The carbonyl content was determined as previously described by Smith (1967). A dry sample (4 g) of starch was dispersed in distilled water (100 ml) and heated in a boiling water bath for 30 min. The solution was

continuously stirred until the starch was completely gelatinised. The gelatinised samples were kept at 40 °C. The pH value was adjusted to 3.2 with 0.1 M HCl, and 15 ml of a hydroxylamine chloride solution was then added. The hydroxylamine reagent was prepared by dissolving 25 g of reagent grade hydroxylamine chloride in water and adding 100 ml of 0.5 M NaOH; distilled water was then added to reach a final volume of 500 ml. The samples were covered with plastic film and placed in an oven at 38 °C for 4 h, check details and they were then rapidly titrated to a pH value of 3.2 with 0.1 M HCl. The carbonyl content was expressed as the quantity of carbonyl groups per 100 glucose units (CO/100 GU) as calculated by Eq. (1). equation(1) CO/100GU=(Vb-Vs)×M×0.028×100Wwhere Vb is the volume of HCl used for the blank (ml), Vs is the volume of HCl required for the sample (ml) M is the molarity of HCl, and W is the sample weight (d.b). The carboxyl content was determined according to the method previously described by Parovuori, Hamunen, Forssell, Autio, and Poutanen (1995). A dry sample

(5 g) of starch was dispersed in distilled water (25 ml). The dispersions were stirred for 30 min and then centrifuged. Quisqualic acid The residue was washed with distilled water, and 300 ml of distilled water was then added to the residue. The dispersion was heated in a boiling water bath with selleckchem continuous stirring for 30 min until the starch was completely gelatinised. While still hot, the samples were titrated to a pH value of 8.2 with 0.01 M NaOH. The carboxyl content was expressed as the quantity of carboxyl groups per 100 glucose units (COOH/100 GU) as calculated by Eq. (2).

equation(2) COOH/100GU=(Vs-Vb)×M×0.045×100Wwhere Vs is the volume of NaOH required for the sample (ml), Vb is the volume of NaOH used to test the blank (ml), M is the molarity of NaOH, and W is the sample weight (d.b). The swelling power and solubility of the starches were determined as described by Leach, McCowen, and Schoch (1959). Samples (1.0 g) were mixed with 50 ml of distilled water in centrifuge tubes. The suspensions were heated at 90 °C for 30 min. The gelatinised samples were then cooled to room temperature and centrifuged at 1000g for 20 min. The supernatants were dried at 110 °C until a constant weight was achieved so that the soluble fraction could be quantified. The solubility was expressed as the percentage of the dried solid weight based on the dry sample weight. The swelling power was represented as the ratio of wet sediment weight to initial dry sample weight (deducting the amount of soluble starch).