Non-bitter Protein Hydrolysates

Abstract

Deboned, defatted chicken meat (78% protein, d.b.) was reacted with pancreatin to produce a bitter hydrolysate as judged by a trained sensory panel. The hydrolysis was carried out at 60°C, an enzyme concentration of 4.3%, pH of 8.55 (carbonate buffer) and a salt concentration of 0.6 M (KC1). These conditions resulted in >95% substrate solubility after 120min. Enzyme activity was monitored by formol titration. Samples for sensory analysis and α amino nitrogen were taken after 0, 30, 60,90 and 120min and it was found that when chicken alone was reacted with enzyme a steady increase in bitterness was perceived by the panel up to 90min, reaching a level equivalent in quinine concentration to over .003%. The α amino nitrogen curve was similar in shape to that for bitterness, increasing from about 6 to 23mg/ g total protein. When gelatin was added (1:1 protein basis, enzyme level constant) the α amino nitrogen curve was not substantially altered but no significant increase in bitterness was perceived. When glycine, which is a sweet amino acid found in large quantities in gelatin, was added to the chicken hydrolysate at the same level that would have been in a chicken: gelatin preparation, it significantly reduced bitterness while proline and hydroxyproline alone did not. It was concluded that the mechanism by which gelatin affects protein hydrolysate may be the ability of the endogenous amino acid glycine to mask bitterness.