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Effects of soaking in aqueous acidic and alkali solutions on removal of polyphenols and in vitro digestibility of cowpea

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Abstract

Mature dark red seeds of cowpea (Vigna unguiculata (L.) Walp.) UPL Cp 3, were subjected to several soaking treatments to remove their polyphenols. Soaking in water at room temperature for 8 and 24 h resulted in 17% and 21% loss of assayable polyphenols, respectively. Dilute solutions of alkali (Na2CO3, NaHCO3, NH4OH and KOH) and acid (CH3 COOH, HCl and H2 SO4) were more effective in removing polyphenols up to 88% than higher concentrations of alkali and acid solutions.

Vinegar (0.005–0.65 M CH3 COOH) decreased polyphenols from 55 to 62% with a 6 to 14% improvement in in vitro protein digestibility (IVPD). Commercial lime (65% CaO) removed polyphenols from seeds soaked for 8 to 24 h by 70% with 2 to 10% increase in in vitro protein digestibility. Ash removed 40 to 60% of the polyphenols after 8 and 24 h of soaking with an increase in IVPD of 7 to 13%. Total polyphenols were significantly correlated (+0.92**) with protein precipitable polyphenols (condensed tannins).

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Authors and Affiliations

  1. Institute of Plant Breeding, University of the Phillipines at Los Banos, College, 3720, Laguna, Philippines

    Antonio C. Laurena & Evelyn Mae T. Mendoza

  2. Institute of Food Science and Technology, College of Agriculture, University of the Phillipines at Los Banos, College, 3720, Laguna, Philippines

    Virgilio V. Garcia

Authors
  1. Antonio C. Laurena
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  2. Virgilio V. Garcia
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  3. Evelyn Mae T. Mendoza
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Laurena, A.C., Garcia, V.V. & Mendoza, E.M.T. Effects of soaking in aqueous acidic and alkali solutions on removal of polyphenols and in vitro digestibility of cowpea. Plant Food Hum Nutr 36, 107–118 (1986). https://doi.org/10.1007/BF01092138

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  • DOI: https://doi.org/10.1007/BF01092138

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