Mohammad Mizanur Rahman

The effectiveness of lemon myrtle (LM) (Backhousia citriodora) essential oil (EO) was investigated to combat Penicillium digitatum by in vitro agar diffusion and vapour assay and in artificially infected oranges. The main constituent of LM EO was revealed as citral when analysed in gas chromatography–mass spectrometry. Pure citral was also included in the experiment for comparison. The in vitro fungal growth was significantly inhibited by LM EO at 1, 2, 3, 4 and 5 μL per disc while complete growth inhibition by both the pure citral and LM EO occurred at 4 and 5 μL per disc. Inoculated fruits treated by dipping in 1000 μL L⁻¹ LM EO solutions for 5, 10, 15, 30 and 120 s showed significantly lower fungal wounds compared to control. While longer dipping times led to some rind injuries, fruits with a 5 and 10 s dip were found free from any injury. The evaluation after dipping and storage confirmed that the fruits maintained the sensory attributes and were not compromised by the incorporation of the essential oil. The results of this study indicate that LM EO can be a promising alternative to synthetic fungicides for preserving the quality of citrus fruits during storage.

This study examined the efficacy of essential oil (EO) obtained from the Australian native plants, lemon myrtle (Backhousia citriodora) (LM) to inhibit Penicillium digitatum by in vitro agar diffusion and vapor assay, and in inoculated oranges. Gas chromatograph/mass spectrometry analysis revealed the main constituent of LM EO as citral. Pure citral was also included in the experiment for com-parison. LM EO at 1, 2, 3, 4 and 5 µL disc-1 in the in vitro tests significantly inhibited fungal growth compared to the non-treated control. Moreover, LM EO at 4 and 5 µL disc-1 in both the assays completely inhibited fungal growth similar to its main component of citral. Inoculated oranges dipped in 1000 μL L-1 LM EO solutions for 5, 10, 15 and 30 sec showed significantly lower fungal wounds compared to control. While higher dipping times generated slight rind injury, a 5 and 10 sec dip did not cause any injury to the fruit rind. The quality assessments and sensory evaluations also revealed that the addition of LM EO did not adversely affect the quality and taste of the oranges. These findings suggest LM EO as an alternative to synthetic fungicides to inhibit wastage in citrus during storage.

Limiting postharvest losses of fruit from fungal attack is a major priority. While synthetic chemical fungicides are efficacious, the development of chemical resistance and consumer concerns are driving reinvestigation of natural antimicrobial agents. This review emphasizes the control of postharvest decay in citrus fruits with the use of some most common essential oils (EO), the efficacy of EOs in combating fungal infection in both in vitro and in vivo models, and the mode of action of EOs along with the potency of photochemical by-products that have also been investigated as antifungal agents.

This study investigated the effects of four flavonoids on growth and flesh quality of grass carp (Ctenopharyngodon idellus). Five diets were designed with the supplementation of quercetin (QC), rutin (RT), baicalein (BC) and catechin (CC) in basal diet (control) and were fed to grass carp (59.7 ± 0.2 g) for 60 days. The fish fed QC and RT diets, rather than BC and CC diets, showed higher weight gain (+4.0%, +3.9%) and lower feed conversion ratio (−0.07, −0.06) than the control fish. The contents of total collagen, heat-soluble collagen, total free amino acids and flavour amino acids in flesh were significantly increased by the supplementation of QC and RT in diets. The SOD activity and the contents of C22:5, C22:6 and n-3 PUFA were significantly increased, and the malondialdehyde and protein carbonyl contents were significantly decreased in the QC, RT and CC groups. In the metabolomics profiling of muscle, 102 and 68 named differential metabolites were identified in the QC and RT groups, and these metabolites were found to be involved in the pathways of “lipid metabolism” and “amino acid metabolism.” In addition, the mRNA expressions of IGF-1, PI3K, AKT and FAS in flesh were significantly up-regulated in QC and RT groups. In summary, dietary QC and RT promoted the growth and flesh quality of grass carp which might be associated with IGF-1/TOR, Nrf2, TGF-β/Smad4 and PPAR signalling pathway.

The effect of UV-C irradiation on antifungal properties of orange essential oil (EO) against Penicillium digitatum in inoculated Navel oranges was examined. The UV-C irradiation of orange EO resulted in a 20% loss of the major constituent, limonene, and the generation of three hydroperoxide oxidation products, (2S,4R)-p-mentha-6,8-diene-2-hydroperoxide,(1S,4R)-p-mentha-2,8-diene-1-hydroperoxide, and (1R,4R)-p-mentha-2,8-diene-1-hydroperoxide. The P. digitatum growth in oranges dipped in non-irradiated orange EO at 1000–4000 µL L⁻¹ was not significantly different to control the fruit. Dipping in UV-C treated orange EO inhibited the growth of P. digitatum with 4000 µL L⁻¹ having the greatest effect. No phytotoxic injury to the rind was observed at any concentration. Citral, as a known antifungal chemical, was included for comparison. The non-irradiated citral (1000 µL L⁻¹) was more effective than irradiated orange EO, but elicited rind phytotoxicity. The irradiated citral was less effective in inhibiting P. digitatum growth with the loss of citral, but not hydroperoxide formation. These results suggest UV-C irradiated orange EO as a potential alternative to synthetic fungicides to inhibit P. digitatum decay. The source of orange EO could be waste flavedo generated by the orange juice processing industry.