New approaches are therefore needed to elucidate the structural features associated with bitterness CDK phosphorylation of amino acids and peptides, and to devise strategies to reduce the bitter sensation, including spray-drying encapsulation with maltodextrin and cyclodextrin as carriers [53], addition of bitter masking or inhibiting ingredients [54●], or enzymatic exopeptidase treatment [55]. Sensory-guided fractionation,

involving multi-step separations followed typically by mass spectrometry and ‘sensomics mapping’, is a recognized approach to identify the peptide sequences responsible for undesirable bitter taste of protein hydrolysates and their fractions [47], but requires evaluation by humans to verify the taste of individual peptides in the isolated fractions buy SCH772984 or chemically synthesized peptides. Not only is this a time-consuming and expensive process, there are technological challenges related to the small quantities of peptides typically available, as well as safety concerns for taste evaluation considering the non-food grade solvents and chemical reagents used in peptide

synthesis, fractionation and purification. Panelist fatigue, the limited number of samples that can be evaluated at a time, and difficulty with standardization particularly over long periods of time are also important considerations. QSAR may be useful to complement human sensory evaluations by providing clues to elucidate the bitterness of food-derived bioactive peptides 24•, 25, 56, 57 and 58, but, as previously mentioned, the validity and usefulness of the QSAR approach hinges on the information available for building the prediction model. Although human sensory evaluation will always be the ‘gold standard’ for assessing taste attributes and acceptability, in view of the aforementioned limitations, there has been increasing interest to develop instrumental taste sensing systems and electronic tongues for screening of large numbers of fractions and samples,

thus lightening the burden of human taste panel evaluation 59 and 60. Instrumental sensors have been applied to analyze taste of amino acids, pheromone peptides and protein hydrolysates 61, 62, 63 and 64••, and to assist in screening for compounds to mask their bitterness [65]. Cell based assays also show promise as an alternative to human panelists for screening of peptides for bitter taste. Using engineered cell lines expressing the TAS2R and the chimeric G protein α-subunit (Gα16gust44), positive interaction of peptides with the TAS2R receptor is detected fluorometrically by an influx of extracellular calcium indicator that is taken to represent activation by bitter peptides [51●].