Preservatives are necessary to decrease deterioration of products and the risk of infection to consumers, but can be limited and unsafe themselves. Certain plant-derived essential oils can be used as preservatives with lower toxicity levels than their synthetic counterparts.
The use of preservatives allows for greater product shelf life and decreased risk of infection for consumers. However, current preservatives are mainly synthetic and have their limitations. Many are only effective within certain pH ranges, only affect certain microorganisms, have unfavourable smells or tastes, or are inherently unsafe themselves. These concerns have caused researchers to seek natural, healthy alternatives to synthetic preservatives.
Certain essential oils have shown preservative properties, though only three essential oil based products currently exist. Parts of essential oils have broad-spectrum antimicrobial characteristics. Most importantly, essential oils have low toxicity in comparison to synthetic preservatives and are easily biodegradable. The overall toxicity of essential oils remains an important factor to study.
Hernandes et al. evaluated the efficacy and safety of Lippia origanoides essential oil as a preservative in industrial products. The Lippia family of plants is noteworthy for production purposes due to their wide availability and geographic distribution. They have been used by rural populations to treat common illnesses. The plants were collected and essential oils were extracted, before being plated in assays both with polysorbate 80 and without. Other assays were also created as controls. The antimicrobial activity was tested with bacteria, yeasts, and filamentous fungi, and a minimum inhibitory concentration (MIC), the minimum required concentration of essential oil to inhibit microbial growth, was determined. A combination of the essential oil and polysorbate 80 was also added to cosmetics and orange juice to determine preservative properties. Mutagenicity and toxicity were also evaluated, in chemical assays and in mice, respectively.
Researchers found that the essential oil was active in its antimicrobial properties against all microbes tested, and that the MIC decreased when polysorbate 80 was added. In cosmetics, the oil was only active in aqueous form and not when presented in cream products. It was, however, effective in orange juice, showing its activity in acidic media. The results in toxicity and mutagenicity classified the oil as non-toxic and non-mutagenic.
These results show that Lippia origanoides essential oil has promise to be an alternative to synthetic preservatives. An increase in concentration could lead to activity in cream form for cosmetics, though increases in concentration have been associated with allergenicity. The oil also produces a strong odour, which must be processed before use in products. Another issue is in its consistency. The chemical constituents of the oil can vary depending on the soil properties of where it is grown. This means that different antimicrobial properties may be shown depending on which plant is used. Thus, the oil must undergo chemical analysis before use as a preservative. Despite these problems, the essential oil has been shown to be an effective, broad, non-toxic and non-mutagenic preservative. With further research, Lippia origanoides essential oil could be used in food, cosmetic and pharmaceutical products as an alternative to synthetic preservatives.
Written By: Wesley Tin, BMSc