Problems and Opportunities of Natural Antimicrobials
Natural antimicrobials are gaining interest by consumers for their uses as alternatives to traditional antimicrobial treatments due to their “green” nature. There is a big market of using natural antimicrobials in foods. However, there are many limitations in the application of natural antimicrobials in foods. It requires further research on their antimicrobial efficacy, consumer acceptability, and cost. There are several challenges of using naturally derived antimicrobials in food, including:
- 1. Hydrophobic antimicrobials have low solubility in the aqueous phase, at which concentration they are not able to function their bioactivities.
- 2. Essential oils, which have been investigated widely in the past several years as natural antimicrobials, are very volatile, and therefore a large amount may be lost during food processing, causing the increased cost.
- 3. Some sensitive compounds degrade during the manufacturing, storage, transportation, and utilization, such as thermal processing, UV radiation, pH adjustment, and enzyme digestion, resulted in the loss of antimicrobial activity.
- 4. Further, the addition of some natural substances can lead to adverse changes in the sensory properties of foods, such as herbs and essential oils. When applied at the concentrations needed to achieve the desired level of antimicrobial potency, these antimicrobials can adversely affect the organoleptic properties of food beyond its threshold and consumer acceptance.
Even though many of the natural antimicrobials are categorized as GRAS for food application, their use in commercial applications requires regulatory approval. Natural antimicrobials can provide a tremendous opportunity for advancing the field of food preservation and safety; however, additional research is needed to optimize their applications.
The challenge of using these natural antimicrobials as preserving agents may be overcome to some extent by nanoencapsulation instead of applying them as free antimicrobials directly to the food. By loading antimicrobials into nanoparticles/formulations, the physical properties such as dispersibility, dispersion stability, turbidity, viscosity can be significantly improved, and hence the bioactivities including antimicrobial activity can be promoted in contrast to the free antimicrobials (Blanco-Padilla et al., 2014). Nanoencapsulation may also be helpful to protect the encapsulated antimicrobials from degradation during processing and storage, mask unpleasant flavors, and release the antimicrobials at a controlled rate. Moreover, some designed nanocarriers can trigger the release of antimicrobials according to the environment surrounding the food systems (pH, temperature, etc.). These functions are typically enabled by incorporating the encapsulated antimicrobials into fibers, or coatings/films.