Effects of Condensed Tannins on the in Vitro Protein Digestibility of Cowpea [Vigna unguiculata (L.) Walp.]

Abstract

Condensed tannins of eight cowpea [Vigna unguiculata (L.) Walp.] cultivara determined by the protein precipitation method were localized in the seed coat and concentrated in the cooking broth. They were positively correlated with seed coat color (r = +0.64⋆⋆), which varied from white to light brown, dark red, and black. Cooking increased in vitro digestibility by 6-8% significantly. The digestibility of the cooked seeds with cooking broth was significantly different from that without the cooking broth. Replacing the cooking broth of the cooked white seeds with the broth of the cooked light brown and black seeds resulted in a decrease of 1.4% in digestibility. Replacing the cooking broth of the cooked light brown and black seeds with that of the white resulted in an increase in digestibility of 3 and 4%, respectively. The change in the relative nutritive value determined by Tetrahymena pyriformis W upon interchange of broth was greater (5-31%). Significant negative correlations were observed between condensed tannins and protein digestibility (r = −0.87⋆⋆) and relative nutritive value (r = −0.96⋆⋆). Polyvinylpolypyrrolidone when added to homogenized cooked seeds at 4 and 6 mg/mL increased protein digestibility by 3.7%. Isolated cowpea condensed tannins and commercial tannic acid decreased the digestibility of raw white cowpea and casein by 3.6 and 5.1% and 2.6 and 4.2%, respectively. © 1984, American Chemical Society. All rights reserved.

Source or Periodical Title

Journal of Agricultural and Food Chemistry

ISSN

218561

Page

1045-1048

Document Type

Article

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