Antimicrobial Effect of Sanitizing Solutions on Fresh Romaine Lettuce

Recently the consumption of fresh produce has increased due to the desire of people to have healthy lifestyles. Fresh produce is more susceptible to be contaminated with pathogens during processing. Washing is one of the most convenient treatments used to reduce microbial loads. Generally, people wash with water. However, water is unable to combat bacteria such as Escherichia coli. The main objective of this experiment is to study the effect of different sanitizing solutions on the microbial growth reduction on lettuce. Fresh lettuce leaves were inoculated with E. coli inoculum and stored at room temperature for 3 h/refrigerated temperature for 24 h. The inoculated leaves were soaked in different sanitizing solutions: sodium hypochlorite (SH), acidified sodium chloride (ASC), and peroxyacetic acid (PAA) with similar ppm and water for 1 min, 3 min, and 5 min respectively. Plate count method was used to compare the microbial growth with and without treatment. All the experiments were performed under sterile conditions and repeated three times. The results showed that there was an increase in E. coli growth during storage of inoculated samples at room temperature by 2.15 log CFU/g but no significant increase in growth found in samples kept at the refrigerated condition. On comparing the washing with water and all sanitization solution, it was found that water could maximum reduce up to 1.2 log CFU/g, whereas PAA could reduce 4.07 log CFU/g at 5 min. In conclusion, PAA was the most effective and alternate safe washing solution, other than chlorine, for decontamination of fresh lettuce.