Efficacy of Ocimum tenuiflorum essential oil as grain protectant against coleopteran beetle, infesting stored pulses.

In the present investigation, essential oil (EO) of Ocimum tenuiflorum and its principal constituent (eugenol) was evaluated for its toxicity and mode of action against Callosobruchus maculatus. Furthermore, fumigant toxicity and germination studies on the application of O. tenuiflorum EO and eugenol against C. maculatus on different pulses was also studied. Fumigant activity studies revealed that EO toxicity was significantly (p < 0.05) influenced by concentration and exposure time. In fumigant toxicity assay without food, O. tenuiflorum EO and eugenol showed LC50 value of 278.6 and 256.5 µL/L air, respectively, at one hour exposure. Further, O. tenuiflorum EO displayed fumigant toxicity via inhibiting acetylcholinesterase activity. Pulses treated with O. tenuiflorum EO showed 70% of C. maculatus mortality at 250 µL/L air concentration after 24 h. Furthermore, these treatments didn't affect the seed viability of the pulses tested. Hence, the application of O. tenuiflorum EO has potential scope as a botanical insecticide.

In-vitro evaluation of antimicrobial and insect repellent potential of supercritical-carbon dioxide (SCF-CO2) extracts of selected botanicals against stored product pests and foodborne pathogens.

In the present study, the antimicrobial and the insect repellent activity of 16 botanical extracts obtained by supercritical CO2 (SCF) extraction were evaluated. The present investigation was conducted as there is a necessity for exploration of natural botanical extracts that target both stored product insects and microbes. The antimicrobial activity was studied by disc diffusion and broth microdilution methods against ten microbial species, including Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis and Listeria monocytogenes), Gram-negative bacteria (Escherichia coli and Salmonella enterica), and fungi (Aspergillus flavus, Aspergillus paraciticus, Aspergillus ochraceous, Aspergillus niger and Penicillium verrucosum). Repellency assay was carried out by area preference method against three coleopteran insects (Tribolium castaneum, Rhyzopertha dominica and Sitophilus oryzae). Among all the extracts, thyme and ajwain were effective against all the tested bacteria with a minimum inhibition concentration (MIC) of 256-1024 µg/mL. Hop extract resulted in better antibacterial activity against all the tested Gram-positive bacteria with a MIC of 32-64 µg/mL. Oregano, thyme and ajwain extracts showed broad-spectrum antifungal activity against all the tested fungi with MIC of 128-1024 µg/mL. Most of the extracts exhibited class V (80.1-100%) repellency against T. castaneum. Extracts of hop, ajwain and thyme were found to have strong repellency against T. castaneum and R. dominica. Therefore, SCF extracts of ajwain and thyme can be explored further for the application of bio-extracts as a growth limiting factors in a microcosm where such consortia thrive.

Potential of pyrethroid-synergised pyrethrum on stored product insects and implications for use as prophylactic sprays.

The study was conducted to evaluate the synergistic effects of 2% pyrethrum extract with synthetic pyrethroids on the mortality of stored product insects. Contact toxicity was performed at variable concentrations observing mortality at 12, 24 and 48 h durations. The results of the present study indicated that, pyrethrum + deltamethrin combination (25:1 ratio) was effective on the adults of Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst). On the other hand, pyrethrum + cypermethrin combination proved effective against Sitophilus oryzae (L.). The efficacy of the tested combination showed reasonable increase in mortality response in treated insects over increasing exposures. At 48 h, 450 ppm pyrethrum + deltamethrin combination induced 25, 90 and 97% mortalities in S. oryzae, T. castaneum and R. dominica adults; while, pyrethrum-cypermethrin combination recorded 75, 45 and 75% mortalities respectively. On the other hand, it was observed that, among the pyrethrum alone treatments i.e. at 300, 450 and 600 ppm concentrations, maximum mortality (62.5%) was observed in S. oryzae exposed to 600 ppm pyrethrum for 48 h. The effective LC50 concentrations for pyrethrum (600 ppm) + deltamethrin combination was estimated to be as 0.1987 and 0.7039 µl/cm2 for R. dominica and T. castaneum adults respectively. Contrastingly, for treatments with S. oryzae, a LC50 value of 0.8673 µl/cm2 was recorded for pyrethrum (600 ppm) + cypermethrin mixture. This investigation strengthens the fact that pyrethrum along with pyrethroids is effective against storage insect pests which can be promisingly a safer insecticidal combination.

Development and validation of headspace Solid-Phase microextraction coupled with gas chromatography (HS-SPME-GC) method for the analysis of zingiber zerumbet L.

Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography (GC-FID) was explored to determine the fingerprinting characteristic of Zingiber zerumbet L. volatiles to differentiate between different ginger species. The effect of different fibers [polydimethylsiloxane (PDMS, 7 µm), polyacrylate (PA, 85 µm)], different temperature and time on the HS-SPME-GC was investigated by using response surface methodology coupled with full factorial experimental design. The area percentage of the major sesquiterpenes (Zerumbone and α-humulene) were 56.3 ± 4.7% and 47.5 ± 27.2% with PA fiber, respectively at optimum condition of 70 °C and 30 min. Validation of the developed HS-SPME-GC method with limits of detection and quantification for zerumbone was 0.09 and 0.28 µg/g, respectively, demonstrating the suitable sensitivity of HS-SPME-GC method for the quantification of sesquiterpenes. Therefore, the simplicity of HS-SPME-GC makes it a convenient tool for qualitative and quantitative comparison of different ginger species targeting at the marker sesquiterpene molecule, zerumbone.

Efficacy of blue LED in microbial inactivation: Effect of photosensitization and process parameters.

Efficacy of blue (462 ±â€¯3 nm) Light emitting diode (LED) illumination to inactivate the foodborne pathogens like Escherichia coli and Staphylococcus aureus in the presence of exogenous photosensitizer (curcumin) was studied in vitro. The effect of temperature, concentration of photosensitizer and incubation time with photosensitizer for microbial inactivation was investigated and sublethal injury of cells was determined. Mechanism of inactivation by the combination of photosensitizer and blue light was also examined. A maximum reduction of 5.94 ±â€¯0.22 and 5.91 ±â€¯0.20 log CFU/ml was obtained for E. coli and S. aureus, respectively, when treated with photosensitizer (20 µM) at 13 J/cm2 of blue light. There was no significant change in the inactivation of these pathogens both at 9 °C and 27 °C in the presence of photosensitizer. Even, the incubation with the photosensitizer didn't show any significant difference on the inactivation of these food-borne pathogens. Sublethal injury (>90% injury) was also observed for the cells treated with photosensitizer and blue light simultaneously. Confocal laser scanning microscopy analysis revealed that membrane integrity was disturbed due to photodynamic activity of curcumin in both the bacteria. Further, both cells produced intracellular reactive oxygen species by the action of photosensitizer and blue light. Scanning electron microscopy of E. coli and S. aureus cells treated with photosensitizer and blue light showed morphological changes in the cell wall compared to untreated group. The study indicated that photodynamic inactivation of foodborne pathogens using LED-based photosensitization can be explored as a potential technique for food safety.

Sono-photodynamic inactivation of Escherichia coli and Staphylococcus aureus in orange juice.

Efficiency of blue (462 ±â€¯3 nm) light emitting diode (LED) illumination to inactivate Escherichia coli and Staphylococcus aureus in the presence of exogenous photosensitizer (curcumin) was studied in freshly squeezed orange juice. Further, the combinational effect of ultrasound (US), photosensitizer (PS) and blue light (BL) on inactivation of microbes was evaluated. The effect of process parameters such as concentration of PS, US and volume of the juice on E. coli and S. aureus inactivation was also investigated. The US alone and PS + BL treatments resulted in 3.02 ±â€¯0.52 and 1.06 ±â€¯0.13 log reduction of E. coli; 0.18 ±â€¯0.14 and 2.34 ±â€¯0.13 log reduction of S. aureus, respectively. The combination of PS + US + BL treatment at optimized conditions resulted in 2.35 ±â€¯0.16 log reduction of S. aureus. An additive effect on the inactivation of E. coli (4.26 ±â€¯0.32 log reduction) was observed with PS + US + BL combination treatment. The US treatment showed significant change in cloud value, colour and browning index of orange juice. The combinational non-thermal processes (PS + BL and PS + US + BL) did not have any significant effect on total phenolic content, total flavonoid content, and hesperidin content of the orange juice. However, these processes affected ascorbic acid content and antioxidant activity negatively. Thus, this study indicated that photodynamic inactivation of E. coli and S. aureus using LED-based photosensitization in fruit juices could be a potential method for microbial inactivation. Nevertheless, the effect on quality parameters needs to be considered while optimizing the process.