Chemical composition

Chemical composition of guar gum and its hydrolytic derivatives were estimated according to standard operating method (AACC 2000). The moisture content (method no. 44-15A) was analyzed gravimetrically by drying the samples in an air forced draft oven (MEMMERT Mod. 1430) at a temperature of 105 ± 5 °C till a constant weight of the dried material is attained. Protein estimation (no. 46-10) was done by Kjeldahl’s method and fat content (no. 30-10) was estimated by using soxhlet extraction with hexane (b.p. 65–70 °C). The ash content (no. 08-01) was determined by heating the sample in a muffle furnace at 550 °C for 5 h followed by cooling and weighing. The fiber content (no. 32-10) was calculated by placing the digested samples in a muffle furnace maintained for 3–5 h at temperature of 550–650 °C till grey or white ash was obtained. Galactose and mannose content of guar gum fractions were estimated with some modifications (Jahanbin et al. 2012). 10 mg pure freeze-dried gum was hydrolyzed by heating at 120 °C (Memmert 100 universal bench, Germany) for 3 h with 1 mL of 2 M trifluoroacetic acid (TFA, CF₃COOH) in a sealed tube. Excess acid was removed by flash evaporation on a water bath at a temperature of 40 °C and co-distilled with three times of water. The hydrolyzed products were reduced with NaBH₄ (50 mg) and filtered through a 0.45 µm filter, and 20 µL of the sample was injected into the HPLC column. A Perkin Elmer Shimadzu HPLC unit and Rezex RCM-Monosaccharide Ca²⁺, Phenomenex column was used to carry out the analysis. HPLC grade water was used as mobile phase (isocratic) at a flow rate of 0.6 mL/min. A refractive-index detector (Gradient LC) was used and the column oven temperature was 80 °C. Monosaccharides were identified by comparing their retention times with the standard sugars. They were quantified according to their percentage area, obtained by integration of the peaks.