Edible film may kill bacteria in refrigerated foods
Antimicrobial edible films and coatings have received attention since they have a good potential to delay microbial spoilage of food and to reduce the risk of surface contamination of food by microorganisms.
According to the researchers, incorporation of biopreservatives, especially bacteriocins and antimicrobial enzymes, as well as plant extracts into edible films have gained significant interest in the food industry due to their greater acceptance by the increasing number of consumers seeking ‘natural’ products.
The authors of the study said that the enzyme, LPS, which is often used to improve the microbial quality of milk and cheese, has a broad antimicrobial spectrum, and they added that the concept of using the enzyme in antimicrobial packaging is quite novel.
Stability
They said that LPS binds and immobilizes effectively onto films following cross-linking and it shows appropriate stability and activity at a broad temperature and pH range.
In this research project, the antimicrobial activity of LPS incorporated into alginate films and its components was tested on different bacteria including E. coli, Listeria innocua, and Pseudomonas fluorescens in the presence of different concentrations of H2O2 (0.2, 0.4, and 0.8 millimoles (mM) and KSCN (1, 2, and 4 mM), explained the scientists.
The specific objectives of this research, they said, were to determine the effective concentrations of LPS components against the test bacteria.
Results
The study showed that the antimicrobial activity of the LPS system on target bacteria changed according to the concentrations of KSCN and H2O2.
The scientists said that the results indicated that the growth of all tested bacteria was prevented for a six hour period through application of the LPS system in the presence of 0.4 or 0.8mM H2O2 and 4mM KSCN.
They added that growth of pathogens L. innocua and P. fluorescens was inhibited during a 24 hour incubation period in the presence of 0.8mM H2O2 and 4mM KSCN; however E. coli growth could not be restrained for 24 hours under the same conditions.
The researchers maintain that with 0.2 mM H2O2 and 1 to 4 mM KSCN, a considerable inhibitory effect was obtained only on P. fluorescens, with the decreasing order of the resistance of studied bacteria to the LPS system as follows: E. coli, L. innocua, and P. fluorescens.
The authors concluded that the duration of the antimicrobial effect of the developed LPS system would be extended when the alginate films are applied to refrigerated foods.
Source: Food Microbiology and SafetyPublished online ahead of print - doi: 10.1111/j.1750-3841.2009.01057.x Title: Antimicrobial Activity of Lactoperoxidase System Incorporated into Cross-Linked Alginate FilmsAuthors: F. Yener; F. Korel; A. Yemenicio˘glu.
