Food Research International 40 (2007) 239–248 www.elsevier.com/locate/foodres 0963-9969/$ - see front matter  2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2006.10.013 Thermal and rheological properties of tapioca starch and xyloglucan mixtures in the presence of sucrose Rungnaphar Pongsawatmanit ¤ , Theeranan Temsiripong, Thongchai Suwonsichon Department of Product Development, Faculty of Agro-Industry, Kasetsart University, 50 Phaholyothin Road, Chatuchak, Bangkok 10900, Thailand Received 1 June 2006; accepted 23 October 2006 Abstract The inXuence of sucrose on thermal and rheological properties of tapioca starch (TS)–tamarind seed xyloglucan (XG) mixtures was investigated. Rapid visco-analysis proWles of 5% w/w TS/XG dispersions at diVerent mixing ratios revealed that peak and Wnal viscosities increased with increasing sucrose and XG contents. Loss tangent of each mixing ratio of TS/XG pastes determined from dynamic rheom- etry exhibited a lower value with increasing sucrose, suggesting solid-like properties contributed from the dissolved sucrose in the systems. Gelatinization temperatures of 25% w/w TS/XG at mixing ratios of 10/0 and 9/1 increased with increasing sucrose content whereas the gelatinization enthalpy of pastes increased in the presence of high sucrose concentration. Sucrose increased the stiVness and hardness of the 25% w/w TS/XG gels (mixing ratios of 10/0, 9.5/0.5 and 9/1) from the compression test. These results suggest that sucrose delays the gelatinization of TS and XG mixtures and strengthens the gels by increasing the elastic component.  2006 Elsevier Ltd. All rights reserved. Keywords: Sucrose; Tapioca starch; Xyloglucan; Gelatinization; Rheological properties 1. Introduction Starch is one of the most important polysaccharides as a raw material or as a food additive in food systems in terms of nutritional qualities or functional properties. Starch is a biopolymer and deWnes as a homopolymer consisting only one monomer, D-glucose (Friedman, 1995). In general, native starches are packed in granules. The characteristics of starch granular swelling, gelatinization and pasting are the important functionalities of the starch as an ingredient in food systems for controlling rheological properties of foods (Nishinari, Zhang, & Ikeda, 2000). Non-starch polysaccharides or hydrocolloids have been widely used in the food industry to improve moisture retention and to maintain overall quality during distribu- tion and storage by controlling rheological and textural properties of foods. When a starch/hydrocolloid mixture is used as a texture modiWer, understanding of its rheological and thermal properties is important. Thus, various studies on rheological and thermal properties of mixtures between starches and hydrocolloids have been reported (Christianson, Hodge, Osborne, & Detroy, 1981; Sudha- kar, Singhal, & Kulkarni, 1995; Temsiripong, Pon- gsawatmanit, Ikeda, & Nishinari, 2005; Yoshimura, Takaya, & Nishinari, 1999). The extent of crystalline parts in starch granule swelling or melting during gelatinization is inXuenced by the presence of hydrocolloids and syner- gistic interactions between hydrocolloids and starch (Shi & BeMiller, 2002). In general, the viscosity of the mixed system is greatly higher than the starch alone since most biopolymers are strongly hydrophilic and compete with the starch for water (Christianson et al., 1981; Funami et al., 2005). In terms of storage, syneresis of the starch can be lower during cold storage by mixing with hydrocolloids such as the systems of corn starch and konjac-glucoman- nan or corn starch and xyloglucan (Yoshimura, Takaya, & Nishinari, 1998, 1999). * Corresponding author. Tel.: +66 2 562 5008; fax: + 66 2 562 5005. E-mail address: fagiruw@ku.ac.th (R. Pongsawatmanit).