Proteínas hidrolisadas de soro de leite com propriedades bioativas associadas à redução de fatores de risco de doenças na infância

Abstract

Among the chronic diseases, the obesity has reached global epidemic proportions affecting all age groups and has been associated with hypertension and oxidative stress. The treatment of obesity involves changes in lifestyle and healthy eating habits and providing an attractive and healthful food to infant diet remains a challenge. In this study, a pancreatin and the proteases from Bacillus licheniformis, Aspergillus oryzae and Aspergillus sojae were employed to obtain hydrolyzed whey proteins with high oligopeptide content as well as with antihypertensive and antioxidant activities, which could be used in the development of infant formulas for the obesity treatment. The protein hydrolysates were characterized in relation to the degree of hydrolysis (DH) by different methods (soluble protein content; formol titration; orthophtalaldehyde and osmometry), and their peptide profile was analyzed by using the high performance size-exclusion liquid chromatography for the fractionation step followed by the Rapid Correct Fraction Area method for quantifying the peptides and free amino acids. The correlation between these parameters (degree of hydrolysis and peptide profile) was established. Also, the inhibitory activity against the angiotensin-converting enzyme (ACE-IA) and the antioxidant activity of the hydrolysates were in vitro evaluated. The use of the Bacillus licheniformis protease (E:S 8:100) and pancreatin (E:S 2:100, 3:100, 4:100 and 8:100) yielded hydrolysates with the highest sums of di- and tripeptide and free amino acid contents (9.99 and 11.28%, respectively) as well as the lowest amount of large peptides (44.61 and 44.13%, respectively). Regarding the DH, the highest results were produced by the soluble protein content method for the pancretin (36.41%), the Bacillus licheniformis (44.70%) and Aspergillus oryzae proteases (32.79%), whereas for the Aspergillus sojae protease this result was obtained with the orthophtalaldehyde method (20.17%). In several cases, a positive and significant correlation (p < 0.05) of strong intensity (r > 0.7) was observed among the DH determining methods and the intensity changed in function of either the determining method or the enzyme type. Additionally, in many cases the DH results were significant and positively correlated with di- and tripeptide contents and negatively correlated with the large peptide content. In this study, twenty four WPC hydrolysates were prepared and their ACE-IA was in vitro evaluated giving rise to results ranging from 2.02 to 96.66%, with eleven samples exhibiting very high ACE-IA (> 80%). The hydrolysates obtained with the Bacillus licheniformis protease exhibited the greatest ACE-IA results (average of 85.96%) when compared to the other enzymes at all E:S ratios. The enzymatic hydrolysis of whey proteins also led to a great variability of the results obtained for the antioxidant activity (3.79% to 90.76%). The action of the Aspergillus sojae protease produced hydrolysates with the highest values of antioxidant activity by the DPPH (59.70%) and deoxyribose (58.77%) methods at most of E:S ratios. For the pyrogallol method, the highest results (48.70 to 90.76%) were found when the hydrolysis was conducted by the action of the Bacillus licheniformis protease at all E:S ratios. It can be inferred that it was possible to optimize the hydrolytic conditions to obtain whey protein concentrate hydrolysates with high nutritional value and antihypertensive and antioxidants properties.