronato 1 , Eliza A. R. Biasutti 2 , Carlos W. P. Carvalho 3 and Maria V. E. Grossmann 1 1 Universidade Estadual de Londrina, Departamento de Cie ˆncia e Tecnologia de Alimentos, Londrina, PR, Brazil 2 Universidade Estadual de Campinas, Departamento de Tecnologia de Alimentos, Campinas, SP, Brazil 3 Embrapa Agroindustria de Alimentos, Rio de Janeiro, Brazil Cassava starch is an important ingredient in various foods. However, when processed, it develops some properties that are unsuitable for many industrial applications, such as unstable viscosity and excessive cohesiveness. To reduce those disadvantages, one alterna- tive is a mixture of starch with hydrocolloids. The aim of this study was to evaluate the effect of 0:05, 0.1, 0.2, or 0.3% w/v gellan gum on the physical properties of pastes and gels of cassava starch in water and in milk systems. Differential scanning calorimetry (DSC), pasting properties, the texture profile, and the microstructure of gels were studied. The addition of gellan gum dispersions to the water system (WS) and the milk system (MS) gave rise to pastes with higher viscosity and, in the case of MS, with lower thermal and shear stability (higher breakdown). The addition of gellan gum had a greater textural effect on the MS, in which the addition of gellan at concentrations of 0.1 and 0.3% increased adhesiveness and decreased springiness of gels. Microscopy revealed a more uniform gel structure in the MS compared with the WS. Starch gelatinization temperatures were higher in MS than in WS. Received: July 8, 2011 Revised: November 29, 2011 Accepted: December 2, 2011 Keywords: Cassava starch / Gellan gum / Microscopy / Paste properties / Texture profile 1 Introduction Cassava starch is used in the food industry in snacks, pastas, desserts [1], frozen foods (fruit pulp, soups, sauces, and creams) [2], and as a thickening and gelling agent [3]. Despite its importance, the use of cassava starch in products such as sauces, puddings, mayonnaise, and fillings is limited because it forms pastes with high cohesive- ness and long texture with a low sensory acceptability [4]. Cassava starch pastes are characterized by a high viscosity and poor stability to temperature and shear forces. For most foods, viscosity decreases during cooking and the cohesive texture (which affects the appearance) are unpleasant [5]. A technique that is used to alleviate this limitation is the mixture with hydrocolloids. Hydrocolloids, or gums, are polysaccharides that solu- bilize or disperse in water and are added to foods as thickeners, controllers or texture modifiers, as well as stabilizing agents. Gellan gum is a relatively new gum that is capable of forming gels in the presence of cations, even at low concentrations. The gel formation mechanism has not been fully elucidated, but it is believed to occur as follows. Initially, gellan molecules are present in a disor- dered spiral form. When heated in an aqueous solution, followed by cooling, the molecules become ordered in a double helix conformation held together by hydrogen bonds or Van der Waals forces [6]. Cations interact with the carboxyl terminals of the hydrocolloid [7] and block electrostatic repulsion between the double helices of the gellan gum, thus increasing thermal stability [6]. Correspondence: Dr. Maria V. E. Grossmann, Universidade Estadual de Londrina, Departamento de Cie ˆncia e Tecnologia de Alimentos, Rod. Celso Garcia Cid Km 380, 86051-990 Londrina, PR, Brazil E-mail: victoria@uel.br Fax: þ55-43-33714080 Abbreviations: BD, breakdown; MS, milk system; MV, maximum viscosity; MVT, maximum viscosity temperature; PS, paste stability; PT, paste temperature; T f , final temperature; T p , peak temperature; TPA, texture profile analyses; V50, final viscosity at 508C; WS, water system DOI 10.1002/star.201100102 Starch/Sta ¨ rke 2012, 64, 359–366 359 ß 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.starch-journal.com