Effects of Cooking Time on Some Antinutrients Contents and in vitro Digestibility of Leaves Proteins of Gnetum spp

摘要

Gnetum spp are creepy lianas well known by people around Guinea Gulf most notably for their edible leaves. With the aim at contributing to nutritional valorization of these leafy vegetables, we studied the effects of cooking time on some antinutrients contents and on proteins digestibility. Phytates, phenolic compounds, tannins, oxalates and proteins were extracted and evaluated by conventional methods. In vitro digestibility of proteins was estimated using pepsin and pancreatin. Results showed that Phytates contents in G. africanum leaves were 240.23±14.25 against 90,68±3,09 mg/100g (DM) for G. buchholzianum. After two hours of cooking, values decreased significantly (P< 0.05) to 208.84±1,57 and 82.146±5.134 mg/100g (DM) respectively. In the same time, contents of phenolic compounds decreased from 507.20±21.53 to 245.56±3.04 and from 460.37±3.09 to 230.83±13.87mg/100g (DM) for the two species. Tannins contents were 298.09±13.70 and 222.73±13.90 mg/100g DM for G. africanum and G. Buchholzianum. Retention rates after 2 hours of cooking were 34.55% and 46.28% respectively. Oxalates contents varied between 5.10±0.07 and 6.76±0.14 mg/100 DM with retention rates ranging from 22.85% to 26.50% during the same cooking time. Proteins contents (16.04±0.05 and 18.14±0.16% g DM) decreased significantly (P< 0.05) by half while in vitro digestibility of proteins doubled after 2 hours of cooking. This study shows that Gnetum spp vegetables have high contents of some antinutrients which important amounts are easily remove with long cooking time. This treatment improves digestibility of theirs proteins.