Abstract
In the organic food industry, no chemical additives can be used to prevent microbial spoilage. As a consequence, the essential oils (EOs) obtained from organic aromatic herbs and spices are gaining interest for their potential as preservatives. The organic Thymus zygis, Thymus mastichina, Thymus capitatus and Thymus vulgaris EOs, which are common in Spain and widely used in the meat industry, could be used as antibacterial agents in food preservation. The aims of this study were to determine (i) the antibacterial activity using, as culture medium, extracts from meat homogenates (minced beef, cooked ham or dry-cured sausage); and (ii) the antioxidant properties of organic EOs obtained from T. zygis, T. mastichina, T. capitatus and T. vulgaris. The antioxidant activity was determined using different methodologies, such as Ferrous ion-chelating ability assay, Ferric reducing antioxidant power, ABTS radical cation (ABTS•+) scavenging activity assay and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method; while the antibacterial activity was determined against 10 bacteria using the agar diffusion method in different meat model media. All EOs analyzed, at all concentrations, showed antioxidant activity. T. capitatus and T. zygis EOs were the most active. The IC50 values, for DPPH, ABTS and FIC assays were 0.60, 1.41 and 4.44 mg/mL, respectively, for T. capitatus whilst for T. zygis were 0.90, 2.07 and 4.95 mg/mL, respectively. Regarding antibacterial activity, T. zygis and T. capitatus EOs, in all culture media, had the highest inhibition halos against all tested bacteria. In general terms, the antibacterial activity of all EOs assayed was higher in the medium made with minced beef than with the medium elaborated with cooked ham or dry-cured sausage.
Highlights
Greater understanding of the relationship between diet, specific food ingredients and health is leading to new insights into the effect of food components on physiological function and health.This awareness has moved consumers to become more health-conscious, driving a trend towards “green”, healthy and nutritious foods with additional health-promoting functions
The antioxidant activity of essential oils (EOs) obtained from T. zygis, T. mastichina, T. capitatus and T. vulgaris was determined using four different methodologies (DPPH and ABTS+ scavenging activity, reducing power and chelating activity), due to the fact that a single method will provide basic information about antioxidant properties, but a combination of methods will describe the antioxidant properties of the sample in more detail [18]
T. capitatus EO showed the strongest (p < 0.05) radical scavenging effect, with an IC50 value of 0.60 mg/mL followed by T. zygis EO, which had an IC50 value of 0.90 mg/mL
Summary
Greater understanding of the relationship between diet, specific food ingredients and health is leading to new insights into the effect of food components on physiological function and health This awareness has moved consumers to become more health-conscious, driving a trend towards “green”, healthy and nutritious foods with additional health-promoting functions. Aiming at the reduction of the use of chemical additives in the food industry, there has been growing interest recently in the use of natural food additives with antimicrobial and antioxidant properties that do not have any negative effects on human health [2] In this way, natural antioxidants extracted from plants can be used as alternatives to synthetic preservatives due to their equivalent or greater effect on the inhibition of lipid oxidation and bacterial growth [3]
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