3. Results and Discussion
The functional properties increase the importance of the alimentary proteins, complementing its wellknown
nutritional value. They are defined as the properties physical-chemistries that govern its
performance and behaviour in food systems, during its preparation, storage and consumption. They are
influenced by the nature and extension of the interactions of the proteins with themselves, with other
components and with the water.
The solubility is a functional property sometimes difficult to obtain, but perhaps it is the one that more
improves the functionality of a protein. The soy contains great amount of proteins, however, about of 90%
of the soy proteins are globulins, with minimum solubility around the pH 4.5. It makes necessary,
therefore, to accompany the pH of the suspensions, in the different times of hydrolysis, to certify that the
soy protein is in its soluble form, that is to say, that the pH is greater than 5.0.
The pH values, measured before and at the end of the hydrolysis of suspensions at 10% of toasted and
not toasted soybean meal, in the several times, are presented in the Figures 1 to 3. The rehearsals were
carried out in agreement with the methodology previously presented.
It was observed for the not toasted soybean meal that, in the cases of the left side of Figures 1, 2 and 3,
the pH of the suspension stayed in values between 7.0 and 6.5 up to six hours of hydrolysis. At seven
hours it dropped for values below 6.0, and for larger times, it decreased to values about of 4.5, that
correspond to the isoeletric point of the soy protein. In the toasted soybean meal, right side of Figures 1, 2
and 3, it was observed that the pH of the suspension stays constant about of 6.0, up to seven hours of
hydrolysis, dropping slightly in eight hours and, for longer times, it decreased more, being reached values
about of 5.0. That means that for hydrolysis times higher than 8 hours, in the case of the not toasted
soybean meal, and 9 hours for the toasted soybean meal, most of the protein is in the precipitate and not in
its soluble form.