Purpose: The objective of this study was to further investigate the antimicrobial effects of carvacrol (the main ingredient in oregano oil widely used as a salad dressing) and cinnamaldehyde (a major food flavoring agent) incorporated apple, carrot and hibiscus-based edible films against P. fluorescens in bagged organic lettuce.
Methods: Romaine or iceberg lettuce samples were washed, dip inoculated with P. fluorescens (107 CFU/ml) and dried. Each sample (10 g) was put into a Ziploc® bag. Edible films pieces (0.3 g) were then added into the bag and mixed well. The bags were sealed and stored at 4°C. Samples were taken at day 0, 3, and 7 for enumeration of survivors.
Results: On romaine and iceberg lettuce, 3% carvacrol films showed the best inhibiting effects against Pseudomonas. At day 0, the populations were reduced 2.2-2.3, 2.6-4.3, and 2.3-2.6 log CFU/g by 3% apple, carrot and hibiscus films, respectively. Films with 1.5% carvacrol decreased the population by 1-1.5 log CFU/g at day 7. The 3% cinnamaldehyde films showed 0.7-1.3, and 1.7-3.0 log reductions on romaine and iceberg lettuce, respectively. Films containing 1.5% cinnamaldehyde reduced Pseudomonas population by 0.4-1.3 log CFU/g. In general, carvacrol films were more effective than cinnamaldehyde films. Edible films showed better inhibiting effects on iceberg than on romaine lettuce.
Significance: This study demonstrates the potential of edible films incorporated with carvacrol and cinnamaldehyde to inhibit P. fluorescens on organic lettuce. These antimicrobial edible films could provide the organic fresh produce industry with additional options to control the spoilage microorganisms and assure quality.