Department of Food Science and Technology

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Studies on the optimization of immobilising acetogenic and methanogenic biomass on polyurethane carrier
(. Fac. Landbouw. Rijksuniv. Gent, 1989) Rubindamayugi, M.S.T.; Broeders, P.; op den Camp, H.J.M.; Lubberding, H.J.; Vogels, G.D.
The influence of operational conditions (including the specific substrate concn in the feed, the hydraulic retention time and wastewater composition) on the rate of immobilization of acetogenic and methanogenic bacteria in an anaerobic polyurethane carrier reactor (PCR) treating synthetic Volatile Fatty Acids (VFA) based wastewater was investigated. The performance of continuous and fed batch culture reactor systems had a roughly similar start up period and biogas production rate. Preliminary results indicated that these systems started up within 8 d of operation. A max. concn of 151 mM acetate and 126 mM propionate was applied in the reactors treating VFA based wastewaters with a higher proportion of acetate and propionate, respectively. In all reactors a max. concn of 45.4 mM butyrate was applied. At max. acetate concn no toxic effect on acetogenic and methanogenic biomass activity were observed. The max. propionate concn showed strong inhibitory effect on biomass activity. At the max. feed concn the VFA conversion, methane production rate and methane content decreased. Biomass activiy tests showed that the reactors fed with a higher acetate concn showed higher acetogenic and methanogenic activity than the reactor treating wastewater with higher propionate concn. The influence of operational conditions on biomass washout were also investigated.
The development of ice crystals in food products during the superchilling process and following storage, a review
(Elsevier, 2014-10) Kaale, Lilian Daniel; Eikevik, Trygve Magne
Superchilling is a method of preserving food by partial ice crystallization. The ice stored in superchilled products will be used as a cold reservoir during distribution or storage. Chemical and physical changes such as low water holding capacity, increase in product drip loss may occur during superchilled storage. There is a need to study the factors which may influence on these changes. The information on the development of ice crystals during the superchilling process and following storage, which has a large influence on the quality of the final superchilled food, is useful for the industry in estimating the refrigeration requirements for a superchilling system and designing the necessary equipment.
Physical properties of extruded snacks enriched with soybean and moringa leaf powder
(International Research Journals, 2015-01) Rweyemamu, Leonard, M.P.; Yusuph, Athuman; Mrema, Godwill, D.
This study was conducted to investigate the application of extrusion cooking in the production of snacks containing soybean (SB) and Moringa oleifera (MO) leaves as inexpensive sources of micronutrients. The specific objectives were to examine effects of barrel temperature, residence time and moisture content of feed on selected physical properties of extruded snacks (extrudates), namely water absorption index (WAI), water solubility index (WSI) and expansion ratio (ER). The extrudates were obtained by blending different levels of input ingredients of maize flour (MF) (55 to 80%), full fat soybean flour (FFSF) (10 to 30%), and Moringa oleifera leaf powder (MOLP) (5 to 15%). Extrusion process variables in a twin-screw extruder were at three levels for temperature (100, 130 and 160°C), feed moisture content (15, 22.5 and 30%), and residence time (60, 75 and 90 s). The performed study revealed that the level of incorporation of both FFSF and MOLP, and feed moisture content have significant effects on the expansion ratio, water solubility index and water absorption index of the extrudates. It was concluded that the role of processing conditions and blending levels have a significant contribution to the quality characteristics of the soy-moringa expanded snacks.
Antimicrobial Properties and Mechanism of Action of Some Plant Extracts Against Food Pathogens and Spoilage Microorganisms
(Frontiers in Microbiology, 2018-07-24) Gonelimali, Faraja Deo; Jiheng, Lin; Wenhua, Miao; Jinghu, Xuan; Fedrick, Charles; Meiling, Chen; Shaimaa, Hatab R
This work aims to evaluate the antimicrobial potential of ethanolic and water extracts of roselle (Hibiscus sabdariffa), rosemary (Rosmarinus officinalis), clove (Syzygium aromaticum), and thyme (Thymus vulgaris) on some food pathogens and spoilage microorganisms. Agar well diffusion method has been used to determine the antimicrobial activities and minimum inhibitory concentrations (MIC) of different plant extracts against Gram-positive bacteria (Bacillus cereus, Staphylococcus aureus), Gram-negative bacteria (Escherichia coli, Salmonella enteritidis, Vibrio parahaemolyticus, and Pseudomonas aeruginosa), and one fungus (Candida albicans). The extracts exhibited both antibacterial and antifungal activities against tested microorganisms. Ethanolic roselle extract showed significant antibacterial activity (P < 0.05) against all tested bacterial strains, while no inhibitory effect on Candida albicans (CA) was observed. Only the ethanolic extracts of clove and thyme showed antifungal effects against CA with inhibition zones ranging from 25.2 ± 1.4 to 15.8 ± 1.2 mm, respectively. Bacillus cereus (BC) appears to be the most sensitive strain to the aqueous extract of clove with a MIC of 0.315%. To enhance our understanding of antimicrobial activity mechanism of plant extracts, the changes in internal pH (pHint), and membrane potential were measured in Staphylococcus aureus (SA) and Escherichia coli (EC) cells after exposure to the plant extracts. The results indicated that the plant extracts significantly affected the cell membrane of Gram-positive and Gram-negative bacteria, as demonstrated by the decline in pHint as well as cell membrane hyperpolarization. In conclusion, plant extracts are of great value as natural antimicrobials and can use safely as food preservatives
Co-composting of banana peel and orange peel waste with fish waste to improve conversion by black soldier fly (Hermetia illucens (L.), Diptera: Stratiomyidae) larvae
(Elsevier, 2021-08-11) Isibika, Alice; Vinnerås, Björn; Kibazohi, Oscar; Lalander, Cecilia; Christian, Zurbrügg
Black soldier fly (BSF) larvae composting is a promising waste treatment that can add value to available biodegradable waste. However, substrates that have low protein content and contain complex molecules (e.g. fruit peels) are not easily degraded by the larvae. This study evaluated the impact on the BSF larvae composting efficiency of co-composting different mixtures of banana and orange peels with incremental increase of fish waste. Mixtures (in total 50 distinct mixtures) of varying proportions of banana peels, orange peels and fish waste were evaluated. BFSL fed on orange peel and banana peel mixtures, containing no fish waste, resulted in a lower biomass conversion efficiency (4.5% ± 1.3) on a volatile solids (VS) basis (BCEvs). Co-composting the fruit peels with fish waste increased the biomass conversion efficiency and the highest BCEvs (25%) was attained when 75% fish waste was included. However, the BCEvs varied greatly (18.0% ± 5.8), likely due to varying fish waste composition. A 25% fish waste inclusion resulted in more than twice as high BCEvs (12.3% ± 2.1) compared to when no fish waste was included. As the conversion efficiency variance increased with increasing fish waste inclusion, it was recommended to keep the inclusions of the fish waste to around 25% of the total mixture, in order to increase the reliability of the BSF larvae composting efficiency.
Effects of Ripeness and Blending Speed on the Extraction Yield and Physical Chemical Properties of Low Viscosity Banana Juice
(College of Natural and Applied Sciences, University of Dar es Salaam, 2021-12) Kibazohi, Oscar; Matabura, Victor V
Low viscosity banana juice can be extracted from banana by blending and pressing the resulted semi-solid pulp to separate the juice. This juice extraction technology is relatively new and further studies to understand key parameters for juice release is vital for scaling up production and commercialisation. This study, investigated the influence of blending speed and ripeness stage on banana juice yield using two banana cultivars; the East African highland banana (Mbile) and the exotic banana (Pisang awak). Types of sugars and organic acids in the juice were analysed using an HPLC. Changes with ripening of fruit firmness, juice pH and soluble solids were also examined. The juice yield increased significantly (p < 0.05) with increasing blending speed and ripeness stage for all cultivars. The Mbile cultivar from Kagera had the highest juice yield of 82.35%, followed by Mbile cultivar from Kilimanjaro with 75.30% and Pisang awak cultivar with juice yield of 62.50%. The highest juice yield for all cultivars was achieved at 3500 rpm blending speed and ripeness stage 5. Fructose and glucose sugars increased significantly (p < 0.05) with ripeness, while sucrose showed insignificant changes. Malic and citric acids were observed to increase significantly (p < 0.05) during ripening in all banana cultivars.
Physico-chemical Properties of Mechanically Extracted Banana Juice at Different Ripening Stages
(College of Natural and Applied Sciences, University of Dar es Salaam, 2021-12) Mathias, Mathayo G; Kaale, Lilian D; Kibazohi, Oscar
This paper presents the findings of a study on physico-chemical properties of low viscosity banana juice from five banana cultivars: Pisang Awak (PSA) an ABB genome, Yangambi km5 (YKM5) an AAA genome and cultivars from AAA-EA genome, namely Mbilabile, Ndeshi and Mlonga. Low viscosity banana juice was extracted using improved mechanical method at five ripening stages. The physico-chemical properties significantly varied according to cultivars and ripening stages (p < 0.05). Yields, total soluble solids (TSS), titratable acidity (TA) and pH were in the range of 19.50–74.03%, 7.33–27.64 oBrix, 0.37–0.76% malic acid equivalent and 4.09–4.70, respectively. Yields decreased in the order of Mbilabile > Ndeshi > Mlonga > YKM5 > PSA whereas the total soluble solids increased as follows Mlonga < Mbilabile < Ndeshi < YKM5 < PSA. Furthermore, ashes and mineral contents decreased with ripening stages whereas the low viscosity banana juice was rich in potassium and magnesium. Finally, the study recommends stage 5 of the ripeness as ideal for producing low viscosity banana juice.
Proximate composition, pasting and functional properties of composite flour blends from cassava and chia seeds flour
(Sage Publications, 2021-12-07) Rweyemamu, Leonard MP; Kibazohi, Oscar; Katunzi-Kilewela, Ashura; Kaale, Lilian D; Fortunatus, Roman M
The study established the proximate composition, pasting, and functional properties of cassava flour (CF) blended with chia seeds flour (CSF). Composite flour was prepared by blending CF with CSF in the ratios of 95:05, 90:10, 85:15, 80:20, and 75:25 with CF and CSF used as controls, respectively. The effect of blending significantly (p < 0.05) increased protein, fat, fibre, and ash contents as CSF increased. On other hand, moist- ure and carbohydrate contents decreased significantly. Pasting properties of composite flour blends decreased significantly (p<0.05) as the incorporation of CSF increased and a noticeable change was observed for composite flour (75:25) except for peak time and pasting temperature. Functional properties of water absorption capacity (WAC) of CSF were significantly different with CF and composite flour blends. Oil absorption capacity (OAC) of CF and CSF were significantly different, while the composite flour blends had varied OAC due to the inclusion of the different amounts of CSF. The swelling capacity (SC) of CF and CSF were not significantly different, but composite flour blends were significantly different from both CSF and CF. The least gelation concentration (LGC) and bulk density (BD) increased significantly as chia seeds increased. Increased concentration of chia CSF in the composite flour blends showed to alter the functional properties. This study recommends composite flour 75:25 for processing semiliquid products like porridge due to reduced pasting properties values that may be associated with increased energy density compared to CF.
Sensory profile, consumer acceptability and preference mapping of cassava-chia seeds composite porridges
(Elsevier, 2021-12-26) Katunzi-Kilewelaa, Ashura; Mongi, Richard; Kaale, Lillian D; Kibazohi, Oscar; Fortunatusa, Roman M; Rweyemamu, Leonard MP
This study applied quantitative descriptive analysis, hedonic test, and preference mapping techniques to inves- tigate the sensory profile, consumer acceptability, and drivers for consumer acceptability of cassava-chia seeds composite porridge samples. Chia seeds flour was developed and blended with cassava flour at varying propor- tions (0, 5, 10, 15, 20, and 25%) to make six composite porridges labelled CF, CCSF1, CCSF2, CCSF3, CCSF4, and CCSF5. The control cassava porridge (CF) formulation had significantly (p <0.05) higher sweetness and aroma intensities than the composite formulations. Conversely, the CCSF4 (20%) and CCSF5 (25%) composite formulations had significantly (p < 0.05) higher colour, mouthfeel, and oiliness intensities than the control for- mulation (CF). Furthermore, when compared to cassava porridge, the overall acceptability of composite porridge samples was significantly (p <0.05) much greater. Consumer preference for CCSF5 was much greater than for CF, although sample CCSF5 did not differ significantly (p > 0.05) from other composite porridge blends (sample CCSF1, CCSF3, and CCSF4). Consumer preferences for porridge formulations were largely driven by colour, tex- ture, and oiliness attributes. Thus, mixing up to 25% chia seeds flour with cassava flour produces a composite porridge with enhanced sensory properties and, hence, more consumer appeal than non-mixed cassava porridge. Significantly, this study creates an opportunity for small to large-scale food processors to valorise cassava flour by producing cassava-chia seeds composite flour to benefit the broader population in terms of food security and nutritional enhancement.
Aflatoxin B1 variations in animal feeds along the supply chain in Tanzania and its possible reduction by heat treatment
(Taylor & Francis, 2022-03-04) Mwakosya, Anjelina W; Limbu, Samwel M; Majaliwa, Nuria; Zou, Xiaobo; Shi, Jiyong; Kibazohi, Oscar
This study evaluated the presence of aflatoxin B1 in five different animal feeds collected from manufacturers, suppliers and consumers and its possible reduction by heating at 100°C for 180 min. A total of 160 animal feed samples were collected and analyzed by using lateral flow immunoassay method. The results revealed that all animal feeds analyzed were positive for aflatoxin B1 with 91% samples containing high concentrations ranging from 24.00 to 76.23ng/g above the international allowable standard for animal feeds (20 ng/g). Maize bran (76 ng/g) and sunflower cake (63 ng/g) had higher aflatoxin B1 concentrations, correlating with higher moisture content. Upon heating the feeds, aflatoxin B1 was reduced to a concentration ranging from 2.24 to 9.78 ng/g (<20 ng/g). Our study suggests high potential health problems to animals and humans from aflatoxins requiring proper heating and frequent monitoring of the animal feeds for aflatoxin B1.

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