Enzymatic hydrolysates of casein and soybean were treated with alginate immobilized chicken intestinal mucosa, as an aminopeptidase source, to bring about debittering. The mucosa was hygienised by irradiation (20 kGy) which brought about a complete decontamination of the tissue accompanied by a 20% loss in aminopepidase activity. The effectiveness of the process was demonstrable by a higher acceptability and a marked reduction in bitterness scores for casein (from 4.4 to 2.5) and soybean (from 3.8 to 2.2) in organoleptic analysis. The action of aminopeptidases to bring about this change was corroborated by a concomitant increase in free amino acids and a decrease in average peptide length of the samples after treatment. The RP HPLC profiles of casein and soybean protein hydrolysates before and after treatment showed a higher content of peaks in the hydrophilic region suggesting a decrease in hydrophobic peptides, responsible for bitter taste, in both the samples. Immobilization of the mucosal tissue in alginate afforded an increased pH and temperature tolerance to the enzymes. The possibility of the system for continuous operation over extended time periods is also discussed. (C) 2010 Elsevier Ltd. All rights reserved.