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

BACKGROUND The long fermentation process makes the nutritional content of milk decrease due to spoilage. One of the causes of spoilage is the growth of pathogenic bacteria in milk. In regard to this, Lactobacillus acidophilus bacteria have proven effective as an antibacterial pathogen. This study aims to determine the magnetic flux density (MFD) and exposure time that result in the optimum growth of Lactobacillus acidophilus bacteria and their effect on fermented milk’s lactic acid content and pH. METHODS The research sample was Lactobacillus acidophilus bacteria grown in cow’s milk. The exposure given used 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 0–25 minutes, respectively. RESULTS The results showed that the optimum bacterial growth occurred in samples exposed to a MFD of 0.2 mT for 5 minutes. Meanwhile, inhibition of bacterial growth began on the exposure to a MFD of 0.3 mT for 15 minutes. Moreover, it was found that the highest lactic acid content and the lowest pH were obtained in exposed milk with a MFD of 0.2 mT for 5 minutes. CONCLUSIONS Lactic acid content and pH were closely related to the number of Lactobacillus acidophilus bacteria colonies present in the milk.