Effect of Boiling Times on Polyphenol, Flavonoid, Tannin, Vitamin C and β-carotene contents of African Asparagus (Laccosperma secundiflorum): Their Contribution to Overall Antioxidant Activity

Aims: Laccosperma secundiflorum is a very important rattan species for certain populations in the Ivory Coast. They use the apical meristem in their food and the stems to make various items such as furniture, carpets and baskets etc. However, there is a gap in the study of its nutritional value and its nutritional potential before and after boiling.

Place and Duration of Study: Department of Food Science and Technology (UFR-STA), University nangui abrogoua, between December 2019 and November 2020.

Methodology: African asparagus was boiled for 5, 10 and 15 minutes respectively. The effect of boiling on the total polyphenols, flavonoids, tannins, vitamin C and β-carotene contents, and further on the antioxidant activity of the heart of rattan palm (African asparagus) was studied quantitatively at this different times. Standardized methods were adopted for phytochemical, antioxidant activity of this samples.

Results: Vitamin C content, which was estimated initially at 37.04 g/100 dry matter, decreased as the cooking time in water increased. Indeed, it is noted 40, 72, and 81% of loss respectively for the cooking times of 5, 10, and 15 min in the water. Also, these different heat treatments affected the β- carotene content of African asparagus with losses ranging from 76.80 to 84%. Polyphenols were also affected by cooking. The values obtained were 5104.80 mg GAE/100g for fresh African asparagus, 5284.09 mg GAE/100g for 5 min cooking (CE5), 5233.31 mg GAE/100g for 10 min cooking (CE10), and 3536.44 mg GAE/100g for 15 min cooking (CE15). On the other hand, the tannin content of fresh African asparagus was 1954.84 mg/100g DM. However, this rate decreased continuously with heating and was estimated at 1699.93 mg/100g DM, 1429.977548 mg/100g DM, and 1035.42 mg/100g DM respectively for CE5, CE10, and CE15 samples with losses of 13.04, 26.85 and 47.03% respectively. For flavonoids, the losses were varied from 7.41 and 19.92%. In our study, the scavenging activity was found to be highest in the fresh sample, followed by CE15 and CE5.

Conclusion: Finally, boiling reduces the levels of the different parameters studied, but the antioxidant activity of African asparagus increased at the end of the 15 min heat treatment. However, a cooking time of less than or equal to 5 min in water can be advantageous for the consumer.