Waste water of various boiled legumes as potential of radical scavenging agents

Abstract

Peanut, soybean and chickpea important source of macronutrients and considered as important foodstuff in Malaysia. Boiled legumes are usually sold on by hawker on street. The water used for boiling the legumes is commonly thrown away without considering the radical scavenging potential of this so-called waste. Besides, there is lacking of awareness among the public about its nutritional benefits as part of sustainable food production aimed towards food security and nutrition. Furthermore, food antioxidants might play a significant role as physiological and dietary antioxidants which also could be a substitute for synthetic antioxidants and preservatives. Hence, this study aimed to evaluate the radical scavenging activity of the waste water from the three types of boiled legumes. The legumes were boiled in hot water and the waste water were collected. In this study, the waste water is converted into powder by means of freeze-drying technique. Radical scavenging activity was investigated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay, while its phenolic and flavonoid contents were determined using Folin-Ciocalteu assay and aluminum chloride colorimetric assay. The waste water of peanut showed the highest percentage of DPPH inhibition at 85.03±6.91%, followed by chickpea and soybean waste water at 79.89±3.69% and 69.10±6.19%, respectively. Furthermore, the waste water of peanut also showed the lowest IC50 value of 0.503±0.05 mg/mL, followed by soybean and chickpea of 0.554±0.01 mg/mL and 0.697±0.04 mg/mL. On a side note, peanut waste water extract showed the highest phenolic and flavonoid contents which are 1.877±0.36 mg GAE/g and 0.736±0.01 mg CE/g, respectively, whereas chickpea showed the lowest content of both which are 0.519±0.01 mg GAE/g and 0.227±0.01 mg CE/g, respectively. As conclusion, the waste water of boiled legumes is worth to be further investigated on their radical scavenging activity using other assays and could be potentially developed into functional foods.