Purpose: The major objective of this study was to evaluate the efficiency of pulsed light on inactivating Escherichia coli K12, a biological indicator of unsanitary processing conditions, on hard-cooked eggs.
Methods: Hard-cooked eggs inoculated with E. coli K-12 (MDD 333) were positioned 5.5 cm and 9.5 cm away from the quartz window of a PL system (LH840-LMP-HSG) and treated from 1 to 30 s. Initial and survivor counts were determined by: standard plate counting (SPC) on tryptic soy agar supplemented with Rifampicin (80 μg/ml) and most probable number (MPN) for counts falling below 25 CFU/ml for SPC. Temperature was monitored during treatment in addition to color and texture determined by the CIELAB system and texture profile analysis respectively. Each experiment was conducted in triplicate and statistical analysis was conducted using Analysis of Variance.
Results: Significant reductions (P < 0.05) on E. coli K-12 populations were achieved after PL exposure. Maximum inactivation (6.4 ± 0.0 log CFU/egg) was attained after 20 s and 30 s treatment at 5.5 cm and 9.5 cm from the quartz window, respectively. Likewise, temperature increased significantly (P < 0.05) up to 8.8 ± 0.9 °C and 5.6 ± 0.6 °C after 30 s treatment at 5.5 cm and 9.5 cm distance, respectively. No significant differences (P> 0.05) were observed in color or texture post PL treatment.
Significance: The findings of this study suggest that PL can enhance the safety of hard-cooked eggs and contribute to minimize the risk associated with RTE foods.