CHARACTERISTICS OF LIMA BEAN (Phaseolus lunatus L.) AS A SOURCE OF VEGETABLE PROTEIN AND POTENTIAL EMULSIFYING CAPABILITY FOR USE IN FOODS

Lima bean (LB) is a legume native from the Andes and Mesoamerica. It has great economic importance for Brazil due to its adaptability to semi-arid, arid and temperate climates. Understanding the chemical composition and some characteristics of these components is important to identify the technological potential of the grain, especially the proteins. This work aimed to determine the centesimal composition of the LB protein isolate and determine the protein content, the isoelectric point (pH from 1 to 9) and the instrumental color of the lima bean protein isolate (LBPI), as well as to evaluate the emulsifying capacity (EC) of the proteins. The LB grain was ground to flour, defatted with hexane in a 1:3 ratio (flour:solvent) under stirring for 2h, filtered and dried in an oven (40°C/overnight). The alkaline extraction method with subsequent precipitation with 10% C6H8O7 was used to obtain LBPI. The emulsions were performed with a combination of 50:50 and 75:25 of corn oil: water, with the protein concentration set at 1% and the data evaluated by the t-Student test (P<0.05). LB flour showed 12.78±0.24% moisture, 1.37±0.05% lipids, 4.80±0.13% ashes, 24.57±0.65% proteins and 56.48±0.71% of total carbohydrates. These data demonstrate that LB is rich in proteins, with considerable levels of minerals and low in lipids. LBPI had a protein content of 77.19±7.54% (on a dry basis) and the isoelectric point curve showed solubility in an acid medium (pH 1) of 64.06% and an alkaline medium of 95.96%, with the lowest solubility evidenced at pH 4.25, thus determining the isoelectric point of this protein. The isoelectric point is the pH at which the protein has the lowest solubility due to the greater attraction between the positive and negative charges. The use of protein isolates in food is a common tool, and the color of proteins can often change the visual perception of the consumer in the food to which it is applied. However, it was observed that the LBPI had a light color (L*=82.41±0.22), with a* axis coordinates close to neutrality (-1.74±0.07) and a yellowish hue (b* =15.66±0.28), characterized by the presence of carotenoids complexed to proteins (in wet basis). The BL protein is mainly composed of hydrophobic amino acids (alanine, isoleucine, leucine, phenylalanine, proline and valine), followed by neutral polar amino acids (threonine, serine, asparagine and glutamine) and polar amino acids (basic- lysine, arginine and histidine; and acids – aspartic and glutamic). A protein's profile of amino acids allows it to present a potential emulsifying property. In this sense, it was observed that the EC in the 50:50 system (oil: water) was 63.75±4.15% and lower (P=0.001) for the 75:25 system (oil: water), which presented an EC of 81.25±2.17%, indicating that the LBPI presented a better performance in water-in-oil (W/O) emulsions. Therefore, it was demonstrated that LB could be an alternative as a plant source of protein applied in emulsified food formulations, such as meat products and sauces. From a nutritional point of view, incorporating this isolate into food will also be positive due to its high protein value.