The application of extremely low-frequency (elf) magnetic fields to accelerate growth of Lactobacillus acidophilus bacteria and milk fermentation process

The fermentation process for a long time makes the nutritional content of milk decrease due to spoilage. One of the causes is the growth of pathogenic bacteria in milk. Lactobacillus acidophilus bacteria proved to be effective as an antibacterial pathogen. This study aims to determine the magnetic flux density ((MFD) and exposure time that makes the optimum growth of Lactobacillus acidophilus bacteria and its effect on fermented milk's lactic acid content and pH. The research sample was Lactobacillus acidophilus bacteria grown in cow's milk. The exposure given tused a time-changing magnetic field (MF) with a frequency of 50 Hz and a MFD of 0.1 mT, 0.2 mT, and 0.3 mT for 5-25 minutes, respectively. The results show that the optimum bacterial growth occurs in samples exposed to a MFD of 0.2 mT for 5 minutes. Meanwhile, inhibition of bacterial growth begins on the exposure to a MFD of 0.3 mT for 15 minutes. Moreover, it is found that the highest lactic acid content and the lowest pH are obtained in exposed milk with a MFD of 0.2 mT for 5 minutes. Lactic acid content and pH are closely related to the number of Lactobacillus acidophilus bacteria colonies present in milk