For the toasted soybean meal, the enzymes affected the result of the extraction positively, increasing
the amount of solubilized protein, for all the times of hydrolysis, except 12 hours. The largest amount of
protein solubilized, in the three samples, was of, approximately, 2 g/100mL of suspension, for the samples
incubated with the enzymes and 1.5 g/100mL for the control, in three hours of hydrolysis. The highest
amount of solubilized protein with Flavourzyme was 2 g/100mL, in three hours of hydrolysis, and for the
control and the incubation with Alcalase, the values were of approximately, 1.8 g/100 mL and 2.2 g/100
mL, respectively, in eight hours. It should remember that, after eight hours of hydrolysis, the final pH of
the suspension begins to drop more quickly, needing a larger amount of NaOH (1 mol/L) for its final
468 Raquel Strˆher et al. / Procedia Food Science 1 (2011) 463 – 469
correction. Once the soy protein is solubilized in a basic medium, this NaOH addition can take the
responsibility for largest values.
Being considered three hours of hydrolysis as the optimum reaction time, the total amount of protein
solubilized was 2.15 g/100 mL, 2.67 g/100 mL and 2.60 g/100 mL, for the control, incubation with
Alcalase and incubation with Flavourzyme, respectively. It means that between 40 to 50% of the present
initial protein in the toasted soybean meal was solubilized in the control, and that in the incubations with
the enzymes those values were larger, staying between 50 and 65%.
These results are in agreement with what was observed in previous works [6], [4]. They concluded that
thermal treatments favor the action of enzymes, probably due to the denaturation that happens in the
material.
Marsman [3] worked with residues of soy crumbs no treated thermally, toasted and extruded, which
were previously submitted to an aqueous extraction. Their results point that there is no difference in the
solubilization of proteins by protease so much for the crumb toasted as for the not treated thermally. In
both cases, a solubilization of 40% was registered, for a temperature of 37oC, initial pH 5,0, and 24 hours
of hydrolysis.
Rosenthal [6] observed that when they used integral soy flour not toasted in hydrolysis experiments
with cellulase, hemicellulase, pectinase and protease, none of the enzymes improved the result of the
extraction in relation to the control, that in the tested conditions (50ºC, one hour in pH 5.0 more 15
minutes in pH 8.0), solubilized 80% of the protein. This fact would be attributed, according to the authors,
to the very smaller speeds of hydrolysis of the soy proteins not denatured in comparison to the denatured
substratum.
In these experiments of hydrolysis of integral soy flour toasted, with protease, the authors extracted
about of 65% of the protein initially present, which is similar to the obtained in this work. Nevertheless,
that value went smaller than to extraction obtained in the material not toasted, in the same conditions,
without using the enzyme.