Chemical composition, in vitro anti-yeast activity and fruit juice preservation potential of lemon grass oil

The anti-yeast activity of lemon grass oil was evaluated against several food spoiling yeasts (Saccharomyces cerevisiae, Zygosaccharomyces bailii, Aureobasidium pullulans, Candida diversa, Pichia fermentans, Pichia kluyveri, Pichia anomala and Hansenula polymorpha) through disc diffusion and microbroth dilution method. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) varied from 0.28 to 1.3 mg/ml and 0.56 to 4.5 mg/ml, respectively, where highest MIC (2.25 mg/ml) was shown by A. pullulans and lowest MIC (0.28 mg/ml) was shown by C. diversa and P. anomala. Kill time assay was conducted for selected three yeast strains where S. cerevisiae showed highest reduction (3 log cfu) in viability within 24 h exposure of lemon grass oil at MFC level. Further, the anti-yeast efficacy of lemon grass oil alone and in combination with thermal treatment was evaluated in real food system i.e. mixed fruit juices. Chemical composition analysis of lemon grass oil by gas chromatography–mass spectrometry (GC–MS) revealed that the dominant compounds were geranial (40.5%), neral (30.7%), geranyl acetate (5.1%), caryophyllene (2.5%). Present results established the superior performance of integrated (thermal–lemon grass oil) treatment over the individual exposure (lemon grass oil or thermal treatment alone) for fruit juice preservation.