Vibration-induced particle formation during yogurt fermentation — Industrial vibration measurements and development of an experimental setup

• Oscillation measurements on an industrial yogurt production line
• Industrial yogurt samples showed differences despite constant process conditions.
• Development of an experimental setup to study the effect of oscillations
• Number of large particles increased by a factor of 2.4 due to sonication at pH 5.4.

The aim of the study was to investigate the effects of vibrations during yogurt fermentation. Machinery such as pumps and switching valves generate vibrations that may disturb the gelation by inducing large particles. Oscillation measurements on an industrial yogurt production line showed that oscillations are transferred from pumps right up to the fermentation tanks. An experimental setup (20 L) was developed to study the effect of vibrations systematically. The fermenters were decoupled with air springs to enable reference fermentations under idle conditions. A vibration exciter was used to stimulate the fermenters. Frequency sweeps (25–1005 Hz, periodic time 10 s) for 20 min from pH 5.4 induced large particles. The number of visible particles was significantly increased from 35 ± 4 (reference) to 89 ± 9 particles per 100 g yogurt. Rheological parameters of the stirred yogurt samples were not influenced by vibrations.

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