Masters Degree Dissertations

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Browsing Masters Degree Dissertations by Subject "Coffea arabica."

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    Fatty acid composition of oils from green coffee beans from different agro-ecological zones of Uganda
    (Kyambogo University(Unpublished work), 2018-11) Mugabe, Amos
    Coffee is an important agricultural commodity and beverage widely consumed throughout the world. Two-thirds of Ugandans depend on coffee as an important source of income. The quality of coffee determines the relative price and its end use. The lipid composition has been used to characterize Arabica and Robusta coffee. Oil yield, fatty acid (FA) composition and oil nutritional quality of green coffee beans; arabica coffee (Coffea arabica) from Bugisu, Rwenzori, Kisoro and Maracha, and robusta coffee (Coffea canephora var. robusta) from Iganga, Ibanda, Rukungiri, Mbarara, Ntungamo, Masaka, Kayunga and Luwero coffee regions of Uganda were determined. Green coffee beans were obtained from Uganda Coffee Development Authority (UCDA) and coffee dealers in Iganga, Luwero, Kisoro and Maracha Districts. Oil was extracted in a Soxhlet apparatus using n-hexane. Fatty acids were determined as the FA methyl esters (FAME) using flame ionization detection gas chromatography. Differences in oil yield were analysed by ANOV A. The PUF A/SaF A, MUF A/SaF A, (PUF A +MUF A)/SaF A and PUF A/MUF A ratios were used to evaluate the nutritional quality of the oil. Oil yield ranged between 1. 75 and 15 .45%. Arabica coffee from Bugisu gave a significantly (p < 0.05) higher oil yield. Robusta coffee from Ntungamo gave the lowest mean oil yield. Unsaturated fatty acids (UFA) predominated over saturated fatty acids (SaFA). Linoleic and oleic acids were the main unsaturated fatty acids accounting for 53% of the total. Palmitic acid was the major SaFA. Oil yield and FA composition were dependent on agro-ecological coffee sample source and coffee variety. Based on the obtained nutritional quality indices, green coffee oil can be used in foods on blending with other oils. Nevertheless, there is need to investigate the existence of the transfatty acids in green coffee oil. KEY WORDS: Coffea arabica, Coffea canephora, fatty acid, green coffee beans, oil yield
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    Potential of spontaneous microbial fermentation isolates to improve fermentation and cup quality of wet processed Arabica coffee (coffea arabica)
    (Kyambogo University, 2021-07) Mugerwa, Fredrick
    Spontaneous wet processing of coffee currently practiced in Uganda is constrained by long processing times, losses, and inferior quality coffees. Starter cultures are nowadays used to control fermentation of foods. This study evaluated the predominant yeasts and bacteria in the spontaneous fermentation of Arabica coffee (Coffea arabica) from Bugisu and their potential use as starter cultures in the wet fermentation of coffee. A total of 21 samples of the fermenting mass of Arabica coffee (100 ml each) were used for isolation of predominant yeasts and bacteria during spontaneous fermentation. The isolates were grouped by cell morphology and biochemical features and then subjected to polymerase reaction (PCR) for confirmation of species. Genomic DNA of the organisms was extracted and the variable region 3 of 5.8S and 16S rRNA genes for yeast and bacteria respectively were amplified PCR using universal primers ITS1 and ITS4, and P16S and M26S, respectively. Representative isolates from each PCR profile were identified by sequencing using Sanger sequencing and the closest known relatives of the sequences obtained were retrieved from the National Centre for Biotechnology Information data base using a Basic Local Alignment Search Tool (BLAST). The predominant microorganisms were enriched and their effects on the fermentation process were determined. Controlled fermentation of pulped Arabica coffee (100 kg) was carried out. Physicochemical changes namely pectin, total soluble sugars, viscosity, hydrogen potential and titratable acidity were monitored in the fermenting mass using standard AOAC and ISO methods. Coffee beans from the controlled fermentation experiments were roasted at 210oC for 10 min, to medium dark roast profile and evaluated for the cup quality using the Specialty Coffee Association (SCA) cupping protocol. The yeasts Kazachstania exigua and Pichia kudriavzevii, and the bacteria Leuconostoc mesenteroides and Paenibacillus campinasensi were the predominant spp. in the in the spontaneous fermentation of C. arabica in Bugisu sub region. Mixed cultures performed better than single cultures in promoting fermentation.