17B-17 |
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T. K. SINGH1, N. D. Young2, M. A. Drake2, and K. R. Cadwallader1. (1) Dept. of Food Science & Human Nutrition, Univ. of Illinois, Urbana-Champaign, 1302 W. Pennsylvania Ave., 202 Agricultural Bioprocess Lab., Urbana, IL 61801, (2) Dept. of Food Science, North Carolina State Univ., Schaub Hall, Box 7624, Raleigh, NC 27695-7624 Bitterness is a problem in various cheeses and has been associated with the production of bitter peptide(s). Several peptides have been isolated from different cheese varieties and linked to bitter taste but previous studies have lacked a detailed sensory characterization. The peptide b-casein fragment 193-209 (b-CN f193-209), produced by chymosin action on b-casein (b-CN), has been widely reported as the major cause of bitterness in cheeses. The objective of this study to was to isolate and purify b-CN f193-209 and to perform detailed sensory analysis on this peptide in different matrices. For the production of b-CN f193-209, an aqueous solution of purified b-CN was hydrolyzed by chymosin (5-7 h at 30oC). The b-CN f193-209 was isolated by adjusting pH of the mixture to 4.6. At pH 4.6, b-CN and the larger peptide b-CN f1-192 were precipitated leaving only b-CN f193-209 in solution, which was concentrated by freeze-drying. The purity of the peptide was assessed by RP-HPLC followed by characterization using N-terminal amino acid sequence and mass analysis. Taste detection thresholds of the peptide in water, skim milk, whole milk, and cheese were determined by 6-series ascending forced choice threshold analysis. Subsequently, the peptide was incorporated into milk and cheese at concentrations above detection thresholds and descriptive sensory analysis was conducted using a trained panel. Purity of the peptide was >98%. The mass of the peptide was 1882.51 Dalton which coincided with the expected mass of b-CN f193-209. N-terminal analysis confirmed that the peptide started at residue 193 on the published sequence of b-CN. Detection thresholds were 0.02, 0.06, and 0.89 % (w/w) for water, milk, and cheese, respectively. Descriptive sensory analysis confirmed that the peptide exhibited bitter taste which increased with increasing concentrations; with minimal other flavors or tastes detected. The b-CN f193-209 can contribute to bitterness in cheeses.
Session 17B, Dairy Foods: General
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