Optimization of microwave assisted extraction of mucilage from garden cress seeds and its characterization

The mucilage extracted from the cress seed can be of tremendous importance owing to its functional properties. However, the longer extraction time, along with lower yield, poses hindrance in its commercial application. The conventional extraction method is based on soaking seeds for at least 12 h, with a lower yield. The present study is based on extraction carried out using microwave radiation to reduce extraction time. Factors such as microwave powder density (1 to 5 W/g), pH (3 to 9) for extraction, and treatment time (1.5 to 8 min) were optimized to get maximum mucilage yield. The optimized condition was achieved at power density of 3.14 W/g, 7.519 pH, and 8 min with yield of 13.4 %. Besides, the kinetic study was carried out at optimized conditions. The mucilage was characterized by physical and functional properties such as proximate content, differential scanning calorimetry, scanning electron microscopy, isothermal properties, and rheological characteristics. The mucilage powder exhibited high water and oil-holding capacity, poor foaming ability, and high emulsion-forming capacity. The powder also showed a crystalline nature and rapidly absorbed moisture above 50 % relative humidity. The rheological characterization suggests that aqueous solution of the mucilage is viscoelastic liquid with initial yield stress.