EFFECT OF DIFFERENT COOKING METHODS ON THE BIOACCESSIBILITY OF POLYPHENOLS AND ANTIOXIDANT CAPACITIES OF PAKWAN BAN (SAUROPUS ANDROGYNUS)

Abstract

This study was aimed to assess the effect of different cooking methods on the amounts of phytochemical compounds and antioxidant capacities of sweet leaf (Sauropus androgynus) before and during in vitro simulated gastrointestinal digestion. The optimum cooking time of each cooking method was prior selected according to the total phenolic compounds, the ferric-reductase antioxidant power (FRAP) activity, the color characteristics, the hardness, and the texture preference of cooked sweet leaf samples. Consequently, the sweet leaf samples cooked by boiling for 5 mins or microwaving at 800 watts for 90 sec were compared with raw sweet leaf. The results showed that the microwave cooking significantly demonstrated the higher antioxidant capacities (both FRAP and DPPH radical scavenging activities) of sweet leaf samples than the raw and the boiling methods (P < 0.05). The boiling and microwave cooking methods significantly increased the bioaccessibility of phytochemicals: total phenolic compounds, total flavonoids, beta-carotene contents, and the antioxidant capacities (FRAP and DPPH assay) of sweet leaf than those found in the raw leaves (P < 0.05). Furthermore, the addition of 10% palm oil (v/w) during all cooking methods (raw, boiling, and microwave cooking) significantly increased the bioaccessibility of total phenolic compounds, beta-carotene content, and the antioxidant capacities (FRAP and DPPH assay) compared with those without palm oil addition, respectively (P < 0.05). In conclusion, microwaving and addition of palm oil during cooking exhibited the increased bioaccessibility of total phenolic compounds, beta-carotene content and antioxidant capacities than boiled and raw sweet leaf.