Bitter taste of enzymic hydrolysates of casein

Abstract

beta-Casein A2 was isolated from milk of a homozygous cow and hydrolysed with trypsin. The hydrolysate was separated by RP-HPLC into 18 peptides, all but one of which could be attributed to the sequence of beta-casein on the basis of the amino acid composition. Some peptides overlapped. In total, they represented about 97% of the protein sequence. Only three peptides had a bitter taste, namely I49-N68 (recognition threshold 1.0 mg/ml, 0.45 mmol/l), I49-K97 (1.5 mg/ml, 0.28 mmol/l) and G203-V209 (0.175 mg/ml, 0.23 mmol/l). The contribution of the three peptides to the overall bitterness of the beta-casein hydrolysate (2.67 mg/ml) was about 11, 21, and 60%, respectively. Peptide I49-K97 was present in the hydrolysate together with its fragments I49-N68 and S69-K97. Remarkably, the smaller and more hydrophobic fragment I49-N68 was less bitter than I49-K97 on a molar basis, whereas the larger and more hydrophilic fragment S69-K97 had a neutral taste. These results show that in the case of larger peptides neither hydrophobicity nor size are responsible alone for bitter potency, but that conformational parameters must be of great importance. Furthermore, it can be concluded that only a part of the structure is responsible for the contact with the receptor. The bitterness of G203-V209 is discussed in connection with related synthetic peptides in the literature.

Degradation of a Bitter Peptide Derived from Casein by Lactic Acid Bacterial Peptidase

“…According to Bumberger & Belitz (1993), it accounted for 3.92% of the total tryptic digest of β-casein, and its percentage contribution to the total bitterness of the hydrolysate was 59.8%. This bitterness was the strongest in the tryptic digest of β-casein.…”

“…It was generated by tryptic digestion of β-casein (Bumberger & Belitz, 1993). Although we initially tried to isolate the peptide from the tryptic digest of β-casein, it was difficult to obtain a sufficient amount of the peptide for the degradative activity assay.…”

“…Several studies have focused on the characterisation of bitter peptides and the elucidation of formation mechanisms (Habibi-Najafi & . The main bitter peptides derived from β-casein found thus far have been documented by Bumberger & Belitz (1993). Attempts have been made to debitter bitter peptides (Raksakulthai & Haard, 2003).…”

Debittering of Enzymatic Hydrolysate Using Exopeptidase Active Fractions from the Argentina Shortfin Squid Illex argentinus Hepatopancreas

“…GF-I fraction casein hydrolysate HPLC pro- Table 3 GF-I fraction casein hydrolysate casein peptide peptide peptide . , Bumberger and Belitz (1993), Park and Lee (1996), Lin et al (1997), Nishiwaki et al (2002) exopeptidase casein , C18-RP HPLC profile retention time 30 peak 30 peak .…”

“…Trypsin casein hydrolysate (Matoba et al, 1970a(Matoba et al, , 1970bBumberger and Belitz, 1993 ;Tan et al, 1993) …”