71A-54 |
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S. L. Barron1, J. E. BOCK1, and K. A. Schmidt2. (1) Dept. of Animal Science and Industry, Kansas State Univ., 160 Call Hall, Manhattan, KS 66506, (2) Food Science Institute, Kansas State Univ., 224 Call Hall, Manhattan, KS 66506 Milk is a complex beverage possessing a unique flavor comprised of hundreds of aldehydes, ketones, acids, sulfides, and alcohols. Over time, certain volatile compounds may change in concentration, thereby changing the milk flavor profile. Some flavor changes occurring during normal shelf-life are undesirable and may discourage milk consumption. Our objective was to identify compounds and their concentrations that contribute to flavor changes throughout milk shelf-life. Milks of 3.3% and 2% fat contents were obtained immediately after production, stored at 4 °C, and analyzed initially and weekly thereafter for total aerobic counts, pH, and chemical composition via standard methods. Also, volatile compound concentrations were measured with SPME-GC headspace analysis. End of shelf-life was determined at a total aerobic count of 107 cfu/mL, pH of 6.4, or 43 days, whichever resulted first. Three replications were conducted and analyzed separately. Overall, milks had a shelf-life of 29 days, with a lowered pH being the most prevalent indicator of shelf-life end. Seventy-five to 100 peaks were detected from each chromatogram, but only the following peaks were found, identified, and quantified in both milk samples throughout the sampling time: benzaldehyde, 2-butanol, hexanal, 2-heptanal, 2,3 butanedione, ethyl caproate, and pentyl furan. Hexanal and 2-butanol decreased in concentration by 60 to 75% and 40 to 50% by days 15 and 8, respectively, and then concentrations doubled by shelf-life end. Benzaldehyde and 2-heptanal concentrations increased significantly after day 22. 2,3 Butandione concentration increased from day 15 to day 29 by 70 to 90%. Milks from the three replications had varying microbial counts and pH values as a function of time, despite having similar values at day 1. This may explain differences in flavor profiles and compound concentrations between replications. The chemical composition of milk undergoes significant changes as a result of time, and thus contributes to milk flavor.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |