Browsing by Author "Assaye, Hirut"

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    Microbiological Quality and Safety of Commercially Produced Sausages in Addis Ababa
    (Addis Ababa University, 2006-06) Assaye, Hirut; Ashenafi, Mogessie (Professor)
    The microbiological quality and safety of emulsion type small diameter (frankfurter) and large diameter (mortadella) sausages purchased from different supermarkets in Addis Ababa, Ethiopia, were investigated between November, 2004 and December, 2005. A total of 210 sausage samples consisting of 120 small diameter (30 each of pork, beef, veal and chicken) and 90 large diameter (30 each of pork, veal and chicken mortadella) sausage samples were included in the study. The majority of sausages had pH values above 6.00 with mean values ranging between 6.11 and 6.33. The moisture content values of small diameter sausages ranged between 32% and 46% and those of large diameter sausages ranged between 31 % and 63%. With regard to the microbial load of small diameter sausages, more than 53% of pork, 87% of beef, 57% of veal and 40% of chicken sausage samples had aerobic mesophilic counts 2:log 5 cfu/g. Enterobacteriaceae were frequently encountered in these sausage samples and more than half of beef and veal sausage samples had Enterobacteriaceae counts 2: log 4 cfu/g. The majority of pork, beef and veal sausage samples also harbored coliforms. Furthermore, more than 40% of veal sausage samples had coliform counts 2:log 4 cfu/g. On the other hand, coli forms were rarely detected in chicken sausage samples. Enterococci were encountered in 60% of pork, 100% of beef and in more than 70% of veal and chicken sausage samples with counts ranging from log 2 to log 6 cfu/g. About 26% of pork, 60% of beef and 38% of veal sausage samples had Staphylococcus counts 2:log 5 cfu/g. All sausage samples harbored LAB and more than 73% of pork, 60% of beef and about 40% of veal sausage samples had counts 2:log 7 cfulg. Over 86% of pork, 93% of beef, 38% of veal and 31 % of chicken sausage samples had yeast counts 2: log 4 cfulg. In the case of large diameter sausages or mortadellas, about 53% of pork, 48% of veal and 40% of chicken mortadella samples had aerobic mesophilic counts 2: log 5 cfu/g, thus exceeded the typical aerobic mesophilic count value set for ready-to-eat foods. Enterobacteriaceae were encountered in more than 60% of pork, 50% of veal and 45% of chicken mortadella samples with counts between log 2 and log 4 cfu/g. More than 50% of pork and about 33% of veal and 40% of chicken mortadella samples had also coliform counts between log 2 and log 4cfu/g. The majority of large diameter sausages harbored enterococci and staphylococci. LAB were encountered in all mortadella samples and 40% of pork and more than 30% of veal and chicken mortadella samples had counts :::Iog 6 cfu/g. The majority of mortadella samples contained yeasts and more than 45% of pork, 40% of veal and 30% of chicken mortadella samples had counts::: log 4 cfu/g. The aerobic mesophilic flora of both small and large diameter sausages was dominated by Gram-positive organisms, with Bacillus being the most dominant species in both types of sausages. Salmonel/a was isolated from four (1.9%) samples consisting of two small diameter sausages and two mortadellas. During aerobic storage of small diameter sausage samples and sliced mortadella samples at ambient temperature, both types of sausages spoiled within three to four days. At refrigeration storage, small diameter sausages spoiled within 12 to 16 days and mortadella samples spoiled within 12 to 20 days of storage. Spoilage in small diameter sausage samples was manifested as slime formation and off-odor development whereas spoilage in sliced mortadella samples was manifested as green discoloration and off-odor development. In general, the majority of sausage samples investigated in this study had high microbial load. Time temperature abuse during processing or post-cooking contamination due to improper handling of the products or inadequate storage conditions or a combination of these factors may contribute to high microbial counts. Furthermore, the absence of microbiological control system or the end product, the raw material, or the other ingredients, at any stage of production and the poor sanitalY condition of some processing plants revealed inadequacies conceming quality and safety of these products. Key words/ phrases: Addis Ababa, Frankfurters, mortadella, quality, safety, Salmonel/a, sausage, supermarket
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    Quality and Safety Evaluation of Spirulina (Arthrospira) Biomass Harvested from an Ethiopian Soda Lake, Lake Chitu for Possible Applications in Human Nutrition
    (Addis Ababa University, 2014-12) Assaye, Hirut; Belay, Amha (Ass.prof.)
    The cyanobacterium Arlhrospira (Spirulina) is known for its high protein content and having various bioactive phytochemicals with potential health benefits. It is, therefore, produced worldwide either artificially or directly from natural lakes to be used as a dietary and/or protein supplement. Spirulina grows abundantly almost as a uni -algal population in an Ethiopian soda lake, Lake Chitu throughout the year. The objective of this study was to evaluate the nutrient profile and safety of Lake Chitu's Spirulina for possible applications in human nutrition. A one year study (March 2012-January 2013) was undertaken where sampling was done at two months interval. Variations were observed in the nutrient profile of the biomass on seasonal basis and in general wet season samples had relatively higher protein (47.9-55.7%) and low carbohydrates contents (30.9-36.4%) compared to dry season samples. Higher amino acids content was recorded for a wet season sample (86.4g/100g protein) compared to a dry season sample (62. l g/I00g protein). Variations were also observed in the fatty acid composition of Lake Chitu 's Spirulina as relatively higher proportion of unsaturated fatty acids were recorded for a sample harvested in wet season (61.8%) compared to a dry season sample (58.2%). Similarly, higher contents of phylonutrients (pigments) (mg g.I): chlorophyll a (8.2-10.3), phycobiliproteins (104.1-120.7), total carotenoids (3.17-4.31) and ~-carotene (1.24-1.61) were recorded for wet season samples. The mineral content of the biomass also varied according to season. While Na and K were found to be higher in the dry season sample, other major (Ca, P, Mg) and trace (Mn, Fe, Cu, Zn and Se) minerals were found in higher concentrations in the wet season sample. The safety of Lake Chitu's Spirulina was evaluated in terms of its microbial profile, heavy metals, pheophorbides, microcystin and nucleic acids content. Aerobic mesophilic count of the biomass ranged from 0.4 xl03 to 130 xl03 CFU/g for wet season and from 0.37 xlO3 to 15 xlO3 CFU/g for dry season samples. Counts of total coliforms, fecal coliforms, Ecoli, S. aureus, yeasts and molds were < 102CFU/g for both wet and dry season samples. Heavy metal contents of the biomass (mg kg-I) were: Pb (0.18), Cd (0.03), Hg (0.04) and As (18 .8). Pheophorbides content of the biomass were 16.2mg/100g and 22.3mg/J OOg for wet and dry season samplesrespectively. The nucleic acids content of the samples were 0.18 and 0.13% for wet and dry season samples respectively. Microcystins were not detected in both wet and dry season samples and short term feeding offreeze dried biomass (10 g/kg body weight) to mice didn't result any signs of toxicity or mortality. Phycobiliprotein-rich crude extract (PBE) was prepared from Spirulina and was evaluated for its chemical composition, amino acid profile, in vitro protein digestibility and functional properties for possible food applications. Phycobiliprotein-rich crude extract had higher contents of proteins (60.1 vs 45.2%) and amino acids (45.6 vs 39.0g/100gsample) than the crude Spirulina powder. Simi larly, in vitro protein digestibility value of PBE was higher (86%) than the crude Spirulina powder (59%) in a single enzyme assay. The extract had 50.5% protein solubility at pH 7 and 62.2% solubility at pH 12 although at this pH discoloration of the pigment was noted . PBE showed good emulsifying activity at neutral and basic pH regions and at higher protein concentrations the extract showed comparable emulsifYing activity with bovine serum albumin. Similarly, the foaming capacity and stability of PBE were high and comparable with the commonly used foaming agent, egg albumin. In conclusion, the nutrient profile of Lake Chitu's Spil'ulina is comparable with that reported for commercial Spirulina. Except arsenic which was found in higher concentrations, the biomass is safe in terms of other safety evaluation parameters and thus can potentially be used in human nutrition. In addition to using the whole biomass as a food supplement, high value products such as phycobiliproteins can be extracted from the crude biomass which can serve as a component in functional foods. Key words: Arthrospira, biomass quality, functional property, Lake Chitu, safety, season, phycobiliproteins, Spirulina