Optimization of Cornstarch/xanthan Gum Content for Thickening of Cocoa Syrups

Blended cornstarch–xanthan gum systems were optimized for thickening of cocoa syrups. For this purpose the sensory (whole and partial), textural (force of penetration, adhesiveness and stringiness) and rheological properties (flow curves as well as viscosity/time and viscosity/temperature relationships) of cocoa syrups were studied. Flow curves were described by rheological model of Casson, which accounted syrups under study for non-Newtonian, pseudoplastic and thixotropic fluids. Also models of Weltman and Arrhenius were applied for comparison of obtained data. The areas of thixotropy hysteresis loops were also calculated. Obtained data (sensory, textural and rheological) were used as a base for mathematical calculations. The results were presented in the tables to enable their easier understanding. As a result, optimization of thickeners was achieved – the best ranges of cornstarch (0.45–0.49%) as well as xanthan gum (0.15–0.17%) concentrations in cocoa syrups were selected. PRACTICAL APPLICATION The result of this study could be used as a guide for thickening of cocoa syrups by the application of cornstarch–xanthan gum combination, chemically nonmodified thickeners. Mathematical method tried in this study for 4 Corresponding author. TEL: +(48 12) 662-47-74; FAX: +(48 12) 662-47-47; EMAIL: rrsikora@ cyf-kr.edu.pl Journal of Food Quality 30 (2007) 682–702. All Rights Reserved. © 2007, The Author(s) Journal compilation © 2007, Blackwell Publishing 682 optimization of thickeners addition could be useful for optimization of the other thickeners and additives employed for different sauces, syrups, dressings, ketchups, mayonnaises, etc. INTRODUCTION Cocoa syrups are used as additives and decoration of fruit salads, pancakes, ice creams, desserts and cooked rice, enhancing their taste and aesthetic qualities. Different thickeners can be applied for granting the textural, sensory and rheological properties of syrups. In the previous papers, the use of such polysaccharide hydrocolloids as agar, carrageenan, carboxymethyl cellulose and xanthan gum in diversified concentrations for thickening of cocoa syrups was proposed (Sikora et al. 2003a). For stabilization, thickening and textureproviding modified starches, such as acetylated distarch adipate and oxidized starch were also tested (Sikora et al. 2004). Several benefits in controlling texture and sensory properties of foodstuffs, rheology of aqueous solutions of hydrocolloids come from polysaccharide–polysaccharide interactions in their blends. By the use of blends of native starch and xanthan gum, it is possible to obtain food with appropriate features. This kind of blends is an alternative solution as opposed to more expensive and often criticized chemically modified starches (Kulicke et al. 1996). According to Tolstoguzov (2003) thermodynamic compatibility between polysaccharides governs their intermolecular interactions. For example, when starch is concerned, two amylose molecules in aqueous solution tend to form organized structures, because of their good compatibility. As a result retrogradation occurs (Fredriksson et al. 1998), which is not a very desirable phenomenon in food technology. On the other hand, because of imperfect thermodynamic compatibility, retrogradation of amylopectin slows down (Gudmunsson 1994). Amylose and amylopectin in aqueous phases separate because of lack of thermodynamic compatibility between both polysaccharide constituents (Kalichevsky et al. 1986; Lii et al. 2002). Numerous studies on the properties of polysaccharide combinations have been published, because the prediction of any results of polysaccharide blending is difficult. The results of such studies of the polysaccharide blends with starches being one of the component of the blend have been reviewed by Sikora and Kowalski (2006). Authors of the same research group have published many papers on the application of thickening blends in different food systems, e.g., sweet and sour sauces (Sikora et al. 2003c,d; Gibiński et al. 2006a), mayonnaises (Gibiński et al. 2006b) and dessert sauces (Sikora et al. 2006). 683 OPTIMIZED CORNSTARCH/XANTHAN GUM CONTENT IN COCOA SYRUPS