Many food products such as yogurt and kefir are fermented from milk. The products contain suspended particles, including aggregates. Kefir and yogurt are dynamic, since the probiotic enzymes responsible for the fermentation are in the product until consumption. The distribution of the culture particles can change with time and location in the containment vessel. These particles affect appearance and texture, both important quality attributes.
A team working in the Laboratory of Professor Paweł L. Urban at the National Chiao Tung University (Hsinchu, Taiwan) developed a capillary hydrodynamic chromatography apparatus using three identical capillaries for spatial and temporal analysis of fermented dairy products using an ActiPix D100 UV imaging detector (Paraytec Ltd., York, UK) (reference: Tang, Y.R.; Huang, H.Y. et al. Capillary hydrodynamic chromatography reveals temporal profiles of cell aggregates. Anal. Chim. Acta 2016, 910, 75–83).
The capillaries sample simultaneously from the top, center, and bottom of the culture vial. The three-minute chromatograms covering 30 hours of culture of milk clearly show the formation of intermediate aggregates. Collected peaks were also imaged offline with a vertical optical microscope. These confirm the formation of larger aggregates, especially for kefir, as the fermentation progressed.
Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected].
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