Bitterness is a common flavor attribute of aged cheese associated with the peptide fraction, but excessive levels are a defect leading to consumer rejection. Bitterness in cheese has been primarily associated with peptides that arise from the breakdown of casein. The last review of bitter peptides was published in 1992. This updated review compiled information about the bitter peptides published up to 2022. Our comprehensive search of the literature compiled 226 peptides associated with bitterness and cheese protein origins into a database (Supplemental Materials). The influences of a peptide's physical properties, such as molecular weight, average hydrophobicity, peptide length, number of prolines and the presence of hydrophobic amino acids in the peptide's terminus, were assessed for correlation with bitterness threshold values this assessment found that, among variables considered, higher molecular weight had the strongest correlation with higher bitterness among known peptides. Heatmaps of bitter peptides and their bitterness threshold values highlight β-casein as the primary source of known bitter peptides in cheese. This comprehensive database of cheese protein-derived bitter peptides and this discovery of the correlation of a peptide's physical properties to bitterness will aid future researchers in the identification and discovery of contributors to cheese bitterness.
Keywords: bitter cheese; bitter peptides; bitterness threshold values; cheese flavor; molecular weight; sensory analysis.