Use of By-Products of Selection Process of Bean (<i>Phaseolus vulgaris</i> L.): Extraction of Protein and Starch

Abstract

The industrial selection process of bean (Phaseolus vulgaris L.) produced in Northwest Argentina (NOA) region produces 7000 tons/year of by-products integrated from broken, bruised, and reduced-sized seeds. This investigation aimed to study the possibilities of using these by-products as a source of protein and starch. Samples were crushed to obtain flour (BF) with particle size of 250 µm. Starch and protein were extracted in a 6:1 and 10:1 water/flour ratio at pH 9 and 10, respectively. After centrifugation, the protein was precipitated from the supernatant at pH 4.5, and a bean protein concentrate (BPC) was obtained. The chemical composition of BF, S, and BPC was determined. Starch swelling power (SP), water solubility index (WSI), water absorption index (WAI), and syneresis in cooling (SC) and freezing (SF) conditions were determined. The proportion of molecular structure of BPC was determined using deconvolution of infrared spectrum (Amide I zone), and their solubility using Bradford reactive. The yield of obtaining processes of BPC and bean starch (BS) of high purities was 13.0 and 50.3 g/100 g of BF, respectively. The BS showed SP, WSI, and WAI values of 3.5 ± 0.5 (sediment weight g/100 g BS), 1.7 ± 1.6 (weight of the soluble BS g/100 g of BS), and 3.6 ± 0.5 (sediment weight g/weight of BS (dry solid) g), respectively. The SC was higher than SF and was double with respect to starches of other origins. The BPC solubility was 15.5 g protein/100 g BPC (pH 4.5), higher than concentrates of conventional vegetable proteins. The infrared profile showed higher proportions of deployed structures, i.e., β-sheets (22%) and random coils (18.8%), suitable for emulsifying and gelling properties. Results showed bean by-products as an alternative source of ingredients for the food industry.

Keywords

• bean
• <i>Phaseolus vulgaris</i> L.
• native starch
• protein concentrate