Chemical composition, antioxidant and antimicrobial activity of essential oils from tangerine (Citrus reticulata L.), grapefruit (Citrus paradisi L.), lemon (Citrus lemon L.) and cinnamon (Cinnamomum zeylanicum Blume).

The phytochemical and biological properties of tangerine (Citrus reticulata L.), grapefruit (Citrus paradisi L.), lemon (Citrus lemon L.) and cinnamon (Cinnamomum zeylanicum Blume) essential oils were examined. The chemical composition of the essential oils determined using chromatography analysis revealed that D-limonene and cis-cinnamaldehyde were the main components. The antioxidant and antimicrobial activities of the essential oils have been studied by the DPPH radical-scavenging assay and the disc-diffusion method, respectively. All essential oils had antimicrobial activity against saprophytic (Bacillus subtilis, Penicillium chrysogenum, Fusarium moniliforme, Aspergillus niger, Aspergillus flavus, Saccharomyces cerevisiae) and pathogenic microorganisms (Escherichia coli, Salmonella abony, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans), with the highest inhibitory activity being observed in cinnamon oil, followed by grapefruit zest oil, tangerine zest oil and lemon zest oil; the MIC ranging from 6 to 60 ppm. In addition, they exhibited high antioxidant activity with the highest antioxidant activity being determined for the grapefruit zest essential oil, followed by the lemon zest essential oil, the tangerine zest essential oil and the cinnamon essential oil. The demonstrated promising results for the antioxidant and antimicrobial activity of the studied essential oils would give reason for their inclusion in the development of bio-preservation strategies for food emulsion preservation.

Production of probiotic wort-based beverages with grapefruit (Citrus paradisi L.) or tangerine (Citrus reticulata L.) zest essential oil addition.

BACKGROUND: In recent years, increasing health awareness in consumers has motivated breweries to expand their beverage ranges with products with increased biological value. The aim of the present research was to develop probiotic wort-based beverages with grapefruit or tangerine zest essential oil addition. METHODS: Wort was produced with 60% Pilsen malt, 20% Vienna malt and 20% Caramel Munich ІІ malt with and without the addition of 0.05% (v/v) grapefruit or tangerine essential oils. It was inoculated with the probiotic yeast strain Saccharomyces cerevisiae var. boulardii Y1. Fermentations were carried out at a constant temperature of 10°C for 5 days. The dynamics of the extract, the alcohol content and the concentration of viable cells were monitored daily. The total phenolic content, phenolic acid and flavonoid phenolic compounds were determined because of their antioxidant activity. The antioxidant activity was determined by radical scavenging assay (DPPH) and ferric reducing antioxidant power (FRAP). A descriptive organoleptic evaluation of the final beverages was performed. RESULTS: The essential oils inhibited yeast growth to some extent at the beginning of the fermentation, even at a concentration of 0.05% (v/v), which resulted in lower alcohol content in the beverages with essential oil addition. Nevertheless, at the end of fermentation the concentration of viable cells was almost equal in all the beverages. Tangerine essential oil addition led to the highest content of phenolics, of which phenolic acids predominated. Therefore, the highest antioxidant activity of the beverage with tangerine essential oil can be ascribed to phenolic acids. The results of the sensorial evaluation also showed that the panel had preference towards the beverage with tangerine essential oil. CONCLUSIONS: The combination of essential oil and the probiotic yeast strain resulted in beverages with higher biological value than the beverages produced with the probiotic strain alone. The results obtained will be used for optimisation of process variables in the production of pilot-scale wort-based probiotic beverages with essential oil addition.

Bio-preservation of chocolate mousse with free and immobilized cells of Lactobacillus plantarum D2 and lemon (Citrus lemon L.) or grapefruit (Citrus paradisi L.) zest essential oils.

BACKGROUND: The bio-preservation of food products using various natural ingredients and metabolites from various types of beneficial microorganisms released during targeted fermentation is a method that simultaneously has a preservative effect on the food product and provides a model of its composition in order to ensure its functional and health properties. This double effect can be achieved by incorporating ingredients with proven preservative and functional effects into the food product, such as essential oils from various plant species and probiotic bacteria. The aim of the present research was to study the synergistic effect of selected probiotic lactic acid bacteria (LAB) and essential oils with high antimicrobial activity against pathogenic and spoilage microorganisms for the bio-preservation of chocolate mousse food emulsion. METHODS: The susceptibility of the selected probiotic strain Lactobacillus plantarum D2 to different concentrations of the selected lemon or grapefruit essential oil was examined using the disc-diffusion method. Nine chocolate mousse variants were prepared with the inclusion of free or immobilized cells of the probiotic strain L. plantarum D2 and/or lemon or grapefruit zest essential oils. The chocolate mousse variants were stored for 20 days in refrigerated conditions, and changes in the concentration of viable lactobacilli cells, the pH and the microbiological purity were monitored in accordance with standard requirements by taking samples on the 0th, 5th, 10th, 15th, and 20th days of storage. An organoleptic evaluation of the chocolate variants was performed on the 0th day. RESULTS: Concentrations of up to 1% lemon or grapefruit essential oil did not affect the growth of the probiotic strain L. plantarum D2, which revealed opportunities for their joint application for the bio-preservation of food emulsions. The obtained chocolate mousse variants were characterized by preserved organoleptic characteristics and microbiological safety. Free or immobilized probiotic L. plantarum D2 cells applied alone or in combination with lemon or grapefruit essential oils provided bio-preservation of the food emulsions, maintaining a high concentration of viable cells (106-107 cfu/g) during storage under refrigerated conditions for 20 days. CONCLUSIONS: The combined application of free or immobilized probiotic LAB and lemon or grapefruit essential oils resulted in better bio-preservation results than in the use of probiotic LAB or essential oils alone, thus suggesting a synergistic effect between the two bio-preservative agents. Moreover, the obtained chocolate mousse emulsions can be classified as functional foods and the chocolate mousse food matrix can successfully be used as a vehicle for delivery of probiotic LAB to a wide range of food consumers. The obtained results and the developed successful bio-preservation strategy for the production of chocolate mousse food emulsions would provide grounds for the future selection of other probiotic lactobacilli strains, essential oils and synergistic combinations of them for the development of successful bio-preservation strategies for other types of food and beverage products.

Biological preservation of mayonnaise with Lactobacillus plantarum LBRZ12, dill, and basil essential oils.

In this study, different variants of egg-free mayonnaise containing free and immobilized Lactobacillus plantarum LBRZ12 cells and essential oils taken from basil and dill were prepared. The composition and antimicrobial properties of essential oils were investigated. The main constituents of basil oil were methyl chavicol (36.81%), methyl eugenol (20.40%), ß-linanool (14.35%), eugenol (10.55%), and L(-)-carvone (39.05%), whereas dill oil contained mostly d-limonene (21.11%) and α-phellandrene (22.68%). The essential oils exhibited strong antimicrobial activity against all test-microorganisms. The mayonnaise variants were kept refrigerated for 40 days and changes in pH, concentration of viable cells of lactobacilli, microbiological, and organoleptic characteristics were monitored. The pH decreased from 6.5 to 4.5 over the period of storage. The number of undesired microflora in mayonnaise preserved with lactobacilli and essential oils decreased significantly (0 after the 20th day) indicating their effectiveness as biological preservatives. The mayonnaise variants demonstrated pleasant organoleptic characteristics, thus meet customers' requirements.

Chemical composition, antioxidant activity and antimicrobial activity of essential oil from Citrus aurantium L zest against some pathogenic microorganisms.

This study aims to investigate the chemical composition, antioxidant, and antimicrobial activity of Citrus aurantium L zest essential oil. The identification of the chemical compounds was done using chromatography analysis. The antioxidant activity was studied by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Results showed that the main components of the essential oil were limonene (85.22%), ß-myrcene (4.3%), and α-pinene (1.29%). Regarding the DPPH radical scavenging ability, the zest essential oil showed higher activity than limonene. The antimicrobial activity of the essential oil against pathogenic [Staphylococcus aureus NBIMCC 3703, Salmonella sp. (clinical isolate), Pseudomonas aeruginosa NBIMCC 1390, Bacillus subtilis NBIMCC 1208, Escherichia coli NBIMCC 3702] microorganisms by disc-diffusion method was examined. Gram-positive bacteria were more sensitive to the oil (inhibition zones being between 9 and 12.5 mm) and the minimum inhibitory concentration was more than 600 ppm; Gram-negative bacteria were less sensitive. The obtained essential oil displayed promising results for its application as a biopreservative agent.