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Assessment of the physico-chemical and sensory properties of frozen fillets of tuna and tunarelated fish species marketed along the Tanga and Mtwara coastlines, Tanzania
(Taylor & Francis, 2022-11-10) Lujuo,E.J.; Mkupasi, E.M.; Lamtane,H.A.
Tuna and tuna-related fish are valuable marine species lacking standardized quality assessment parameters. This study assessed the physico-chemical and sensory properties of skipjack (Katsuwonus pelamis), bigeye (Thunnus obesus), yellowfin (Thunnus albacares), and kawakawa (Euthynnus affinis) tuna fish fillets marketed in Tanga and Mtwara, Tanzania. Laboratory AOAC methods evaluated total volatile basic-nitrogen (TVB-N), pH, color (lightness L*), and texture (hardness) properties. The quality index method (QIM) assessed tuna fillets’ sensory properties (color, texture, and odor). The pH ranged between 5.60 ± 0.08 and 6.10 ± 0.30, the TVB-N between 34 ± 7.00 mg/ 100 g and 38.04 ± 10.50 mg/100 g, color lightness (L*) between 24.33 ± 1.82 and 40.10 ± 1.50, and texture (hardness) from 3.84 ± 1.20 N to 8.56 ± 1.84 N. The tuna fillets got an overall score of 2 in the sensory analysis, which indicated good quality according to the QIM. Furthermore, the present study showed significant differences (p < .05) between the tuna species in pH, hardness (instrumental), and color lightness properties (L*). There were no significant differences (p > .05) in average TVB-N results across all tuna fillets. There were significant correlations among the assessed quality properties. Based on the combined quality properties results and correlation analysis, the tuna and tuna-related fish marketed in the study areas were of good quality. This study recommends the establishment of standardized quality assessment parameters for tuna and related fish species.
Modeling the Effects of Human Awareness and Use of Insecticides on the Spread of Human African Trypanosomiasis: A Fractional-Order Model Approach
(Licensee MDPI, Basel, Switzerland., 2025-09-22) Koga, Oscar; Helikumi, Mlyashimbi; Mayengo, Maranya; Mhlanga,Adquate
In this research work, we proposed and studied a fractional-order model for Human African Trypanosomiasis (HAT) disease transmission, incorporating three control strategies: health education campaigns, prevention measures, and use of insecticides. The theoretical analysis of the model was presented, including the computation of disease-free equilibrium and basic reproduction number. We performed the stability analysis of the model and the results showed that the disease-free equilibrium point was locally asymptotically stable whenever R0 < 1 and unstable when R0 > 1. Furthermore, we performed parameter estimation of the model using HAT-reported cases in Tanzania. The results showed that fractional-order model had a better fit to the real data compared to the classical integerorder model. Sensitivity analysis of the basic reproduction number was performed using computed partial rank correlation coefficients to assess the effects of parameters on HAT transmission. Additionally, we performed numerical simulations of the model to assess the impact of memory effects on the spread of HAT. Overall, we observed that the order of derivatives significantly influences the dynamics of HAT transmission in the population. Moreover, we simulated the model to assess the effectiveness of proposed control strategies. We observed that the use of insecticides and prevention measures have the potential to significantly reduce the spread of HAT within the population.
Insect-pollinators and their interactions with plants differ in disturbed and semi-natural areas: Tanzania’s Southern Highlands case study.
(SCIENCE PROGRESS, 2023) Ojija, Fredrick; S Adam, Lusekelo; Nicholaus , Regan
Due to inadequate insect-pollinator data, particularly in sub-Saharan African countries like
Tanzania, it is difficult to manage and protect these species in disturbed and semi-natural areas.
Field surveys were conducted to assess insect-pollinator abundance and diversity and their interactions
with plants in disturbed and semi-natural areas in Tanzania’s Southern Highlands using pan
traps, sweep netting, transect counts, and timed observations techniques. We found that species
diversity and richness of insect-pollinators were high in semi-natural areas, and there was 14.29%
more abundance than in disturbed areas. The highest plant-pollinator interactions were recorded
in semi-natural areas. In these areas, the total number of visits by Hymenoptera was more than
three times that of Coleoptera, while that of Lepidoptera and Diptera was more than 237 and
12 times, respectively. Hymenoptera pollinators had twice the total number of visits of
Lepidoptera, and threefold of Coleoptera, and five times more visits than Diptera in disturbed
habitats. Although disturbed areas had fewer insect-pollinators and fewer plant–insect–pollinator
interactions, our findings indicate that both disturbed and semi-natural areas are potential habitats
for insect-pollinators. The study revealed that the over-dominant species Apis mellifera could influence
diversity indices and network-level metrics in the study areas. When A. mellifera was
excluded from the analysis, the number of interactions differed significantly between insect orders
Halotolerant Pseudomonas koreensis S4T10 mitigate salt and drought stress in Arabidopsis thaliana
(Physiologia Plantarum, 2023-11) Nathanael Kalleku, Justine; Ihsan, Samsoor; Ibrahim Al-Azzawi, Tiba Nazar
Salt and drought are documented among the most detrimental and persistent abiotic
stresses for crop production. Here, we investigated the impact of Pseudomonas koreensis
strain S4T10 on plant performance under salt and drought stress. Arabidopsis thaliana
Col-0 wild type and atnced3 mutant plants were inoculated with P. koreensis or tap water
and exposed to NaCl (100 mM) for five days and drought stress by withholding water
for seven days. P. koreensis significantly enhanced plant biomass and photosynthetic pigments
under salt and drought stress conditions. Moreover, P. koreensis activated the antioxidant
defence by modulating glutathione (GSH), superoxide dismutase (SOD),
peroxidase (POD), and polyphenol oxidase (PPO) activities to scavenge the reactive oxygen
species produced due to the stress. In addition, the application of P. koreensis upregulated
the expression of genes associated with antioxidant responses, such as AtCAT1,
AtCAT3, and AtSOD. Similarly, genes linked to salt stress, such as AtSOS1, AtSOS2,
AtSOS3, AtNHX1, and AtHKT1, were also upregulated, affirming the positive role of
P. koreensis S4T10 in streamlining the cellular influx and efflux transport systems during
salt stress. Likewise, the PGPB inoculation was observed to regulate the expression of
drought-responsive genes AtDREB2A, AtDREB2B, and ABA-responsive genes AtAO3,
AtABA3 indicating that S4T10 enhanced drought tolerance via modulation of the ABA
pathway. The results of this study affirm that P. koreensis S4T10 could be further developed
as a biofertilizer to mitigate salt and drought stress at the same time.
Assessment of Heavy Metals in Wild and Farmed Tilapia (Oreochromis Niloticus) on Lake Kariba, Zambia: Implications for Human and Fish Health
(Taylor & Francis, 2022) Simukoko, Chalumba K.; Mwakalapa, Eliezer B.; Bwalya, Patricia; Muzandu, Kaampwe; Berg, Vidar; Mutoloki, Stephen; Polder, Anuschka; Lyche, Jan, L.
The aim of this study was to assess the levels of heavy metals in both wild and farmed tilapia on
Lake Kariba in Zambia and to evaluate the impact of intensive fish farming on wild tilapia. Three
sites for wild fish (2 distant and 1 proximal to fish farms) and two fish farms were selected. One
hundred fish (52 from distant sites; 20 near fish farms; 28 farmed fish) were sampled and muscle
tissues excised for analysis of heavy metals (Mg, Fe, Zn, Al, Cu, Se, Co, Mo, As, Cr, V, Ni, Hg, Pb, Li, Cd,
and Ag) by acid (HNO3) digestion and ICP-MS. All metals were found to be below the maximum
limits (MLs) set by WHO/EU. Essential metals were higher in farmed tilapia, whereas non-essential
metals were higher in wild tilapia. Significantly higher levels of essential metals were found in wild
fish near the fish farms than those distant from the farms. Estimated weekly intake (EWI) for all
metals were less than the provisional tolerable weekly intakes (PTWI). Target hazard quotients
(THQ) and Hazard Indices (HI) were <1, indicating no health risks from a lifetime of fish consump-
tion. Selenium Health Benefit Value (HBVSe) was positive for all locations, indicating protective
effects of selenium against mercury in fish. Total cancer risk (CR) due to As, Cr, Cd, Ni and Pb was less
than 1 × 10−4, indicating less than 1 in 10,000 carcinogenic risk from a lifetime consumption of
tilapia from Lake Kariba. Hg levels (0.021 mg/kg) in wild tilapia at site 1 were higher than the
Environmental quality standard (EQS = 0.020 mg/kg) set by EU, indicating possible risk of adverse
effects to fish. Except for Hg, levels of metals in fish were safe for human consumption and had no
adverse effects on fish.