Influence of trona (sodium sesquicarbonate) concentrations and storage period on the physicochemical properties, antinutrients, micronutrients and sensory qualities of dried okra (Abelmoschus esculentus L.) powder

Abstract

The potential of trona (sodium sesquicarbonate) as a natural preservative in dried-okra powder was examined in this study. Fresh okra was dried at 55 °C and then ground to powder. It was mixed with ground trona at 2%, 4%, 6% and 10% concentrations and then stored at ambient temperature for six weeks. The functional, nutritional, antinutritional, physicochemical and sensory properties of the okra powder samples were examined every two weeks. Drying resulted in significant (p < 0.05) loss of moisture (94%), pH, flavonoids (34%), tannin (4.63%), phytate (32.70%), oxalate (24.49%), β-carotene (43%) and ascorbic acid (53%) content of the okra. Color loss occurred in trona-treated samples and during storage but it was better retained at low trona concentration. Moisture (5.28–6.03%), viscosity (96.30–124.55 mpa.s) and pH (5.64–8.30) of the okra powder increased with increasing trona concentration and then decreased during storage. Trona mostly decreased the packed bulk density (0.84–0.72 g/mL), water absorption (686.28–423.22%), oil absorption capacity (188.07–124.54%) and water solubility index (12.12–10.27%) of the okra but they were mostly stable during storage. Trona decreased the flavonoids, tannin, calcium, potassium and phosphorus of the okra powder while the phytate, oxalate and sodium mostly increased. Antinutrients and minerals showed slight reduction during the storage period. Most of the trona-treated okra samples showed lower β-carotene and ascorbic acid content which were better retained during storage than in the control. All the soups prepared from fresh and stored okra powders were acceptable to the panelists. However, freshly-dried okra with 2–4% trona and okra stored with 4–6% trona for six weeks are recommended for preparing nutritious soups with high acceptability.