Abstract:
Nutritional compounds in yams may leach out to the cooking water
under most traditional domestic cooking methods. Finding alternative uses of
these waste waters without discarding, can maximize the usage and importance of
these yams. This study aimed to quantify the bioactive compounds and determine
the antioxidant activity in the cooking water collected after boiling of Dioscorea
alata L. tubers under two domestic cooking methods. Raja ala yams were boiled in
water using conventional boiling (CB) and pressure cooking (PC) methods. The
cooking water of both methods were collected and concentrated to obtain the solid
crude product. Aqueous solutions of the crude product of CB and PC samples
were prepared and subjected to qualitative phytochemical analysis. Further, they
were assayed for total phenolic content (TPC), total flavonoid content (TFC), and
total anthocyanin content (TAC). Antioxidant activity of each crude product was
determined and a correlation between the antioxidant activity and TPC, TFC and
TAC of the samples was developed using the Pearson’s correlation method.
Phytochemical screening of CB and PC samples showed the presence of alkaloids,
flavonoids, phenols, saponin, tannins and coumarins and an absence of proteins.
CB showed a significantly higher TPC than that of PC whereas the TFC of PC was
higher than CB. Both methods however, showed no significant difference in TAC
extraction. Antioxidant assays showed higher activity in CB over the PC sample.
A strong correlation was observed between TPC versus DPPH activity (IC50 value)
and TAA of the samples. It can thus be concluded that the wastewater of both
cooking methods contain a significant amount of bioactive compounds, making it
a nutritious source to be further investigated and to be made use for alternate
purposes without discarding it.
