Date of Award:

1981

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Sciences

Advisor/Chair:

Dr. D. K. Salunkhe

Abstract

Protein content of the Great Northern beans was 26.10 percent on a dry weight basis. The apparent isoelectric pH of the NaCl extractable proteins was about 4.4. Among the several solubilizing agents, Na2CO3, K2S04, sodium dodecyl sulfate (SDS), and NaOH at the respective concentrations of 0.5, 5.0, 5.0 (all w/v), and 0.02 N were the best protein solubilizing agents, solubilizing 93.6 grams Lowry protein per 100 grams Kjeldahl protein. AIbumins and globulins accounted for 21.18 and 73.40 percent, respectively, of the total bean proteins. The bean proteins were fractionated and protein concentrates and protein isolates were prepared. The bean flour proteins, albumins, globulins, protein concentrates, and protein isolates (heretofore referred to as fractions) were studied electrophoretically.

Several functional properties of the fractions were investigated. Protein concentrates had the highest water and oil absorption capacity (5.93 and 4.12 g/g, respectively) and emulsion capacity (72.6 g oil emulsified/g). Albumins registered the highest emulsion stability (780 hours at 21 °C). Foaming performance of the Great Northern bean proteins was fair and concentration dependent. Sorption isotherms studies indicated that the bean flour had higher equilibrium moisture content at corresponding temperature and equilibrium relative humidity than other fractions. Buffer capacity of the bean proteins over a pH range of 4-8 was modest. Modification (succinylation and oxidation) improved the water and oil absorption capacity of the bean proteins. Globulins registered the highest stickiness (92 N) among all the fractions.

Alkali solubilization of the bean proteins resulted in significant reduction in trypsin and chymotrypsin inhibitory activities and elimination of hemagglutinating activity. Protein concentrates were essentially void of flatulence activity.

Amino acid profiles indicated that the bean flour proteins, albumins, and protein isolates contained high acidic amino acids, while globulins and protein concentrates were characterized by high proportions of hydrophobic amino acids. Sulfur containing amino acids and leucine were the first and second limiting amino acids in the Great Northern bean proteins. Heat treatment of the fractions improved the in vitro protein digestibility.

Baking studies indicated that replacement of wheat flour by the bean flour and the protein concentrates for improved nutritionality of cookies and bread was possible without adversely affecting the sensory quality attributes. In cookie preparation, bean flour and protein concentrates could replace wheat flour up to 30 percent and 20 percent (by weight), respectively; the corresponding figures for the wheat flour replacement in breadmaking were 10 percent and 10 percent (by weight). Fermentation of the Great Northern beanrice blends suggested the potential for these beans in developing fermented foods.

The beans contained 59.20 percent (on a dry weight basis) of starch. Starch granule size ranged from 12 X 12 μm to 58 X 40 μm (length X width) and the granule shape was round to oval to elliptical, and in certain cases, concave as well. Lamellae were present on all the starch granules observed. Amylose content of the starch was 10.20 percent (on starch basis). Stable gel formation by the bean starch was observed at concentrations of 7 percent and above (w /v). The viscoamylographic studies of the isolated starch indicated the restricted swelling character of the bean starch. Solubility and swelling of the bean starch was both pH and temperature dependent. The addition of free fatty acids to the isolated starch reduced the viscosity and raised the gelatinization temperature of the bean starch. Modifications (acetylation and oxidation) of the isolated starch resulted in altered solubility and swelling characteristics. Replacement of wheat flour by the bean starch caused an increase in alkaline water retention capacity.

The bean contained an arabinogalactan type mucilage principle (arabinose:galactose ratio of 2.0: l.7), the viscosity of which was dependent on concentration, pH, and temperature.

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