Graduate Thesis Or Dissertation
 

Identification of Bitter Peptides in Aged Cheddar Cheese

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/1n79hd04g

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  • Bitterness is a common flavor attribute of aged cheese, but excessive levels are a flaw leading to consumer rejection. Bitterness in cheese has been primarily associated with milk casein-derived peptides of medium size (500–3,000 Da) and relative hydrophobicity. Herein, we demonstrate a novel approach for the identification of bitter peptides in cheese. Crossflow filtration was applied to isolate 500–3,000 Da peptides from 14 commercial Cheddar cheeses ranging in age from 0.2–8.7 years and representing non-bitter and bitter samples. The bitterness intensity of the samples was determined by a trained sensory panel, leading to the categorization of the samples into threshold and low (non-bitter) and moderate and extreme (bitter) groups. The peptide profile of the 500–3,000 Da fractions was determined by mass spectrometry-based peptidomics, revealing over 2,000 peptides. Linear regression and standard mean difference analyses were applied to identify peptides most strongly correlated with the bitter cheeses. A mean analysis of the two rankings was performed to identify the top 12 peptides with the strongest likely association with bitterness, based on their rank order. Selected bitter peptide candidates were synthesized, and their bitterness was assessed by a trained sensory panel indicating five of the 12 peptides, YPFPGP (β-casein [60–65]), YPFPGPIPN (βA2-casein [60–68]), LSQSKVLPVPQKAVPYPQRDMPIQA (β-casein [165–189]), YPFPGPIHNS (βA1-casein [60–69]) and its serine phosphorylated version YPFPGPIHN[S] (βA1-casein [60–69]) peptides, as bitter. Applying peptidomics and statistical screening tools, rather than traditional chemical separation techniques, to identify bitter peptides allows for screening the whole peptide profile. In the future, this data can be combined with the microbial and protease profile of the Cheddar samples to help understand how these factors contribute to bitter taste development.
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