Evaluation of iron solubility in the presence of whey protein hydrolyzed by different
enzymatic systems
Maria Elisa Caetano Silva¹; Maria Teresa Bertoldo Pacheco²; Flavia Maria Netto¹
¹Department of Food and Nutrition, Faculty of Food Engineering, University of Campinas,
(UNICAMP), Rua Monteiro Lobato 80, 13083-862 Campinas, São Paulo, Brazil
²Center of Food Science and Quality; Institute of Food Technology (ITAL), Av Brasil 2880,
13070-178 Campinas, São Paulo, Brazil
Food supplementation with iron salts, like FeSO4, is a strategy for treatment of iron
deficiency anemia. However, in salt form this mineral has low bioavailability. An alternative to
increase it is by binding with peptides. This study aimed to evaluate the interaction between iron
and whey peptides, obtained by WPI hydrolysis with different enzymes. Whey protein
hydrolysates obtained with Alcalase (HA), pancreatin (HP) or Flavourzyme (HF) were
fractionated by ultrafiltration (cut-off 5kDa) and lyophilized. The fractions <5kDa were evaluated
for their iron-binding ability. Solutions of 4% protein (w/v) in de-ionized water were added of
FeCl3 (0.1% Fe w/v) and the pH was adjusted to 7.0. After 60 min under stirring (25±2 °C),
+3
solutions were centrifuged and supernatants were analyzed. The Fe
content in the
supernatants was 45.3, 47.6 and 25.4% in relation to the initially added, for the HP, HF and HA,
respectively. As FeCl3 is insoluble in pH 7.0, these results suggest that the iron solubility is due
to interaction Fe+3-peptides. Zeta potential analysis showed that HP presents higher negative
charge (-22.3mV), indicating the presence of more deprotonated carboxylic groups, while HA
and HF present lower charge, -15.6 and -15.1mV, respectively (p<0.05). The hydrolysis process
results in exposure of these groups, including side chains of Asp and Glu residues, which are
among the principles iron-binding sites. Although HF and HA showed similar negative charge,
the higher ability of HF to maintain iron in solution suggests that this enzyme action provided the
exposure of other groups with high iron-binding affinity.