Polyphenols, antioxidant activity, and functional properties of baobab (Adansonia digitata L) seeds soaked in monovalent ion salts

Abstract

Baobab (Adansonia digitata L.) seeds are underutilized and native to Savannah regions of Africa. The problem of the hard-to-cook (HTC) phenomenon with antinutrients exists. The application of monovalent ion salt solutions becomes important. This study analyzed the effect of soaking in deionized water, 0.5% w/v monovalent ion salts (NaCl, NaHCO3), sodium salt of a divalent ion (Na2S2O5) on the polyphenyl, antioxidant activity, and functional properties. The salts caused protein, crude fiber, vitamin C, and dry matter contents of 40.2–44.6 g/100 g, 7.78–9.46%, 3.0–3.4 mg/100 g, and 80.4–86.2%, respectively. Seed thickness, weight, and color were influenced by soaking in monovalent salt solutions. The total phenolic content (TPC), total flavonoid content (TFC), and proanthocyanidins range was 251–326 mg GAE/100 g, 236–288 mg TE/100 g, and 59–70.4 mg LE/100 g respectively. The Ferric Reducing Antioxidant Power (FRAP), DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging, and ABTS+ (2,2’-azinobis-3-ethyl benzothiazoline-6-sulfonate) ranged between 208.4–291.3 mg EA/g, 86.0–104 mg TE/g, and 98.3–110 µmol AEAC/100 g respectively. Bulk density, phytates, and oxalates were reduced significantly (p < 0.05), and gelatinization temperature increased. Monovalent salts reduce antinutrients, promote solubilization of polyphenols, modify the seed properties, and contribute to softening of the seeds.