Use of response surface methodology to describe the effect of time and temperature on the production of decoloured, antioxidant and functional peptides from porcine haemoglobin by sub-critical water hydrolysis

• Peptides from porcine haemoglobin were produced using subcritical water hydrolysis.
• Surface response methodology predicted the peptide composition of the hydrolysate.
• Peptides showed improved antioxidant and functional properties.
• At 180 °C after 240 min the 83% of haemoglobin was converted into yellowish peptides.

Sub-critical water hydrolysis coupled to oxygen injection was used to hydrolyse porcine haemoglobin. The effect through process time of three different temperatures were tested (120–180 °C), under medium pressures (40 atm.). Peptides obtained at 180 °C showed good antioxidant and functional properties, and the best yield (83%). Moreover, the final product presents almost complete discolouration, thus increasing the range of haemoglobin hydrolysates uses in food industry. Regression modelling was used to investigate the main effects of hydrolysis time and temperature. Both were found to be significant. Predicted models were found to be significant (p < 0.05) with high coefficients of determination (R2). This study found that the average peptide size can be predicted from the temperature and process time; besides, evidence seems to show that preferential targets exist to break down the haemoglobin. This method can transform large amounts of proteins into appreciable low-molecular-weight peptides in a simple and fast way.