Both sides of the same sampleswere inoculated with 100 μL of E. coli
through spot inoculation (8–10 drops) and were let for 1 h from each
side to achieve bacterial attachment. The challenge tests were carried
out on 6 pieces of lettuce leaves, resulting in a total inoculated area of
192 cm2. After inoculation, lettuce leaves were placed into an empty
sterilized beaker, filling it with 500 mL of sterilized water