Carboxypeptidase, bitterness elimination

Enzymatic hydrolysates of various proteins have a bitter taste, which may be one of the main drawbacks to their use in food. Arai el al. [90] showed that the bitterness of peptides from soybean protein hydrolysates was reduced by treatment of Aspergillus acid carboxypeptidase from A. saitoi. Significant amounts of free leucine and phenylalanine were liberated by Aspergillus carboxypeptidase from the tetracosapeptide of the peptic hydrolysate of soybean as a compound having a bitter taste. Furthermore, the bitter peptide fractions obtained from peptic hydrolysates of casein, fish protein, and soybean protein were treated with wheat carboxypeptidase W [91], The bitterness of the peptides lessened with an increase in free amino acids. Carboxypeptidase W can eliminate bitter tastes in enzymatic proteins and is commercially available for food processing. 

Elimination of Bitterness of Bitter Peptides by Squid Liver Carboxypeptidase... 

Molecular and enzymatic properties of serine carboxypeptidase (EC.3.4.1.6.1, CPase Top), isolated and refined from the common squid (Todarodes pacificus) liver, were studied. It was found that this enzyme reacts well at the C-terminal position of peptides having hydrophobic amino acids. Because of this property, it was anticipated that this enzyme would have the effect of eliminating bitterness of some peptides. This enzyme was used on bitter peptides prepared by hydrolysis of proteins with pepsin and trypsin. It was found that this CPase Top can eliminate bitter peptides prepared from soy protein and com gluten. 

Methods for eliminating bitter peptides in partial protein hydrolysates are known, but they cause a significant loss of essential amino acids. These procedures usually include additional enzymatic hydrolysis under controlled conditions (a shorter time for the hydrolysis leads to higher peptides that are not bitter) and a selection of suitable proteases, such as aminopeptidases, carboxypeptidases and some other proteases. Enzymes of plant and microbial origin have been successfully used for this purpose. For example, the intracellular peptidases from Lactococcus lactis ssp. cremoris and Brevibacterium linens, which have high proteolytic activity, successfully hydrolyse bitter peptides in cheeses. 

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