Acid Tolerance of <i>Lactobacillus acidophilus</i> LA-K as Influenced by Various Pulsed Electric Field Conditions
- 1 School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, USA
- 2 Department of Food Science, Louisiana State University Agricultural Center, Baton Rouge, USA
Abstract
Pulsed electric field (PEF) processing involves the application of pulses of voltage for less than one second to fluid foods placed between two electrodes. Lactobacillus acidophilus is an important probiotic bacterium used for the production of fermented dairy products. Acid tolerance is an important probiotic characteristic. The influence of PEF on acid tolerance of Lactobacillus acidophilus is not known. Objective of this study was to elucidate the influence of certain PEF conditions on the acid tolerance of Lactobacillus acidophilus LA-K. Freshly thawed Lactobacillus acidophilus LA-K was suspended in sterile peptone 0.1% w/v distilled water and treated in a pilot plant PEF system. The treatments were pulse width (3, 6 and 9 μs), pulse period (10,000; 20,000 and 30,000 μs) and voltage (5, 15 and 25 kV/cm). Control was run through PEF system at 60 mL/min without receiving any pulsed electric field condition. Data were analyzed using the PROC GLM of the Statistical Analysis Systems (SAS). Differences of least square means were used to determine significant differences at P < 0.05. The control and the three different bipolar pulse widths studied were significantly different from each other. The acid tolerance of the control was significantly the highest, followed by the acid tolerance of the culture subjected to 3 μs and 6 μs. The acid tolerance of culture subjected to 9 μs was the lowest. The acid tolerance of the control was significantly the highest, followed by the acid tolerances subjected to the pulse period of 30,000 and 20,000 us. The acid tolerance of culture subjected to pulse period 10,000 μs was significantly the lowest. The acid tolerance of the control was significantly the highest followed by the acid tolerances of culture subjected to electric field strength of 5 and 15 kV/cm. The acid tolerance of culture subjected to 25 kV/cm was significantly the lowest. Acid tolerance of Lactobacillus acidophilus LA-K lowered by increasing pulse widths and voltages but lowering pulse periods.
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