Date of Award

1980

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

The feasibility of producing a low cost, easy to use, and flatulence-free product from corn and cowpeas for Nigerian children was investigated. Cowpea slurry was naturally fermented for 48 hours at room temperature. The pH dropped from 6.38 to 4.20. In fermentation with the yeast, pichia guilliermondii Y-2075, for 72 hours at room temperature, the pH dropped to only 5.60. Soaking and wet milling resulted in nutrient losses. Drum drying of the product did not significantly reduce lysine levels, 90% being biologically available in most samples. Products with good biological value as measured by PER in excess of 2.0 were obtained. Results from NPR confirmed the PER trends. Protein levels increased in the corn:cowpea mixtures with increased proportion of cowpeas. Maximum complementary effect on protein quality was achieved when cowpeas contributed between 33 and 40% of the starting material. Beyond this range, protein quality was reduced even though protein content was higher. Fermentation increased protein levels in the blends. The increase was higher following yeast fermentation. Cystine content was significantly reduced in yeast fermented samples, thus lowering total sulfur amino acids. Except for tryptophan, fermentation increased the essential amino acids. Fermentation markedly affected the salt soluble protein units of the blends. SDS gel electrophoretic analysis showed that fermented samples contained only low molecular weight fractions, and the number of protein subunits were few. The degree of protein breakdown also was higher with yeast fermentation. Significant reduction in the levels of raffinose and stachyose was achieved by fermentation of cowpeas, yeast fermentation being more effective than natural fermentation in this regard. Stachyose was completely eliminated in one sample, and reduced more than 90% in others following yeast fermentation.

Pages

104

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