Antimicrobia activity of garlic (Allium sativum L.) and holy basil (Ocimum sanctum L.) essential oils applied by liquid vs. vapour phases

Abstract

Summary Antimicrobial activity of garlic (Allium sativum L.) and holy basil (Ocimum sanctum L.) essential oils (GEO and HBEO, respectively) was evaluated in liquid vs. vapour phases. Diallyl disulphide and diallyl trisulphide in GEO while eugenol, caryophyllene and methyl eugenol in HBEO were predominant active compounds. Individually, GEO was highly effective in the vapour phase, showing the greatest antimicrobial activity (P ≤ 0.05) against Bacillus cereus and Staphylococcus aureus with complete inhibition, followed by Salmonella typhimurium and Pseudomonas fluorescens, but had no effect on Escherichia coli, Lactobacillus plantarum or Listeria monocytogenes. The combined GEO:HBEO (a 1:1 ratio) at 30 μL demonstrated inhibitive activity against all bacteria tested with complete inhibition against B. cereus and S. aureus. Minimum bactericidal concentration (MBC) of the combined oil was <0.4% v/v, except for P. fluorescens requiring a higher MBC (1.5%, v/v). This study demonstrated potential of the combined GEO:HBEO to be used for food preservation applications.

Edible films containing carvacrol and cinnamaldehyde inactivate Escherichia coli O157:H7 on organic leafy greens in sealed plastic bags

“…As noted above (Goñi et al, ), Salmonella behaved very differently than did E. coli O157:H7, toward vaporized cinnamon and clove EOs. Torpol, Wiriyacharee, Sriwattana, Sangsuwan, and Prinyawiwatkul () found that Salmonella was significantly inhibited by garlic EO, both by vapor and disc diffusion contact methods, whereas E. coli O157:H7 was unaffected. Nedorostova, Kloucek, Kokoska, Stolcova, and Pulkrabek () showed that the responses of E. coli O157:H7 and Salmonella Enteritidis varied depending on the EO vapor tested.…”

Optimising chitosan–pectin hydrogel beads containing combined garlic and holy basil essential oils and their application as antimicrobial inhibitor

“…A previous study (Torpol et al ., ) showed that HBEO contained eugenol (49.87%) and caryophyllene (4.96%) as main components, however, DADS (31.67%), DATS (31.56%) and DATTS (13.48%) were the major fractions in GEO. Consequently, the combined GEO+HBEO (1:1 v/v) was potentially a strong antimicrobial inhibitor because HBEO contributed a large percentage of eugenol and caryophyllene as inhibitory agents, and DATTS was a key fraction of GEO.…”

“…After extraction at 25 °C for 30 min, SPME fibre with adsorbed volatile components was inserted into the injection port of a GC–MS instrument (model GC‐7890A, Hewlett‐Packard, Santa Clara, CA, USA) equipped with a DB‐5 capillary column (30 m, 0.25 mm I.D., 0.25 μm film thickness) and MS detector (MSD 5975C), and the volatiles identified and quantified according to the method of Torpol et al . ().…”

“…Combined GEO+HBEO (0.5 mL) or 2.20 g beads were added into vials, and an SPME fibre coated with 100 lm of polydimethylsiloxane was inserted into the headspace of the sample vials. After extraction at 25°C for 30 min, SPME fibre with adsorbed volatile components was inserted into the injection port of a GC-MS instrument (model GC-7890A, Hewlett-Packard, Santa Clara, CA, USA) equipped with a DB-5 capillary column (30 m, 0.25 mm I.D., 0.25 lm film thickness) and MS detector (MSD 5975C), and the volatiles identified and quantified according to the method of Torpol et al (2018).…”

“…While the single EOs display a certain degree of antimicrobial activity, the synergistic actions of mixed oil fractions are often exploited to improve the potency and antimicrobial activity spectrum of the individual oils (Nedorostova et al, 2009;Boukhatem et al, 2013). For instance, GEO alone inhibited Bacillus cereus, Clostridium perfringens, Pseudomonas fluorescens, Salmonella Typhimurium and Staphylococcus aureus but had no effect on Escherichia coli, Listeria monocytogenes, Lactobacillus plantarum, however, the 1:1 ratio of GEO (containing diallyl di-and trisulphides [DADS and DATS, respectively]) and HBEO (containing eugenol, methyl eugenol and caryophyllene) inhibited all the bacteria tested (Torpol et al, 2018).…”