International Research Symposium on Pure and Applied Sciences (IRSPAS)
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Item Developing a scale to assess the Spiralling Whitefly, Aleurodicus disperses Russel (Hemiptera: Aleyrodidae), infestation on cassava (Manihot esculenta)(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Gunawardana, D. U. M.; Warnasooriya, P. G. A. S.; Hemachandra, K. S.Spiralling whitefly, Aleurodicus dispersus Russel (Aleyrodidae) is a highly polyphagous quarantine pest, spread in tropical and subtropical region of the world. As direct feeders of cell sap whiteflies affect adversely on growth and act as vectors of viruses and spread plant diseases, of many agricultural and non-agricultural plants. This pest can be managed by the means of biological control with the use of coccinellid predators. In this process, it is necessary to make samples and assess the whitefly infestations in relation to many laboratory and field studies. In order to facilitate the assessment of whitefly populations, a study was conducted to develop a scale to measure the whitefly infestation in cassava. Whitefly infected cassava leaves were collected from cassava fields in Dholuwa-Kandy for one cropping season. Leaflets of collected leaves were separated (leaflet length 14.29 ± 0.43 cm, width 3.53 ± 0.21 cm and leaf area 57.86 ± 6.34 cm2 ) (n= 80). Each leaflet was examined separately under the binocular light microscope (10x4) and each growth stages (eggs, instar 1, instar 2, instar 3 and instar 4) of the whitefly were counted based on the four whitefly infestation levels (25%, 50%, 75% and 100%). The variation of eggs appears to have a more or less linear relationship with the area of infestation, but not the other growth stages. When total number of eggs is considered, a significant linear relationship (r2 = 87.1%, F (1, 78) = 524 p < 0.001) with infestation level was found which can be expressed as y =2.58 x +8.33. When total number of instars is considered, a significant linear relationship (r2 = 95.1%, F (1, 78) = 1521 p < 0.001) with infestation level was found which can be expressed as y =3.332 x +2.275. Eggs represented 80%, out of the total number of counted individuals. Significant relationships were observed between the area of infestation and instar 1, instar 2 and instar 3 but not with instar 4. Having considered these relationships, number of whitefly stages or the egg numbers can be predicted by examining the area of the infestation of the leaf, in this case cassava. There is a possibility, this pattern may be true for other crops but exact relationship is needed to be established, with a separate studyItem Preliminary study on starch extraction ratio and nutritional composition of two cassava cultivars(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Weerasinghe, R. K. L.; Wickramasinghe, I.; Somendrika, M. A. D.Cassava (Manihot esculanta) is one of the most important food crop among tropical countries. Cassava has higher carbohydrate content and its tapioca starch and modified tapioca starch is highly used as an ingredient of many food products. The objective of this preliminary study was to compare the starch yields and analyze the moisture, fat and protein contents of the extracted starch of two cassava cultivars (Kirikawadi and Muthukawadi variety). Cassava starch was extracted using good quality mature cassava roots. They were cleaned to remove mud, peeled, washed and grated. Those grated roots were milled with tap water mixing in 1:4 ratio by using laboratory scale blender at low speed and filtered through a muslin cloth. Residue was repeatedly milled and filtered again. The suspension was kept to sediment the starch for overnight. The supernatant was decanted and the settled residue was collected into a drying tray and was dried at 600C for 5 hr, dried sample was ground using laboratory blender, sieved through a 300 µm sieve, packed in airtight pouch, sealed in airtight container and stored in cold room (<50C). Cassava starch yield was calculated. Moisture content, fat content and protein contents were analyzed by AOAC (2012) methods. The average extraction ratio of Kirikawadi variety and Muthukawadi variety were 0.13 and 0.11. The average starch yield of Cassava Kirikawadi and Muthukawadi varieties were 12.8% and 11.05%. The flesh of the roots of Kirikawadi and Muthukawadi varieties contained average moisture content of 51.77% and 53.08% respectively. The average range of moisture content of starch of Kirikawadi variety ranged from 16.08% to 16.97% and Muthukawadi variety ranged from 6.99% to 8.43%. The crude fat content of starch of Kirikawadi variety ranged from 0.31% to 0.36% and Muthukawadi variety ranged from 2.14% to 3.29%. The average crude protein content of starch of Kirikawadi variety ranged between; from 2.37% to 3.35% and it ranged from 2.46% to 2.53% in Muthukawadi variety starch. There was a significant difference (p<0.05) between the average moisture content of starch extracted from Kirikawadi and Muthukawadi. Furthemore, there was a significant difference (p<0.05) between the average fat content and there was no significant difference (p>0.05) between average protein content of starch extracted from Kirikawadi and Muthukawadi.Item Microbial enumeration assay of fermented products of cassava variety MU51(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Perera, T. W. N. K.; Amarakoon, R.; Edirisinghe, E. A. A. D.This study was carried out to investigate the effects of solid state fermentation of cassava variety MU51, on the qualitative properties and total viable microbial counts, of the fermented cassava products, developed by changing the fermentation lengths as two days and three days. The steps involved in the product development are peeling, washing, grating cassava roots into a mash, collecting the mash into sacks, dewatering and fermenting the mash under natural environmental conditions. The fermented, wet cakes obtained are further de-watered by oven-drying process to make fermented, dry products. These fermented dry cassava products appear cream-white in color and soft granular or powdered form in texture. Both products have a fermented smell and the pH value is 5. Microbial enumeration assay is carried out for the raw cassava, fermented wet cakes and fermented dry products, using plate count technique. Particular attention is given on mesophilic, aerobic and facultative anaerobic microorganisms. The bacterial count of raw cassava is (1.8-2.2) x10³ colony forming units per gram. For two days fermented wet cake, the bacterial count is (2.9-3.4) x10⁴ colony forming units per gram and for three days fermented wet cake, it is (2.8-3.3) x10⁴ colony forming units per gram. During fermentation, the bacterial count increases. Increase of acidity during fermentation and depletion of substrates could contribute to a slight decrease in the viable bacterial population, during later stage of fermentation. The fungal count of raw cassava is (6.3-8.6) x10² colony forming units per gram. Fungal count of two days fermented wet cake is 8.5x10² - 1.1x10³ colony forming units per gram and three days fermented wet cake is (1.1-1.3) x10³ colony forming units per gram. During fermentation, the fungal count increases as fungi are favored by the acidification of pulp and are benefited from the metabolites sourced from the growth of other microorganisms. Bacterial count of two days fermented dry product is (2.7-3.2) x10⁴ colony forming units per gram and three days fermented dry product is (2.6-3.0) x10⁴ colony forming units per gram. Fungal count of two days fermented dry product is (7.4-8.6) x10² colony forming units per gram and three days fermented dry product is 9.4x10² - 1.2x10³ colony forming units per gram. This plate count assay can be used as an index to evaluate the microbial content, in order to provide a microbiological specification for the fermented cassava products. Fermented cassava products would be an ideal option that reduces the post-harvest losses of raw cassava.