Anais da IX Conferência Internacional de Proteínas e Coloides Alimentares

Unconventional protein sources have been widely exploited, highlighting ryegrass. It is a cereal of great cultivation versatility and agronomic characteristics, such as ease of production, high throughput and low cost, with potential for application in the food industry. Knowledge about albumin, globulin, prolamin and glutelin (Osborne solubility) fractions is essential to understand the technological performance of food proteins. Proteins have different technological properties, divided between hydrodynamic (solubility, water absorption capacity, water holding capacity, gelification, precipitation, texturing) and surface properties (emulsion and foaming capacities). This work aimed to determine the protein content of Brazilian creole ryegrass (CRG) and genetically modified (RG-LE1963) from Argentine precedence and determine protein fractions related to Osborne solubility. Ryegrass flour was defatted with hexane in 1:6 proportion (w:v) under stirring (150 rpm/2 h), filtered and dried in an oven (40 ºC/overnight) with renewal and forced air circulation (1 m/s). Protein solubilization was performed in the proportion of defatted flour: solvent (1:6 – w:v) in the following order: aqueous (albumin), 2 % saline (globulins), alkaline – 0.02 M NaOH (glutelin) and alcoholic – 70 % ethanol (prolamin). After protein extraction, the samples were centrifuged (1,700 g for 10 min), and the Kjeldahl method was used to quantify the protein content (N = 6.25). The data between the fractions were evaluated by the analysis of variance and Tukey test (P <0.05) and between the ryegrass varieties by the t-Student test (P <0.05). The protein content of the CRG (11.52 %) was lower than the RG-LE1963 (12.83 %) on a dry basis. CRG soluble protein data was 31.88 % for albumin, 14.79 % for globulins, 19.47 % for prolamins and 28.87 % for glutelins, and all fractions differ from each other (P <0.05). RG-LE1963 protein fractions showed values of 29.81 % for albumin, 13.11 % for globulins, 16.18 % for prolamins and 33.09 % for glutelins. It was observed that concerning soluble fractions, two distinct groups were quantified for RG-LE1963, with similar contents (P >0.05) between albumins and glutelins and globulins and prolamins values. In evaluating the different varieties of ryegrass, it was observed that only the glutelins fraction was higher for RG-LE1963, and the others did not show a difference between each other. Cereal proteins are characterized as reserve proteins (albumin and globulin) and structural proteins (prolamine and glutelin). The visual appearance of RG-LE1963 ryegrass, when compared to CRG, denotes larger and harder grains (probably higher hectoliter weight), likely characterized by the higher sulfur amino acid content (cysteine and methionine) of structural proteins, mainly by high molar glutelins units. The solubility method proposed by Osborne was satisfactory, and it was possible to solubilize up to 93 % of CRG proteins and 95 % for RG-LE1963. Functionalizing the proteins and their fractions can enhance their potential as a plant protein source.