Acid Tolerance of Lactobacillus acidophilus LA-K as Influenced by Various Pulsed Electric Field Conditions

Abstract

Lactobacillus acidophilus has several health benefits and is used as an adjunct bacterium in the manufacture of cultured dairy foods. Bile tolerance is an important probiotic characteristic. Pulsed electric field (PEF) processing is non-thermal, hurdle technology which comprises of passing fluid foods between two electrodes and subjecting them to pulses of voltage for less than one second. Whether certain mild PEF conditions can enhance bile tolerance of Lactobacillus acidophilus is not known. The objective was to study the influence of certain PEF conditions on the, bile tolerance of Lactobacillus acidophilus LA-K. Lactobacillus acidophilus LA-K suspended in sterile peptone 0.1% w/v distilled water was treated with pulse widths of 3, 6 and 9 s, pulse periods of 10,000; 20,000 and 30,000 s and electric field strengths of 5, 15 and 25 kV/cm. The control did not receive any pulsed electric field condition. Bile tolerance was determined hourly for 16 hours. PROC GLM of the Statistical Analysis Systems (SAS) was used for data analysis. Significant differences were determined at P<0.05. Three replications were conducted. Bipolar pulse width effect had a significant ( p<0.0001) influence on the bile tolerance. Bile tolerance of the control was significantly higher than the bile tolerance subjected to any of the bipolar pulse widths studied. There were no significant differences among the three different bipolar pulse widths. Pulse period had a significant ( p<0.0001) influence on the bile tolerance. The control and the three different pulse periods studied were significantly different from each other. The bile tolerance of the control was significantly the highest, followed by the bile tolerances subjected to 30,000 s and 20,000 s respectively. The bile tolerance subjected to 10,000 s was significantly the lowest. Electric field strength had a significant ( p<0.0001) influence on the bile tolerance. Bile tolerance of the control and bile tolerance of Lactobacillus acidophilus LA-K subjected to 5 kV/cm were signifycantly the highest while the bile tolerance when subjected to 25 kV/cm was significantly the lowest.