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The effect of micellar casein concentrate purity on sulfur/eggy flavor in UHT milk protein-based beverages.

D. Whitt


The effect of micellar casein concentrate purity on sulfur/eggy flavor in UHT milk protein-based beverages.
D. Whitt*1, B. G. Carter1, D. M. Barbano2, M. A. Drake1. 1North Carolina State University Raleigh, NC, 2Cornell University Ithaca, NY.

Micellar casein concentrate (MCC) is made by removing serum proteins (SP) from skim milk by microfiltration (MF). Milk SP denature during thermal processing and are the source of volatile sulfur/eggy off-flavors (H2S and C2S). Our objective was to determine the amount of milk derived whey protein (MDWP) removal (i.e., SP) required to eliminate sulfur/eggy flavor in milk protein beverages at 15 g protein / 240 mL serving. MCC with 95% MDWP removal was produced from skim milk (50°C) using a 3X, 3-stage ceramic MF process using 0.1 µm pore size graded permeability membrane. Model beverages with carrageenan, cellulose gum, and dipotassium phosphate were created by adding MDWP back into the MCC to simulate 4 levels of MDWP removal: 95.2%, 91.0%, 83.2%, and 69.2% which correspond to MCC purities (i.e., casein % of true protein) of 93.8, 93.2, 92.2 90.2%, respectively. Beverages were ultrapasteurized (UHT) by direct steam injection (140°C for 2.3 s), bottled and cooled (4°C). Residual SP and MCC purity were measured by Kjeldahl before UHT. Beverages were profiled by descriptive analysis and analyzed by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) for sulfur volatiles (H2S, C2S). The H2S concentrations were 9.3d, 21.9c, 35.4b, 58.6a ppb and C2S were 33.3d, 58.5c, 100.7b, 148.8a ppb (P < 0.05) for beverages corresponding to 95.2, 91.0, 83.2, and 69.2% MDWP removal, respectively. The residual MDWP concentrations increased (0.40d, 0.44c, 0.51b, and 0.63a g/100 g beverage), as milk serum protein removal % decreased. Sensory perception of sulfur/eggy flavor intensity increased with increasing level of residual SP (P < 0.05). Concentrations of H2S and C2S were below documented threshold values, and sulfur/eggy flavors were not detected by the trained panel in the MCC with 95% serum protein removal. Serum protein removal from MCC must be greater than 91% to achieve a product with no sulfur off-flavors following thermal processing. To eliminate sulfur eggy flavor in a milk protein beverage at 15 g protein and 0.35 g fat per 240 mL serving, the residual SP concentration needs to be <0.96 g/240 mL beverage.

Keywords: micellar casein, purity, protein beverages.

Biography: Daniel is completing his Master's degree in Food Science at North Carolina State University under the guidance of Dr. MaryAnne Drake.