Cold-set gelation of soy and amaranth protein isolates blends in the presence of calcium. Study of appropriate balance of interactions for gelation

MARINACCI ANABELLA ; SPERONI FRANCISCO; PIERMARIA JUDITH

Rio

Congreso; International Conference on Food Proteins and Colloids (CIPCA); 2023

The consumption of plant-based foods was increased in recent times for several reasons, including the replacement of animal proteins due to the choice of vegan diets and the need to reduce carbon and water footprints. In this sense, soy proteins have been applied in the development of new products due to their interesting functional and nutritional characteristics. On the other hand, amaranth proteins, scarcely applied industrially, include beneficial bioactive peptides for health. Soy proteins can form cold gels in the presence of calcium, for this reason, it was decided to evaluate the possibility of obtaining cold mixed gels from a lyophilized mixture of proteins previously denatured by temperature in the presence of calcium. Protein dispersions (2 or 4% w/w) were prepared from soy protein isolate and amaranth protein isolate in a 80:20 ratio, calcium was added (0.075 – 0.25 mmol Ca/g protein) and denatured at 95°C for 25 min and then lyophilized. The preparation of the gels was carried out by rehydrating the protein powders to a content of 10 or 13% w/w. The gels obtained after the three steps (denaturation, lyophilization, cold re-dispersion) were characterized by evaluation of z potential, water holding capacity, solubility in different media, color and texture. Gelation was favored when using high protein contents during denaturation (4%) and rehydration (13%). Regarding the Ca:protein ratio, 0.100 mmol Ca/g protein was the most suitable for establishing a balance between attractive and repulsive forces in the matrix that presented a high water holding capacity (99.1%). A lower Ca:protein ratio did not allow the formation of structured gels, probably because there was not enough calcium to shield the negative charge of the proteins and allow the establishment of attractive interactions; while a higher Ca:protein ratio generated aggregates and precipitates probably due to the formation of calcium bridges and excess of other attractive interactions between proteins. The gels presented a high solubility in water, which would indicate a weak association between the proteins and that the effect of calcium was mainly to attenuate the electrostatic repulsion of the proteins and allow the approach and establishment of attractive interactions such as hydrogen bonds and hydrophobic interactions. The presence of amaranth proteins in the gels provided a brownish color and greater adhesiveness than those corresponding to gels formed solely with soy protein. The results indicate that it is possible to generate gels from cold rehydration of proteins previously denatured in the presence of calcium, which would be the basis for producing easy-to-prepare foods. The possibility of forming these gels depended greatly on the balance between electrostatic attractions and repulsions. This balance was a function of the z potential and the ionic strength, which in turn were a function of the Ca:protein ratio and the calcium concentration, respectively.