Protein nutritional quality of cowpea and navy bean residue fractions

Abstract

Cereal-legume protein complementation has long been recommended as a suitable strategy for augmenting the protein quality of cereal and legume based foods. However, the use of the insoluble legume residue, following protein extraction for cereal-legume protein complementation has not been widely studied. In fact, legume residue is considered a waste by-product. The protein quality of cowpea residuewheat and navy bean residue-wheat diets was determined using in-vivo and in-vitro protein digestibility assays with an AIN-93G diet as control. The diets were fed to laboratory rats over 4 weeks. The in-vitro digestibility of the diets was assessed using the pH drop and pH stat enzymatic methods. The proximate composition, limiting amino acid profile and phytohemagglutinin activity were also determined. All six diets had lower levels of the sulphur amino acid requirements for rats as expected but had higher than the FAO/WHO recommended levels for preschool children. The cowpea residue diets had higher levels of limiting amino acids than the navy bean residue diets. Phytohemagglutinin activity was only detectable in the raw cowpea and navy bean samples. All cowpea residue diets, the 30% and 70% navy bean residue diets and the control diet supported growth while the 100% navy bean residue diet resulted in weight loss. The in-vitro digestibility ranged from 77.82%-84.54% and 66.51%-79.59% for the cowpea residue and the navy bean residue diets, respectively. These ranges were lower than the control (98.1%) but correlated highly to those obtained using the in-vivo true protein digestibility method; 73.7%-87.5% and 62.6%-78.2%, respectively. These findings suggest that the cowpea residue diets had higher protein quality overall than the navy bean residue diets. In addition, it suggests that the 30:70 ratio of cowpea residue to wheat diet had the highest protein quality of all the 6 experimental diets. Legume residues after protein extraction could be recommended for human food if complemented with a cereal, particularly as it meets the amino acid pattern for preschool children. Finally, in-vitro assays can also be reliably used to assess the protein quality of foods.

Determination of the protein quality of cooked Canadian pulses

“…Alternatively, the amino acid tryptophan was limiting for navy beans, split yellow peas, chickpeas, and pinto beans. Other groups have found similar results when determining limiting amino acids in pulses (Jackson, ; Sarwar & Peace, ; Wu et al., ). The amino acid scores of the cooked pulses ranged from 0.59 (split red lentils and split green peas) to a high of 0.83 for navy beans.…”

Factors Influencing the Quality of Dietary Proteins: Implications for Pulses

“…Lentils have an average of 28.3% protein with a range of 15.9-31.4% (Grusak 2009). Tryptophan is the limiting amino acid in navy beans, black beans, and pinto beans (Sarwar and Peace 1986;Jackson 2009), whereas the quality of red kidney bean protein is typically limited by its methionine content (Wu et al 1996). The protein content of the common bean, Phaseolus vulgaris, has a narrow range, from 21.4 to 23.6% (Akibode and Maredia 2011), with the limiting amino acid depending upon the bean type.…”

“…The protein content of the common bean, Phaseolus vulgaris, has a narrow range, from 21.4 to 23.6% (Akibode and Maredia 2011), with the limiting amino acid depending upon the bean type. Tryptophan is the limiting amino acid in navy beans, black beans, and pinto beans (Sarwar and Peace 1986;Jackson 2009), whereas the quality of red kidney bean protein is typically limited by its methionine content (Wu et al 1996). The protein content of faba beans varies depending upon the cultivar but is generally high with a range of 27-34% (Duc 1997;Hacıseferoǧulları et al 2003), with the limiting amino acid differing depending upon the strain investigated, with some sources citing tryptophan (Sarwar and Peace 1986) and others suggesting methionine (Duc 1997;Hacıseferoǧulları et al 2003).…”

Evaluation of Protein Nutritional Quality of Four Soybean Varieties Grown in Western Kenya

“…The TPD value in the control and the soybean diet may be attributed to the presence of substantial quantities of essential amino acids in the diets (Khan, 2009). A previous study by Jackson (2009) reported TPD for legumes and control diet of between 62.6 to 98.1%, respectively. The TPD value observed in the present investigation shows that the soybean varieties had high protein digestibility, an indication that they can be used to improve the protein quality of diets to fulfill nutritional requirements for growth and maintenance.…”