Determination of physicochemical, nutritional, hydration and functional properties of commercial Psyllium husk

Abstract

Psyllium husk, derived from the seeds of Plantago ovata, has attracted substantial scientific interest in recent years due to its notable nutritional composition, functional properties, gelforming ability, and potential health-promoting effects. This study aimed to provide a simplified and practical characterisation of commercial Psyllium husk to support its application in developing or modifying food products. The present study was carried out as the first investigation in Sri Lanka to examine the physicochemical, nutritional, hydration properties, and some functional properties of commercial Psyllium husk. According to the research methodology, physicochemical properties (colour analysis, whiteness, bulk density, and pH) and hydration properties (water holding capacity, water retention capacity, swelling capacity, fat absorption capacity, water solubility index, and hygroscopicity) were determined. Functional properties, which are antioxidant content, volatile compounds, and functional groups, were determined by DPPH assay, SPME-GC-MS technique, and FT-IR analysis, respectively. Nutritional compositional analysis was done using AOAC official methods. The average whiteness of dry Psyllium husk was 64.86±0.61, while the average L*, a*, and b* colour values were 72.06±0.65, 3.22±0.57, and 21.07±0.65, respectively. The bulk density and pH of the Psyllium husk sample were 504.33±7.51 gL−1 and 5.37±0.05, respectively. The proximate analysis indicated that carbohydrates constituted 78.43% of Psyllium husk, with moisture at 12.59±0.30%, total fat 2.23±0.16%, crude protein 1.24±0.03%, total ash 2.12±0.12%, dilute HCl acid-insoluble ash 0.23±0.02%, and crude fibre 3.15±0.08%. The hydration properties of Psyllium husk included water holding capacity of 21.73±0.86 g/g, water retention capacity of 9.44±0.64 g/g, swelling capacity of 20.43±0.94 ml/g, water solubility index of 7.13±0.50%, fat absorption capacity of 1.05±0.01 g/g, and hygroscopicity of 8.23±0.65% after 5 days and 9.45±0.87% after 7 days. The antioxidant content of Psyllium husk was 26.16±0.19 μg ml−1. The total number of volatile compounds detected was 13. The SPME technique mainly isolated long-chain n-alkyl compounds and caryophyllene. Labelled peaks of the FT-IR spectrum confirmed that Psyllium husk contains complex carbohydrates, including hemicellulose, cellulose, uronic acid residues, and mainly arabinoxylans. This study clearly shows that commercial Psyllium husk has valuable nutritional, hydration properties, and functional compounds, making it a highly suitable ingredient for developing functional and health-promoting food products.