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Journal of Dairy Science Vol. 83 No. 2 275-277
© 2000 by American Dairy Science Association ®
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Organic Acids and Volatile Flavor Components Evolved During Refrigerated Storage of Kefir

Z. Guzel-Seydim 1, A. C. Seydim 2, and A. K. Greene 1

1 Department of Animal & Veterinary Sciences, Clemson University, Clemson, SC 29634-0361
2 Department of Food Science and Human Nutrition, Clemson University, Clemson, SC 29634-0361

Kefir samples were prepared and transferred to sterile jars for storage at 4°C. After 0, 7, 14, and 21 d of storage, the pH, organic acid, and volatile flavor component content were determined to monitor possible flavor changes during storage. Stored samples were analyzed for organic acid (orotic, citric, pyruvic, lactic, uric, acetic, propionic, butyric, and hippuric) content by HPLC with UV detection at 275 nm. Acetoin, ethanol, acetaldehyde, and diacetyl were monitored using gas chromatography equipped with a headspace autosampler. There was no significant decrease in average pH of samples between d 0 and 21 of storage (P > 0.05). Lactic acid concentration increased during storage, reaching a maximum of 7739 ppm by d 21. Orotic and citric acids increased slightly during storage. Although pyruvic and hippuric acids are produced during fermentation, neither was detected during storage. Acetic, propionic, and butyric acids were not detected during kefir storage. Ethanol concentrations increased during storage and reached 0.08% by d 21. The amounts of acetaldehyde and acetoin, common flavor substances in many cultured dairy products, increased during fermentation. Acetaldehyde content in kefir samples doubled from d 0 to 21, reaching a final concentration of 11 µg/g. During storage, the concentration of acetoin decreased from 25 ppm on d 0 to 16 ppm on d 21. However, diacetyl, another common flavor component in cultured dairy products, was not detected during fermentation or storage.

Key Words: kefir • organic acids • volatile flavor components • refrigerated storage

Submitted on May 19, 1999
Accepted on September 20, 1999




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