Comparative effects of limited tryptic hydrolysis on physicochemical and structural features of seed 11S globulins

The effect of the limited proteolysis by trypsin on selected seed storage 11S globulins (broad bean and pea legumins, glycinin and helianthinin) was studied by high-sensitive differential scanning calorimetry, fluorescence spectroscopy and analysis of proteolysis kinetics. Different behaviour of glycinin and helianthinin, on one hand, and broad bean and pea legumins, on the other, were observed: in the first group changes in the physicochemical characteristics of the proteins due to their limited proteolysis are more pronounced in comparison with the second one, in relation with the extent of primary structure modifications. The differences observed have been evaluated in relation with the amino acid sequence features of the four 11S globulin studied and agree with the literature data concerning the protein structural changes in the course of the limited proteolysis

Avaliação da atividade dos inibidores de tripsina após digestão enzimática em grãos de soja tratados termicamente Evaluation of trypsin inhibitors activity after enzymatic digestion in heat-treated soybean

Este trabalho avalia a reativação dos inibidores de tripsina, após proteólise in vitro, de grãos de soja tratados termicamente. Para a inativação térmica dos inibidores, os grãos foram embebidos em água destilada (1:5 p/v) durante 12 horas e aquecidos em placas sob refluxo por 30 minutos. A reativação dos inibidores foi avaliada em comparação com a atividade das amostras cruas e aquecidas. A digestibilidade in vitro das proteínas variou de 47% ('OC-13') a 59% (Paraná), apresentando uma melhora, em média, de 32,6% com o aquecimento. A atividade dos inibidores de tripsina para os grãos crus variou de 122 a 206 UTI/mg de amostra, e os valores correlacionaram-se negativamente com a porcentagem de digestibilidade (r = -0,9177). Os inibidores tiveram suas atividades totalmente inativadas com o aquecimento dos grãos, os quais apresentaram porcentagem de recuperação, em média, de 40%. Com o aquecimento, a inativação dos inibidores provavelmente ocorre por complexação com os componentes do grão, o que leva à recuperação da atividade com o processo de digestão enzimática.<br>This work evaluates the trypsin inhibitors reactivation, after in vitro proteolysis, of heat-treated soybean. For the inhibitors thermal inactivation, soybeans were soaked in distilled water (1:5 p/v) during 12 hours and heated on reflux plates for 30 minutes. The inhibitors reactivation was evaluated in comparison with the activity of raw and heated samples. The in vitro digestibility of proteins ranged from 47% ( 'OC-13') to 59% ('Parana'), showing an average progress of 32.6% with the heating. The trypsin inhibitors activity ranged from 122 to 206 UTI/mg for the raw sample, and the values correlated negatively with the digestibility percentage (r = - 0.9177). The inhibitors had the activities totally inactivated with the heating of soybeans, which showed an average recovering percentage of 40%. With the heating, the inactivation of inhibitors probably takes place by complexing with the soybean components, which leads to the recovering of activity with the enzymatic digestion process

Functional properties of protein isolate obtained from physic nut (Jatropha curcas L.) seed cake

Physic nut (Jatropha curcas L.) protein isolate was successfully achieved from physic nut seed cake by an alkaline extraction and followed by an isoelectric precipitation. The protein isolate had small amounts of phorbol esters, phytic acid, and saponin without any lectin. Its minimum and maximum solubility were at pH 4.0 and 12.0, respectively. Its water and oil binding capacities were 3.22 g water/g protein and 1.86mL oil/g protein, respectively. Its foaming capacity and emulsion activity showed high values in a range of basic pHs. Its foaming and emulsion stability values decreased with increasing time and exhibited high levels under basic pH conditions. Physic nut protein isolate had unique functional properties in water binding capacity, emulsion activity, and emulsion stability indicating an important role in food systems. It may be applied to salad dressing, mayonnaise, sausage, and meat products. Therefore, physic nut seed cake has a potential to be exploited as a novel source of functional protein for food or feed applications. © KoSFoST and Springer 2011