BEAN BREAD TO IMPROVE PUBLIC HEALTH: IMPACTS ON BREAD QUALITY, CONSUMER PERCEPTION, AND LIFE CYCLE ANALYSIS

Abstract

Since the Green Revolution, the intake ratio of cereal grains to pulses has increased considerably, coinciding with marked declines in dietary quality, specifically protein and fiber consumption. This shift has contributed to reduced dietary protein quality and increased risk of essential amino acid deficiencies, particularly lysine, in many populations. In chapter one, we further looked at the environmental cost of imposing agricultural practices. Previous studies have shown that pulse flours, such as cowpea and common bean, incorporated into staple foods like wheat bread could offer a promising strategy to improve protein quality and micronutrient intake. This could also help to enhance sustainability through resource use and nitrogen fixation, and support resilient food systems. In the second chapter, we examined the development of a stealth health approach to enhancing lysine consumption in Nigeria, with a focus on urban populations. We also examined the impact of Nigerian cowpea, U.S. cowpea, U.S. roasted cowpea, and common bean flours on protein and amino acid levels, as well as measures of bread quality. Using a dose-response approach to substitution, the impacts of improving the nutritional quality of bread are juxtaposed with effects on traditional metrics of bread quality. Substitutions of wheat flour with 1- 50% with cowpea or common bean flour were assessed, and impacts on the anti-nutrient lectin were also evaluated. Up to 5% substitution with either pulse flour type did not diminish bread quality. We observed that cowpea flours had higher protein concentrations (21-23%) than common bean flours ( 19%), and cowpea flour from Nigeria had 10% higher protein content, resulting in 12% larger loaves than cowpea sourced from the USA. Comparison of common bean varieties (Rattler and Diamondback) showed only small differences in water absorption; otherwise, bread quality wasnot affected by variety. Roasting of the U.S. cowpea prior to milling had no effect on loaf volume or water absorption. At higher pulse flour percentages (10 and 20%), adding ascorbic acid (AA) and vital wheat gluten (VWG) improved the loaf volume by 14-26% and increased dough water absorption by 3-7%. By increasing pulse flours, we demonstrate a marked improvement in the nutritional quality of bread. It is imperative to identify lectin null cultivars since baking bread is insufficient to completely eliminate active lectins for uncooked pulse flours. More so, in chapter three, we examined the impact of cowpea-based carbohydrate substitutions on sensory attributes and consumer perceptions of wheat bread formulations. Since cowpea (Vigna unguiculata) flour could offers a plausible way to increase protein and fiber in a familiar staple, although consumer acceptance may depend on substitution level, flour source, pretreatment, and formulation strategy. This study evaluated sensory responses and stated willingness to pay (WTP) for wheat breads containing cowpea flour across five experiments involving 88 to 142 participants per experiment. The experiments compared: (i) wheat bread with breads containing 5% or 10% US raw cowpea flour; (ii) untreated 10% breads made with Nigerian raw, US raw, or US roasted cowpea flour; (iii) additive effects of ascorbic acid (AA), vital wheat gluten (VWG), or AA+VWG in a 10% US raw formulation; (iv) the same 10% flour comparison after addition of AA+VWG; and (v) a high substitution bread made with 33% cooked Nigerian cowpea flour with or without sucrose. Cowpea inclusion increased protein and dietary fiber across formulations. At 5% and 10% substitution, overall acceptability and WTP remained statistically similar to the wheat control, although appear ance declined modestly. In the untreated 10% comparison, bread made with Nigerian cowpea flour received higher sensory scores and higher WTP than breads made with US raw or US roasted flour. When AA+VWG were added, those differences were no longer statistically significant. VWG alone lowered sensory scores in the 10% US raw formulation. By contrast, 33% cooked cowpea flour reduced sensory ratings and WTP, and adding sucrose did not restore equivalence to wheat bread. Across experiments, taste and texture were the strongest drivers of overall acceptability. These data suggest that modest cowpea substitution can improve bread nutrient density without an obvious market penalty, whereas high substitution remains difficult to mask sensorially. Because the flour source, origin, and processing history were not fully cross-checked, the study should be interpreted as a formulation screening rather than a definitive cultivar trial. In chapter four, we looked at the impact of bean bread on climate change, freshwater ecotoxicity, marine ecotoxicity, terrestrial ecotoxicity, fossil resource scarcity, freshwater eutrophication, marine eutrophication, land use, ozone depletion, and water use. The environmental impact of bean bread made with 10% flour from common beans (Phaseolus vulgaris) and cowpea (Vigna unguiculata), using 1 kg of bread as the functional unit was evaluated and compared with bread made from 100% wheat flour. The system boundary was cradle to baking gate, and the ReCiPe midpoint (H) method was used to assess impact categories. Fertilizer use, field emissions, and field operations are the main factors affecting the environmental impacts of the crops produced to make the flours. For climate change, Irrigated cowpea and Pinto beans had the highest impacts mainly due to field emissions. Freshwater ecotoxicity was high in Pinto beans, Wheat, and Irrigated cowpea. Nigerian cowpea was high in marine and terrestrial ecotoxicity. Fossil resource scarcity was high in Irrigated cowpea. Non-irrigated cowpea was high in freshwater eutrophication and land use impacts. Wheat was high in marine eutrophication and water use. Proofing and baking contributed most to climate change, ecotoxicity, and freshwater eutrophication while ingredients contributed most to marine eutrophication, land use, and ozone depletion. For water use, proofing, and ingredients contribute the most to the total impact. Environmental impacts were also evaluated at the ingredient level for the production of 1 kg of bread and uncertainty analysis was applied to all impact categories using Monte Carlo simulation at 1000 iteration. We also used a base uncertainty value of 20%, and a pedigree matrix to evaluate uncertainties for all breads to assess the variabilities. We reported uncertainty results using 95% confidence intervals. The result revealed that wheat flour accounted for about 70-80%, and pulse flour accounted for about 11-36% and were the major contributors across all bread categories. Additives to bread reduced environmental impacts per kg of bread. Reducing the electricity used for baking and proofing by 20% cut the effects of climate change and freshwater eutrophication by 18% and this suggests that using bean flours in bread may be more environmentally friendly especially using additives such as ascorbic acid (AA) and vital wheat gluten (VWG).