Science
Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/1
Browse
7 results
Search Results
Item Inhibition of aspergillus flavus link and aflatoxin formation hy essential oils of cinnamomum xeylanicum (L) and cymbopogon nardus rendle(Postgraduate Institute of Agriculture, University of Peradeniya: Peradeniya, 2002) Jayaratna, K.H.T.; Pranagama, P.A.; Abeywickrama, K.P.; Nugaliyadde, L.The essential oils of Cinnamomum zeylanicum (L.) leaf and Cvmbopoeon nardus Rendle were tested for their fungistatic, fungicidal and qflatoxin suppressing efficacy against an isolate of Aspergillus flavus Link, isolated from rice. The mycelial growth and the aflatoxin formation in SMKY semi synthetic liquid medium in the presence of different concentrations of two test oils were monitored. At concentrations varying from 100 to 500 ppm of the essential oil of C. zeylanicum. the mycelial dry weight decreased from 0.49 to 0.01 g/50 ml. The percentage inhibition of the mycelial growth of A. flavus increased from 50 to 95 when treated with 1000 to 1800 ppm of C. nardus oil. The minimum lethal concentrations (MLCs) for the essential oils of C. zeylanicum leaf and C. nardus were 1000 and 4000 ppm, respectively. Aflutoxins were not present in the medium at or above the concentrations of400 and 600 ppm C zeylanicum leaf and C nardus oils, respectivelyItem Deterrent effects of some Sri Lankan essential oils on oviposition and progeny production of the cowpea bruchid, Callosobruchus maculatus (F.)(Coleoptera; Bruchidae)(2003) Paranagama, P.; Adhikari, C.; Abeywickrama, K.P.; Bandara, P.Essential oils extracted from five plant materials were tested on oviposition and progeny production of F1 adult of cowpea bruchid, Callosobruchus maculatus on cowpea seeds. All oils tested showed a significant inhibition of oviposition and F1 adult emergence compared to the control during no-choice tests. Cymbopogon citratus and C. nardus showed higher effect on oviposition and F1 adult emergence than the essential oils of Alpinia calcarata, Cinnamomum zeylanicum and Murraya koinigii. In the choice test, the percentage ovipositions in all oils treated samples (except 10 mg of M. koinigii) were significantly lower than that of the control and ethanol treated samples. The percentage eggs deposited decreased with increasing doses of the oils ranging from 10 to 160 mg. The percentage of eggs laid was zero in samples treated with 40 mg of C. nardus or A. calcarata, 80 mg of C. citratus and 160 mg of C. zeylanicum. The essential oils of M. koinigii showed the lowest effect on oviposition when compared to other four essential oils.Item Cymbopogon citratus (lemongrass) and citral a+ b spray treatments alone or in combination with sodium bicarbonate in controlling crown rot in Embul banana (Musa acuminata AAB)(2004) Abeywickrama, K.P.; Kularathna, L.; Sarananda, K.; Abeygunawardena, D.The mounting pressure against synthetic fungicidal dips and sprays, restrict their use in controlling crown rot, a major post-harvest disease in banana. Generally regarded as safe (GRAS) compounds have a great potential to be used as alternatives to fungicides. Identification of chemical constituents of Cymbopogon citratus oil revealed the presence of citral as the main component. Cymbopogon citratus and citral with sodium bicarbonate (SBC) was fungicidal against the 3 banana fungal pathogens at 0.10-0.20 % v/v and 0.07-0.08 % v/v respectively. Embul banana sprayed with C. citratus alone or in combination with SBC after induced ripening, indicated a crown rot severity of 25 - 5 0% whereas, citral treatment resulted in a slightly lower disease severity. The physico-chemical parameters tested were not affected by the treatments. Oil/citral, SBC treated bananas and control were ranked good to excellent with respect to odour, flavour, taste and overall acceptability. The low disease severity of crown rot due to spray treatment of citral and SBC highlights the importance in adapting this simple, alternate treatment strategy for quality maintenance.Item Aflatoxigenic Aspergillus flavus and aflatoxin formation in selected spices during storage(2009) Rajasinghe, M.; Abeywickrama, K.P.; Jayasekera, R.Proliferation of aflatoxigenic fungi and accumulation of aflatoxins take place during storage of spices at various environmental conditions. The objective of this research was to identify the aflatoxigenic fungal species and their aflatoxin forming potential in selected spices during storage in the laboratory and refrigerator. Dilution series of spice samples namely chilli (Capsicum annum) powder, curry powder, turmeric (Curcurma longa) powder and pepper (Piper nigrum) powder (purchased from two producers) were prepared separately and the frequency of occurrence of aflatoxigenic and other fungi were assessed after plating each on Potato Dextrose Agar and incubating at ambient temperature. Aflatoxin formation of A. flavus was confirmed by growing a pure culture on a SMKY medium and identifying toxins on thin layer chromatographic plates. The presence of aflatoxins in spice samples stored at 30 ± 20C and 40C was also confirmed. Long storage of spices leads to aflatoxin production irrespective of storage temperature hence, it is advisable to consume spices such as chilli powerder, tumeric etc. within a relatively short period to avoid build up of aflatoxins.Item Quality assessment minimally processed immature jackfruit (Artocarpus heterophyllus, Lam.) as affected by pretreatments(Association of Food Scientists & Technologists, India, 2015) Ekanayaka, H.; Abeywickrama, K.P.; Jayakody, R.; Herath, I.Abstract Degree of browning, firmness, sensory properties and microbiological quality of minimally processed immature jakfruit were investigated on initial and seventh day after stor- age at 5–7 °C. Samples were pretreated with 0.5 % and 1 % sodium metabisulphite, 1.5 % citric acid+1.5 % ascorbic acid, 3 % citric acid, 3 % ascorbic acid and packed in polystyrene packages and over wrapped with polyvinylchloride (PVC) stretch film before storage. When degree of browning in rela- tion to absorbance was assessed, immature jakfruit pretreated with 1.5 % citric acid+1.5 % ascorbic acid showed the lowest absorbance at 420 nm among all pretreated samples indicating low browning in samples. At 450 nm, minimally processed immature jackfruit samples pretreated with 1.5 % citric acid+ 1.5 % ascorbic acid showed the highest reflectance (indicating lowest absorbance) compared to other treatments. Variations in firmness were observed after treatment. Microbial counts were within safe-to-consume limits while coliforms were not detected in any of the samples. Erwinia aphidicola and Bacillus subtilis were identified from minimally processed immature jakfruit samples using molecular tools. 1.5 % citric acid+1.5 % ascorbic acid, 1 % sodium metabisulphite and 3 % citric acid were relatively more successful in retaining acceptable sensory quality of jakfruit even after 7 days of storage. Above pretreatments could be recommended during minimal processing of immature jakfruit meant for local sale in supermarkets where cold storage is available.Item Polyphenol oxidase inhibitory activity of essential oils of Cymbopogon nardus and Cymbopogon citratus(Journal of Tropical Medicinal plants, 2003) Ranasinghe, L.S.; Jayawardena, B.M.; Abeywickrama, K.P.Polyphenol oxidase (tyrosinase) (EC 1.14 18.1) is responsible for the hyperpigmentation in humans, insect molting process and browning reactions of plants. There is interest to develop methods to control polyphenol oxidase reaction. Essential oils of lemon grass, Cymbopogon citratus (D.C.) Stapf. and citronella, Cymbopogan nardus Rendle were found to inhibit the activity of polyphenol oxidase. Cinnamic acid inhibited the oxidation with an ID value of 0.351 (mg/ml). Citronella and lemongrass oils could be used as naturally occurring inhibitors for Polyphenol oxidase.Item The efficacy of essential oil of Alpinia calcarata (Rosc.) and its major constituent, 1,8-cineole, as protectants of cowpea against Callosobruchusmanculatus(F.) (Coloeptera; Bruchidae)(Canadian Journal of Plant Science, 2006) Abeywickrama, K.P.; Adhikari, A.A.C.K.; Paranagama, P.A.; Gamage, C.S.P.