Effects of guar gum and xanthan gum additions on physical and rheological properties of cationic tapioca starch

Abstract

The gelatinization of cationic tapioca starch embedded in gum matrices was investigated by using a Rapid Visco-Analyzer (RVA), differential scanning calorimeter (DSC), scanning electron microscope (SEM), and rheometer. In addition, swelling power and solubility indices were measured. Xanthan and guar gum increased the RVA peak viscosity of cationic tapioca starch during pasting synergistically in different ways. Guar gum was more effective than xanthan gum in terms of increasing peak viscosity due to its ability to increase the swelling power and solubility index. Both xanthan gum and guar gum induced association between the gelatinized granules probably due to bridging. Association was much more extensive with xanthan. DSC studies showed that the presence of gums influenced the gelatinization characteristics of starch significantly by increasing the onset gelatinization temperature and decreasing the gelatinization enthalpy. Dynamic rheological measurement showed a strong interaction occurred in the cationic tapioca starch–xanthan gum mixture resulting in a decrease in the loss tangent (tan δ) as compared with guar gum addition or starch alone. The ionic interaction of gums and starch was found to play an important role in the gelatinization characteristics of the mixtures and also rheological properties of the pastes.

Introduction

Hydrocolloids (gums) are used in starch-based products to improve stability, modify texture, facilitate processing, reduce costs, control moisture and show a variety of gelatinization and rheological properties (Krüger et al., 2003, Rojas et al., 1999, Shi and BeMiller, 2002, Sudhakar et al., 1996). The use of such combinations was found in food products such as bakery and cereal products, fruit fillings, sauces, frozen foods, and confectionary products (Ward and Andon, 2002, Wei et al., 2001).

Hydrocolloids have been shown to influence the gelatinization of starches. It is well known that addition of hydrocolloids to starch suspensions causes a synergistic increase in viscosity (Alloncle et al., 1989, Liu et al., 2003). There are a few reports about the interactions between starch and gum that discuss the mechanism. Christianson, Hodge, Osborne, and Detroy (1981) found that guar, xanthan, and carboxymethyl cellulose (CMC) gum gave a two-stage increase in viscosity of wheat starch during gelatinization. An initial increase in paste viscosity was attributed to the first stage of swelling and was dependent on media viscosity only. A subsequent increase in final peak viscosity was due to interactions of gums, leached component and swollen starch granules. On the contrary, Shi, & BeMiller (2002) reported that the initial increase in viscosity occurring before pasting of dilute normal maize starch–gum systems was attributed to interactions between certain leached molecules, primarily amyloses, and certain gums, i.e. CMC, gellan, xanthan, guar gum and sodium alginate. Lee, Baek, Cha, Park, and Lim (2002) reported that xanthan gum reduced the paste viscosity of sweet potato starch significantly, possibly through strong network formation with starch, whereas guar gum and alginate increased the viscosity. This result is consistent with those of Shi, & BeMiller (2002), who suggested that the greatly decreased peak viscosity when negatively charged gums were added to potato starch was due to the repulsion between phosphate groups on potato starch and the negative charges on the gum molecules. However, there are few reports on the interaction between gums and modified starch (Abdulmola, Hember, Richardson, & Morris, 1996; Shi, & BeMiller (2002); Tecante & Doublier, 1999) and on the morphology of gelatinization of starch–gum mixtures by using scanning electron microscopy (Jing-ming and Sen-lin, 1990, Mandala et al., 2002).

The aim of this research was to determine the effect of hydrocolloids, i.e. guar gum (neutral gum) and xanthan gum (negatively charged gum), addition at the levels commonly used in food formulations on the pasting and viscoelastic properties of cationic tapioca starch. Cationic starch is used in numerous industrial applications, including as a thickening agent for food products and as an adhesive for paper products. Nevertheless, it is evident here that the selected types of starches and gums play an important role in the understanding of gelatinization mechanism. Recently, several effects were examined to achieve the understanding of mechanisms of starch gelatinization in the presence of gums. However, to the best of our knowledge no study has been published on the interactions of cationic starch and gums.