微生物与生化技术杂志

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Influence of Certain Pulsed Electric Field Conditions on the Growth of Lactobacillus acidophilus LA-K

Cueva O and Aryana KJ

Pulsed Electric Field (PEF) processing involves the application of pulses of electricity, for less than one second to fluid products placed between two electrodes. Lactobacillus acidophilus is an important probiotic bacterium used for the production of fermented dairy foods. The objective was to study the influence of electric pulse period, electric field strength, and electric pulse width on the growth of Lactobacillus acidophilus LA-K. Lactobacillus acidophilus LA-K, suspended in sterile peptone water was treated using an OSU-4 PEF processor. The treatments were pulse periods of 10,000, 20,000 and 30,000 μs electric field strength of 5, 15 and 25 kV/cm, and pulse widths of 3, 6 and 9 μs. Growth was determined hourly for 16 hours of anaerobic incubation at 37°C. Pulse period had a significant (p=0.0017) influence on the growth. There were no significant differences among the control, 30,000 μs and 20,000 μs. The growth of Lactobacillus acidophilus subjected to the pulse period of 10,000 μs was significantly lower than the growth of the control, and the growth when subjected to 30,000 μs. Electric field strength had a significant (p<0.0001) influence on the growth. Growth subjected to 15 and 25 kV/cm was significantly lower than the control and 5 kV/cm. There were no significant differences between the control and 5 kV/cm. There were no significant differences between the growth, when Lactobacillus acidophilus was subjected to 15 and 25 kV/cm. Bipolar pulse width effect had a significant (p<0.0001) influence on the growth. Growth of the control was significantly higher than the growth of Lactobacillus acidophilus subjected at any of the bipolar pulse widths studied. There were no significant differences in growth among the three different bipolar pulse widths. Electric field strength significantly influenced growth of Lactobacillus acidophilus LA-K. Bipolar pulse width and pulse period slowed log stage growth of Lactobacillus acidophilus LA-K. Slower growth of adjunct bacteria can sometimes be good in the manufacture of cultured dairy foods, as it results in controlled release of bacterial enzymes for improved flavor and texture development.