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In the present research, the antifungal and antioxidant activities of Mentha piperita essential oil (MPEO) were investigated, and its potential as a natural food preservative in Orangina juices was evaluated. The major component was menthol (54.47%). The percentage inhibitions of MPEO were dose dependent with IC50 values of 2.53±1.77 mg/mL in DPPH test and 8.24±1.16 mg/mL in metal complexing ability. The microbial inhibition of MPEO was assessed against different food spoiling strains. The MPEO strongly inhibited the growth of Rhodotorula sp. and Saccharomyces cerevisiae with a diameter of the inhibitory zone (DIZ) ranging from 17-85 mm at the lower dose (20 µL), and from 35-85 mm at the higher quantity (60 µL). The minimum inhibitory concentration varied from 0.0078 to 0.5% (v/v) for yeasts. In addition, the anti-yeast effectiveness of MPEO alone and in association with moderate heat treatment was investigated in Orangina juices. The juices treated with association of MPEO at different doses (1, 2 and 6 µL/mL) and medium heat treatment (80 °C for 2 min) improved the reduction of Saccharomyces cerevisiae viability cells. Present data confirmed the superior performance of integrated thermal treatment over individual use of peppermint oil for Orangina juices preservation. [ABSTRACT FROM AUTHOR]

Two different extraction methods were used for a comparative study of Algerian Myrtle leaf essential oils: solvent-free-microwave-extraction (SFME) and conventional hydrodistillation (HD). Essential oils analyzed by GC and GC-MS presented 51 components constituting 97.71 and 97.39% of the total oils, respectively. Solvent-Free-Microwave-Extract Essential oils SFME-EO were richer in oxygenated compounds. Their major compounds were 1,8-cineole, followed by a-pinene as against a-pinene, followed by 1,8-cineole for HD. Their antimicrobial activity was investigated on 12 microorganisms. The antioxidant activities were studied with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method. Generally, both essential oils showed high antimicrobial and weak antioxidant activities. Microstructure analyses were also undertaken on the solid residue of myrtle leaves by Scanning Electronic Microscopy (SEM); it showed that the SFME-cellular structure undergoes significant modifications compared to the conventional HD residual solid. Comparison between hydrodistillation and SFME presented numerous distinctions. Several advantages with SFME were observed: faster kinetics and higher efficiency with similar yields: 0.32% dry basis, in 30 min as against 180 min for HD. [ABSTRACT FROM AUTHOR]