PHYSICOCHEMICAL CHARACTERISTICS OF FLOUR AND TECHNOLOGICAL PROPERTIES OF PROTEIN ISOLATE FROM CARIOCA BEAN

Legumes are a broad class of foods with functional physiological, nutritional and technological properties of great interest for human consumption. They are rich sources of nutrients, mainly because they have high protein levels. Within this class, it is possible to highlight the Phaseolus vulgaris L. Pinto Group, popularly known as carioca beans. The composition of carioca beans is of great interest to the industry since it can be used in different ways, for example, as a grain, whole or defatted flour, or protein isolates or concentrates. The objective of this work was to quantify the centesimal composition of carioca beans and isolate the proteins through the alkaline method, followed by acid precipitation, and evaluate the protein content, isoelectric point (pH 1, 2, 3, 3.5, 4, 4.5, 6, 7, 8 and 9), the instrumental color and emulsifying capacity in corn oil: water ratios of 75:25 and 50:50, with a protein content of 1%. In addition, the grains were subjected to milling to reduce the granulometry and increase the contact surface area. Carioca bean flour showed moisture (13.86±0.10%), proteins (22.64±0.74%; N=6.25), lipids (2.31±0.09%), ashes (6.64±0.23%) and total carbohydrates (54.55±0.79%) contents, characterizing it as a high protein raw material. The protein content of carioca bean protein isolate was 72.91±3.59% (on a dry basis), proving to be an excellent source of protein for use in the food industry. The isoelectric point of the isolated proteins was 3.7, and maximum solubilities of 57.54% at pH 1 and 86.30% at pH 9. The isoelectric point of the proteins is characterized by the pH where the lowest protein solubility occurs in the function of the equality between the charges (a sum equal to zero) of the protonated amine group (-NH3+) and the deprotonated carboxylic acid (-COO-), hydroxyls (-OH) or sulfhydryl (-SH) along the polypeptide chain and/or amino acid radicals. The instrumental color of the protein isolate (wet basis) was 79.02±0.08, 3.34±0.12 and 17.07±0.74 for parameters L*, a* and b*, respectively. In addition, it was observed that the isolated proteins presented high luminosity values and yellowish ton, located in the first quadrant of the solid color representation by the CIELab system. Generally, the yellow hue in protein isolates comes from the presence of carotenoids complexed with the proteins. The emulsification capacity was 82.50±2.50% and 75.71±1.75% for the systems containing 75:25 and 50:50 corn oil: water, respectively. The data indicate that carioca bean protein performed better in emulsions where water is the dispersed phase and oil is the continuous phase, called a water-in-oil (W/O) emulsion. The better performance of proteins isolated from carioca beans in the presence of a greater amount of oil (p<0.05) can be attributed to the more significant amount of amino acids with hydrophobic characteristics, mainly leucine, phenylalanine and valine. In this way, carioca beans have the potential for application in the food industry, whether in the whole form, ground to flour or as protein isolate.