Browsing by Author "Gonfa, Alemu"

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    Synergetic effects of Mandillo [Crassocephalum macropappum (Sch. Bip. ex. A. Rich.) S. Moore] during Enset fermentation: chemical nature and efficiency
    (Addis Ababa University, 2016-04) Gonfa, Alemu; Megersa, Negussie (PhD); Mehari, Tetemke (PhD); Muleta, Diriba (PhD); Young-Mog, Kim (Professor)
    Enset (Ensete ventricosum (Welw.) Cheesman) is an ornamental plant in Asia, widely distributed in Africa and cultivated only in some regions of Ethiopia. Enset plant withstands prolonged period of drought and known for its high yielding potential. Fermentation of Enset produces a starchy food named Kocho, however, it is not practiced extensively. The principal reasons for low popularity of Enset are its uncommon sensory attributes among non-Enset consuming people, short shelf-life, nutrient losses, long fermentation period and lack of awareness. In Ethiopia, the Shekacho society adds Mandillo (Crassocephalum macropappum (Sch. Bip. ex. A. Rich.) S. Moore) stem during traditional Enset fermentation without knowing its scientific significance to the fermentation processes. Thus, the present study was initiated with the main purposes of investigating the indigenous knowledge of Shekacho society in Enset cultivation, Kocho consumptions, bioactive components of Mandillo parts and to determine its effects in Enset fermentation processes. The study was conducted using standard methods. To evaluate the indigenous knowledge of Shekacho society, analytical data were collected using semi-closed questionnaire, field observations, interviews and discussion with key informants with local annotations review. Enset plant physical structures were assessed. Phytochemical composition of Mandillo was evaluated. Its DNA damage protective and antioxidant activities were analyzed. Antimicrobial activity of Mandillo was tested against standard bacterial and yeast strains. Cytototoxicity of Mandillo was also evaluated. Fermentation process was carried out from 0-90 days. The pH value, titratable acidity, lactic acid and acetic acid contents were measured. Microbial counts were made on their respective agar media. Lactic acid bacteria (LAB) and yeast isolates were identified using morphological, biochemical and molecular techniques. Proximate composition, mineral contents, phytic acid, tannin, water holding capacity, and sensory attributes iii of Kocho were evaluated and the main findings are described as follows. The descriptive analysis of the data and the corresponding results indicated the existence of a high degree of consistency among the respondents with regard to Enset histories, fermentation processes, productivity, shelf-life of Kocho and food preparation. About 115 Enset cultivars were identified. Phytochemical analysis of Mandillo showed the presence of saponins, tannins, anthraquinones, steroids, terpenoids and flavonoids. Total phenolic and flavonoid contents of the aerial part calculated as 101.48 mg GAE (Gallic acid equivalent)/g and 293.25 mg QE (Quercetin equivalent)/g, respectively. Mandillo showed strong 2, 2-diphenyl-1-picryl hydrazyl (DPPH) scavenging potential with IC50 ≤ 50 μg/mL. The stem of Mandillo showed promising protective activity against oxidative DNA damage. The minimum inhibitory concentration of stem against E. coli KCTC 1682 and Candida utilizes KCCM 11355 was ≥ 15.62 μg/mL. The final pH of Kocho fermented with starter culture but no Mandillo (Koki) and with Mandillo (Kom) decreased to 4.49 and 4.10; respectively, which are significantly different and didn’t allow the growth of spoilers in Kom. Titratable acidity, lactic acid and acetic acid contents of Kom increased by 64.34%, 103.90% and 40.04%, respectively when compared to Koki. Koki and Kom samples had LAB counts of 1.16×107 and 2.83×108 CFU/g, respectively, on the day 37. Treatments with Mandillo stem significantly (p < 0.05) lowered counts of aerobic mesophilic bacteria, aerobic spore formers and coliforms. Staphylococci were below detectable level. The 16S rRNA gene sequences analysis and phylogenetic tree reconstruction identified LAB species as Lactobacillus plantarum (69.37%), Leuconostoc mesenteroides (9.91%), Lac. paracasei (9.01%), Lac. brevis (3.60%) and other rare species. Lac. paracasei and Lac. brevis were dominantly found in Kom during the final days of fermentation. An 18S rRNA gene sequences evaluation identified yeast isolates as Candida boidinii (30%), Wickerhamomyces sp. ES22S03 (16%), Pichia fermentans (16%), Williopsis sp. (10%) as dominate species and others minor strains. Kocho composition analysis showed significant (p < 0.05) differences between Koki and Kom in moisture contents (8.34 to 8.80%) and (9.14 to 7.95%), fiber (7.92 to 5.56%) and (6.25 to 3.96%), protein (3.24 to 3.68%) and (3.59 to 3.95), phytic acid (5.83 to 4.11 mg/g) and (4.95 to 4.33 mg/g), water holding capacity (8.55% and 6.37%); respectively. Mineral contents of Koki and Kom also calculated as Ca (9.84 mg/100 g and 10.08 mg/100 g), Fe (2.12 mg/100 g and 2.08 mg/100 g), Zn (1.99 mg/100 g and 1.77 mg/100 g) and Cu (0.12 mg/100 g and 0.16 mg/100 g); respectively. Sensory evaluation revealed overall acceptability values of 73.27% (Koki) and iv 97.20% (Kom). Cytotoxicity evaluation of Mandillo stem against Raw Cells 264.7 showed no toxicity at ≤ 4 μg/mL. From the results of the descriptive analysis of the data and the corresponding results suggested by the respondents, it is understood that Enset is very important for food security and environmental protection. Phytochemical contents and activities of Mandillo revealed consistency with the starter culture role played by the addition of the stem part of the plant. The effect of adding Mandillo during Enset fermentation showed significant differences in all of the measured Kocho quality parameters, food composition, microbial dynamics and diversities and sensory attributes of experimental Kocho product compared to the control sample. In general, improvements of the basic components of Kocho dough are responsible for the enhancement of its shelf-life, safety and sensory attributes of the food as a result of good fermentation processes. In the light of the current finding, extensive investigation are required to qualify Mandillo as food preservative and shelf-life enhancer for its application in food sectors.