Effect of particle sizes on in-vitro calcium and magnesium binding capacity of prepared dietary fibers Arpathsra Sangnark a , Athapol Noomhorm b, * a Food Science Department, Faculty of Science, Burapha University, Chonburi, 20131, Thailand b School of Environment, Resources and Development, Processing Technology Program, Asian Institute of Technology, Pathumthani, 12120, Thailand Received 22 December 2001; received in revised form 8 April 2002; accepted 8 April 2002 Abstract Microscopic examination showed a change on the surface structure of dietary fibers (DF) from rice straw (RS) and sugarcane bagasse (SB) by alkaline hydrogen peroxide (AHP) treatment. Effect of particle size on in-vitro binding of calcium (Ca) and mag- nesium(Mg)ofAHP-RS,AHP-SBandSolkaFloc 1 900(SF)wereevaluated.TotalboundCaandMgdecreasedwithparticlesize reduction (P < 0.05)foralltypesofDF.CaandMg(82–95%)werereleasedfromAHP-RSandAHP-SBbyacidwashingbutonly 53–60% Mg was removed from SF. There were strong correlations between water holding capacity, oil binding capacity and par- ticledensityandtotalboundCaandMgforallDFsamples. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Alkaline hydrogen peroxide; Dietary fiber; Particle sizes; Mineral binding; Calcium; Magnesium 1. Introduction Lignocellulose materials such as cereal bran or vege- table pulps are sources of dietary fibers (DF). However, these materials are not without negative effects in their application to enhance the dietary quality of foods. When unprocessed lignocellulose materials are added to bakery formulations, the products lose volume after baking and have an unpleasant texture (Dubois, 1978; Titcomb & Juers, 1986). This is attributed to their poor hydration property which restricts their integration into doughorbatter(Gould,Jasberg,Dexter,Hsu,Lewis,& Fahey, 1989). Treatment with alkaline hydrogen perox- ide (AHP) improves the hydration property of unpro- cessed lignocellulose materials (Gould, 1987, 1989), and forwheatstraw,allowsitsapplicationwithoutlosingits baking performance and sensory quality (Jasberg, Gould, & Warner, 1989; Jasberg, Gould, Warner, & Navickis, 1989). The addition of DF into foods has been also asso- ciated with negative impacts on mineral bioavailability, particularly in high-risk population groups. DF can adsorb micronutrients such as calcium (Ca) and mag- nesium (Mg) on their surface, possibly reducing their availability in-vitro (Claye, Iodouraine, & Weber, 1998) or causing a negative mineral balance in-vivo (Nnakwe, Kies, & Fox, 1989). The effects of some factors such as the source of DF (cellulose, hemicellulose, pectin, and lignin) and pH of the binding solution on mineral binding capacity of DF have been investigated (Claye, Iodouraine, & Weber, 1996; Claye et al., 1998). Particle size of DF was not found to affect the binding capacity for Ca and Mg in spite of the inverse particle size rela- tionship between surface area and volume. Conse- quently, the adsorption uptake increases (Huang & Dural, 1995). Particle size of DF also was an important factor for food application (Abbott, O’Palka, & Mcguire, 1991). Manufacturers reduce particle size when DF is used as an additive in processed food, in order to improve consumer acceptance (Ebihara & Takeuchi, 1991). In Thailand, sugarcane bagasse (SB) and rice straw (RS) are plentiful waste products from sugar and rice production, respectively. Normally, both waste pro- ducts are used for fertilizer and cattle feed. However, thelargeamountofDFinSBandRS(EL-Masry,1983; Fernandez,Borroto,Rodriguez,&Beltran,1996)makes 0963-9969/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0963-9969(02)00112-6 Food Research International 36 (2003) 91–96 www.elsevier.com/locate/foodres * Corresponding author. Tel.: +66-2524-5476; fax: +66-2524- 6200. E-mail address: athapol@ait.ac.th (A. Noomhorm).