Physical and functional characteristics of selected dry bean (Phaseolus vulgaris L.) flours

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Abstract

Many varieties of dry beans (Phaseolus vulgaris L.) are available with entirely different physico-chemical and sensory characteristics. Selected dry bean varieties (red kidney, small red kidney, cranberry and black) were processed into flour and analyzed for the physico-chemical and functional characteristics. The bulk density of the beans flours varied significantly (p < 0.05) from 0.515 g/ml for black bean flour to 0.556 g/ml for red kidney bean flour. The small red kidney bean flour had the highest water absorption capacity (2.65 g/g flour) while black bean flour showed the lowest at 2.23 g/g flour. Significant differences were observed for oil absorption capacities of bean flours, which ranged from 1.23 g/g for small red kidney bean flour to 1.52 g/g for red kidney bean flour. The bean flours emulsion capacity and stability and foaming capacity and stability also varied significantly and was variety-dependent. The highest apparent viscosity, 0.462 Pa.s, was recorded for small red kidney bean flour whereas black bean flour exhibited the lowest value of 0.073 Pa.s at 30 g/100 ml water content in the flour dispersions. The force-deformation curves for doughs from different bean flours showed that black bean flour had the highest peak force or hardness value of 90.7 N followed by doughs from cranberry, small red kidney and red kidney bean flours. The results of this study offer useful data on bean flours' potential uses in different food products.

Introduction

Legumes occupy an important place in human nutrition, especially among the low-income groups of populace in the developing countries. They provide a good source of protein, which is 2–3 times that of cereal grains, and are a rich source of dietary fiber, starch (Osorio-Diaz et al., 2003) minerals and vitamins (Kutos, Golob, Kac, & Plestenjak, 2002). The various types of beans are a staple food and a low-cost source of protein in many countries where protein energy malnutrition is prevalent widely (Van Heerden & Schonfeldt, 2004). Dry beans are rich in non-nutrient components, too; Wu et al. (2004) investigated the oxygen radical absorbance capacity (ORAC) of common foods consumed in the U.S. Their data showed that red kidney beans had the highest total antioxidant capacity per serving size as compared to all other foods, including many fruits commonly believed to be rich in antioxidants.

The inclusion of legumes in the daily diet has many beneficial physiological effects in controlling and preventing various metabolic diseases such as diabetes mellitus, coronary heart disease and colon cancer (Tharanathan & Mahadevamma, 2003). It has been reported that the protective effects of dry beans in disease prevention, such as against cancer, may not be entirely associated to dietary fiber, but to phenolics and other non-nutritive compounds (Oomah, Tiger, Olson, & Balasubramanian, 2006), as polyphenols from dry beans may possibly act as antioxidants, hindering the formation of free radicals (Boateng, Verghese, Walker, & Ogutu, 2008). In addition, legumes belong to the food group that elicits the lowest blood glucose response. The general consensus on healthy eating habits favors an increase in the proportion of legume-based polymeric plant carbohydrates including starch in the diet. The role of legumes as a therapeutic agent in the diets of persons suffering from metabolic disorders has been reported previously (Shehata et al., 1988, Simpson et al., 1981).

Dry bean flours can be used as functional ingredients to improve the nutritional quality of a variety of processed food products (Horax, Hettiarachchy, Chen, & Jalauddin, 2004). One recent study reported on the use of pinto bean flour in tortillas (Anton, Lukow, Fulcher, & Arntfield, 2009). The application of various technological processes to legumes can increase their use as an ingredient in manufactured food products. Processing improves the nutritional quality of dry beans by reducing the content of anti-nutritional factors and, at the same time, diversifies their use as ingredients by altering their functional properties.

The fact that dry beans, apart from being nutrient-rich, are gluten-free offers significant opportunities for exploiting bean flour use in different food systems. The number of new gluten-free products introduced in the United States increased by five-fold, from 135 in 2003 to 832 in 2008 (Clemens & Dubost, 2008). They further reported that the sales of gluten-free products are projected to grow at an annual rate of 25% for the next several years. However, there is limited information published on bean flour's physico-chemical characteristics and functional properties, which eventually influence the product characteristics and, in turn, sensory quality and consumer acceptability. The present study was undertaken with an objective to produce flours from selected dry beans and to characterize selected functional properties of these flours.

Section snippets

Materials and methods

The red kidney, small red kidney, cranberry and black beans (Phaseolus vulgaris L.) were procured from Bayside Best Beans, LLC (Sebewiang, Michigan, U.S.A.) and stored at 4 °C until processed. The dry beans were analyzed for their proximate composition (Table 1), using two replicates; all the other analyses were done on three replicates.

Hunter color, hue, and chroma

The Hunter color parameters recorded for whole beans and bean flours are shown in Table 2. Seed coat Hunter color “L” values differed significantly (p < 0.05) across bean types, with black beans having the lowest (11.49) and the cranberry beans the highest (32.20) “L” values, indicating a higher and lower degree of lightness, respectively. Red kidney beans with 9.40 had the highest Hunter color “a” values, which different significantly to all other beans. The cranberry beans had the highest “b”

Conclusion

The present study showed a varying degree of differences in the physical and functional properties of flours from commonly used bean types. The protein, fat, or ash content of bean flour was shown to have minimal or no effect on the most of the flour properties studied. Based on the previously reported results, most of the functional properties of bean flours were different to that of wheat flour. The information on these properties is important for developing new products using bean flours.

Acknowledgement

This research was funded by the Department of Biotechnology, New Delhi. India under the Overseas Research Associate program, which author Dr. Ramasamy Ravi completed at the Department of Food Science and Human Nutrition, Michigan State University, East Lansing. Michigan, U.S.A.

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