Optimization of inulin and polydextrose mixtures as sucrose replacers during sugar-free chocolate manufacture – Rheological, microstructure and physical quality characteristics Roger Philip Aidoo a,b,⇑ , Emmanuel Ohene Afoakwa b , Koen Dewettinck a a Department of Food Quality and Food Safety, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium b Department of Nutrition & Food Science, University of Ghana, P.O. Box LG 134, Legon, Accra, Ghana article info Article history: Received 4 August 2013 Received in revised form 25 October 2013 Accepted 28 October 2013 Available online 5 November 2013 Keywords: Chocolate Recipe optimization Mixture design Bulking agent Inulin Polydextrose abstract Inulin and polydextrose have in recent times form basic ingredients in the manufacture of many sugar- free products. However, the applicability and suitability of inulin and polydextrose mixtures as sucrose replacers during manufacture of sugar-free chocolate is yet to be fully understood. This work investigated optimum conditions as well as influences of inulin and polydextrose mixtures as sucrose replacers on rheological properties, microstructure and physical qualities during manufacture of sugar-free chocolate. Increasing inulin concentrations with simultaneous reduction in polydextrose resulted in consistent increases in the Casson plastic viscosity while that led to decreases in Casson yield stress. Chocolate formu- lated with 100% polydextrose revealed large crystals with dense smaller particles and minimal inter-particle spaces compared to large crystals with more void spaces in chocolates formulated with 100% inulin. Chocolate formulation consisting of 75.3594% polydextrose and 24.6406% inulin was found as the opti- mum concentrations producing the most acceptable rheological and physical quality characteristics. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The applicability and suitability of inulin and polydextrose as bulking agents in sugar-free chocolate manufacture have been re- viewed (Aidoo et al., 2013). Polydextrose and inulin are considered as fibres that do not only increase the bulk consistence of food and its rapid movement through the gastrointestinal, but also helps in preventing constipation and possible colon and rectal cancer. Poly- dextrose, a randomly linked polymer of glucose has similar techno- logical properties as sucrose except for sweetness and inulin is a polymer of various lengths comprising of fructose molecules linked together and ending with a glucose molecule (Burdock and Flamm, 1999; Afoakwa et al., 2007a; Beckett, 2009). Polydextrose, as a commercial available preparation, is pro- duced by the condensation of a melt which consists of approxi- mately 89% D-glucose, 10% sorbitol and 1% citric acid on a weight basis (Colliopoulos et al., 1986). The average degree of polymeriza- tion (DP) of polydextrose is 12 (weight average molecular weight of 2000), although the range of molecular weight is 162 to about 20,000 (Craig et al., 1998; Aidoo et al., 2013). Polydextrose has been successfully incorporated into a wide range of foods including baked goods, beverages, confectionery and frozen desserts and is known to provide the bulk and appropriate textural and mouthfeel qualities which are usually associated with sugar and fat while lacking the sweet taste and caloric value connected with those con- ventional food ingredients (Lauridsen, 2004). Inulin is a mixture of oligo- and polysaccharides, which are composed of fructose units connected by b-(2–1) links. The exten- sive use of inulin in the food industry is based on its nutritional and technological properties. Inulin is of interest for the development of healthy products because it simultaneously responds to a vari- ety of consumer demands: it is fibre-enriched, prebiotic, low fat, and low sugar. As a dietary fibre, inulin passes through the diges- tive tract largely undigested. In the colon it acts as a prebiotic be- cause it is selectively fermented by the beneficial flora, stimulates their growth, and reinforces its action against putrefactive micro- organisms (Roberfroid et al., 1998). Inulin can be highly branched or linear depending on the source. The more branched the poly- mers, the more soluble they will become (up to 230 g in 100 g of water), but at the same time offering slightly less viscosity than the linear ones. Inulin and polydextrose have often formed the basis for most researches for use as bulking agents in the production of sugar-free chocolates (Farzanmehr and Abbasi, 2009; Shah et al., 2010; Palazzo et al., 2011). Farzanmehr and Abbasi (2009) evaluated the effects of inulin, polydextrose and maltodextrin as bulking 0260-8774/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jfoodeng.2013.10.036 ⇑ Corresponding author at: Department of Food Quality and Food Safety, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium. Tel.: +32 324 998 90549/+233 509 668676. E-mail addresses: roger.aidoo@UGent.be, pphilipaidoo150@hotmail.com (R.P. Aidoo). Journal of Food Engineering 126 (2014) 35–42 Contents lists available at ScienceDirect Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng