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Papers by richard mongi

SSRN Electronic Journal, 2022

Applied Food Research, 2022

Applied Food Research, 2021

African Journal of Food Science, 2021

Approximately 38% of Tanzanian children have vitamin A deficiency (VAD), and the majority of them... more Approximately 38% of Tanzanian children have vitamin A deficiency (VAD), and the majority of them do not have access to vitamin A-fortified foods. Orange-fleshed sweet potato (OFSP), a new crop in Tanzania, is rich in β-carotene, and could be a cheaper solution for VAD. The objectives of this study were to develop a type of Ugali (stiff maize porridge) fortified with OFSP, to correlate its β-carotene content (using colour measurement), and to assess its proximate composition and consumer acceptability. Ugali was prepared using maize flour with various amounts of added OFSP (0, 30, 50, 70 and 100%). Samples of Ugali with more OFSP had higher colour values (a* and b*) that imply the increase in β-carotene as the OFSP amount increased. The proximate compositions of Ugali with different amounts of OFSP were different (P<0.05). All samples that were made with the mixture of OFSP and maize flour have shown to have higher sensory scores than those with 100% maize or 100% OFSP; Ugali with 50% OFSP was most favourably rated by Tanzanian consumers. This sample was selected as a potential possibility for everyday consumption since it was shown to potentially supply more than 50% of the RDA of provitamin A for a specific age group. This supplementation method may be simple, affordable, and effective in reducing VAD in Tanzania.

The thermal performance of solar drying methods (cabinet direct, cabinet mixed-mode and tunnel dr... more The thermal performance of solar drying methods (cabinet direct, cabinet mixed-mode and tunnel drying), biochemical, sensory, rehydration and shelf-life qualities of mango banana, pineapple and tomato varieties were investigated in this study. Collector efficiencies and drying rates were computed and compared to measure the performance of dryers. The results showed tunnel dryer had significantly (p<0.05) higher efficiency (57.5%) with drying rates of 1.36, 1.17, 1.35 and 1.57 kg/h for mango, banana, pineapple and tomato, respectively than cabinet dryers with efficiency of 32.4-34.2% and drying rates of 0.11-0.13, 0.09-0.11, 0.11-0.13 and 0.17-0.22 kg/h for mango, banana, pineapple and tomato, respectively. Biochemical values varied significantly (p<0.05) between fresh and dried samples and between drying methods with fresh samples in all fruit and vegetable having higher total phenols (139.3±2.3-538.9±1 mgGAE/100g DM), antioxidant capacity (10.8±0.1-46.8±0.5 μmol/100g DM), pro...

Tanzania Journal of Agricultural Sciences, 2016

Honey is a sweet, yellowish liquid that is produced by honey bees and it has been used for many y... more Honey is a sweet, yellowish liquid that is produced by honey bees and it has been used for many years for nutrition and therapeutic purposes. Its therapeutic potential has been associated to its antioxidant capacity which plays an important protective role in human health through scavenging of free radicals in the human body and thereby decreases the amount of free radical and damage to biological molecules like lipids and DNA. This study was carried out to investigate the effect of floral source (miombo and acacia) and geographical origin (Central, Coastal, Lake, Northern, and Southern Highland) in mainland Tanzania on colour and antioxidant activity of honey samples. Colour, total flavonoids content (TFC), total phenol phenolic contents (TPC) and antioxidant activities of the samples were evaluated using UV/Vis spectrophotometer, Folin-Ciocalteu reagent and Ferric Reducing Antioxidant Power (FRAP) methods respectively. There were significant (p<0.05) differences in all paramete...

LWT, 2019

The effect of mango solar drying methods (traditional and tunnel dryers) on the quality of dried ... more The effect of mango solar drying methods (traditional and tunnel dryers) on the quality of dried mango slices was investigated by visible (VIS) and near-infrared (NIR) spectroscopy combined with the chemometric analysis methods of principal component analysis (PCA) and ANOVA-simultaneous component analysis (ASCA). Five batches of mango were investigated, each subjected to two/three different positions of three different types of dryers: electrical (reference), traditional, and tunnel dryers. The results of the visible and near-infrared spectra showed that the quality of the mango samples obtained from the electrical dryer (reference) was the most uniform and conserved the highest content of carotenoids and chlorophyll pigments. The samples from the traditional dryer had the highest variation and content of residual water. ASCA analysis of visible and shortwave near-infrared (VIS-NIR) (including color information) showed that the batch effect was most dominant with a significance effect of 47.5%, whereas longwave near-infrared (NIR) spectra (chemistry) showed that the dryer effect was the most dominant with a significance effect of 38.3%. The factor of the fruit positions in the dryers proved not to be significant. The VIS-NIR spectrum is thus well adapted to measure the fruit maturity and the NIR spectrum has great potential to investigate and control the dryer

African Journal of Biotechnology, 2017

Phytates and tannins are present in varying proportions in legume based foods. Investigation on t... more Phytates and tannins are present in varying proportions in legume based foods. Investigation on the effect of cooking on tannins and phytates was carried out on thirty eight raw and cooked bean (Phaseolus vulgaris) varieties. Tannins were assayed by vanillin-hydrochloric acid method, while phytates were determined by a method developed by Haugh and Lantzsch. There was a very high significant difference (P≤0.00001) in the tannin concentrations between the raw and cooked bean samples. The mean tannin content for the raw and cooked samples was 1.168±0.81 and 0.563±0.503%CE, respectively. Reduction of tannins after cooking ranged from 20%CE in M'mafutala to 81%CE in GLP 2 with an average reduction of 56.3%CE. Equally, there was a very high significant difference (P≤0.0001) in the phytate concentrations between the raw and cooked bean samples. The mean phytate content for the raw and cooked samples were 0.0219±002 and 0.0122±003 µg/mL, respectively. Cooking reduced the anti-nutritional factors significantly (p≤0.0001). The extent of antinutritional factors reduction varied between bean varieties. Cooking is therefore important for mineral absorption during digestion process in humans as it makes the minerals less bound and hence physiologically available.

Food chemistry, Jan 15, 2016

Tropical fruits contribute significantly to the total fruit intake worldwide. However, their meta... more Tropical fruits contribute significantly to the total fruit intake worldwide. However, their metabolomes have not yet been investigated comprehensively, as most previous studies revealed only volatile and bulk compositions. This study compares non-volatile metabolites of five fruits grown in Tanzania. A new methodology is developed for broad-spectrum GC-MS metabolomics in fruits using a new derivatization and a two dimensional peak deconvolution techniques. A total of 92 peaks were detected from fruits of which 45 were identified. Jackfruits contained the highest amount of carbohydrates, while baobab contained the highest amount of fatty acids. The highest content of organic acids was detected in tamarind. Principal component analysis revealed insights into metabolic differences and similarities, while hierarchical cluster analysis correctly grouped the fruits according to their relationships in plants' phylogenetic tree. The developed methodology could potentially be applied in...

Food Science and Quality Management, 2013

The harvesting practices, knowledge and post-harvest losses of fruits along the supply chain in B... more The harvesting practices, knowledge and post-harvest losses of fruits along the supply chain in Bagamoyo District were investigated. 142 farmers, 50 retailers and 10 wholesalers dealing with fruits were involved in the study. Data were collected using structured questionnaires. The results indicate that, 90.14% of the respondents harvested fruits when they are just ripe and the great market losses were reported to occur due to rotting (microbial) at 63%, physiological at 20% and 17% by insects and rodents. Along the supply chain, mechanical damage was observed to be the major type of loss during harvesting (79%) and transportation (56%) while microbial damage was observed by majority (67%) during marketing. Poor infrastructure from farm to the market was observed to account for large percentage of losses in the market. The findings also shows that all farmers (100%) interviewed have no knowledge on post-harvest losses and management. In the view of the findings, it can be concluded that, post-harvest handling practices and knowledge of stakeholders involved in fruit sub sector in the country are not good enough to prevent the losses. It is therefore imperative to improve educational knowledge, skills and fruits quality from the field to reduce post-harvest losses.

Descriptive sensory characteristics, consumer liking and preference mapping of solar dried mango ... more Descriptive sensory characteristics, consumer liking and preference mapping of solar dried mango cv Dodo wereinvestigated in this study . Three solar drying methods solar cabinet direct dryer (CDD), cabinet mixed-mode dryer (CMD) and Tunnel dryer (TD) were used to dry mango samples while fresh sample was used as control. Descriptive sensory analysis was performed by 15 trained panelists who used 6 descriptors to quantitatively describe the sensory characteristics of mango samples while 78 consumers were used to assess the degree of liking of products’ sensory attributes using nine-point hedonic scale. External preference mapping was performed by relating sensory data with hedonic responses. Randomized complete block research design with panelists and samples as main principal factors was used. The results showed significant differences (p<0.05) in mean intensity scores of whiteness, hardness and sweetness attributes with dried samples having higher values than their fresh counterparts. Fresh sample had significantly (p<0.05) higher colour intensity score than dried samples. The consumer study showed that, with exception of taste attribute, consumers showed significant (p<0.05) differences in colour, texture, mouth feel and overall acceptability with fresh samples having higher values than dried counterparts. Moreover, the preference mapping results showed colour and acidity (flavour) attributes to be the main driver for positive consumer preference for fresh samples. Among the drying methods, tunnel dryer showed a relatively close relationship with these attributes than cabinet dryers. In conclusion, solar drying has significant effect on sensory attributes of dried mango especially colour and flavour which is also dependent on the drying method employed. Therefore, selection of appropriate drying method which will retain these attributes is of greater importance for consumer acceptability and marketability. Keywords : Mango, Sensory, Descriptive, Consumer, Preference Mapping

Postgraduate Medical Journal, 1986

A young woman presented with an acute right pontine lesion and paroxysmal atrial fibrillation. Th... more A young woman presented with an acute right pontine lesion and paroxysmal atrial fibrillation. The lesion was later proven by magnetic resonance imaging to be due to multiple sclerosis. To our knowledge, cardiac arrhythmias have not been previously described in this condition. Published support for this possible association is reviewed.

Fertility and Sterility, 2010

into CBSÔ straws and cooled slowly (-0.3 C/min from-7 C to-35 C then plunged). All oocytes were t... more into CBSÔ straws and cooled slowly (-0.3 C/min from-7 C to-35 C then plunged). All oocytes were thawed at room temperature in a series of sucrose dilutions. ICSI was performed on surviving oocytes +2hr postthaw and cultured in LG medium+5%SS (tri-gas, 37 C). Chi squared analysis was performed. RESULTS: 314 Donor oocytes were recovered, 259 cryopreserved (82.5% MII), and 217 thawed, to date. After 25 oocyte thaw cycles, 100% recovery was achieved, with survival and fertilization rates being higher (P<0.05) by mS VTF (87%, 82%) versus SF (45%, 59%). Pregnancy, ongoing/live birth and implantation rates also were higher by mS VTF (64%, 43%, 45%, respectively) than SF (29%, 14%, 13%, respectively). CONCLUSION: mS VTF in S3-Oocyte solutions proved to be a more reliable technique than SF in CJ3 solutions for oocyte cryopreservation. Some variation in oocyte survival and embryo development seen in the mS VTF treatment is likely attributed to differences in cytoplasmic maturation/egg quality between donor sources.

African Journal of Food Science, May 27, 2015

The effects of solar drying methods [Cabinet direct (CDD), cabinet mixed mode (CMD) and tunnel (T... more The effects of solar drying methods [Cabinet direct (CDD), cabinet mixed mode (CMD) and tunnel (TD) drying] on total phenolic content (TPC) and antioxidant capacities of commonly consumed fruits and vegetable in Tanzania were investigated. The TPC and FRAP in mangoes (Mangifera indica cv. Dodo, Viringe and Kent), bananas (Musa acuminata, cv. Kisukari, Kimalindi and Mtwike), pineapples (Ananas comosuss cv Smooth cayenne) and tomatoes (Lycopersicum esculentum cv. Tanya, Cal J and Onyx) were evaluated using Folin-Ciocalteu reagent and ferric reducing antioxidant power (FRAP) methods, respectively. There were significant (p<0.05) variations in TPC (mg GAE/100 g DM) and FRAP (µmol/100 g DM) among the fresh fruit and vegetable samples. The highest TPC was in tomato (476.6±8.6-538.9± 1.4) and lowest in banana (139.3±2.3-189.2±2.7). Drying methods had significant (p<0.05) effect on TPC and antioxidant values of the samples. All fresh samples had higher TPC levels but declined significantly in dried samples with the exception of tunnel dried tomatoes. Among the dried samples, the tunnel dried samples had less TPC loss (6-16%) than the cabinet dried samples (17-42%). The cabinet direct and mixed mode samples were not statistically different (p>0.05) from each other. However, tunnel dried samples had less FRAP loss (6-13%) which were statistically different (p<0.05) from the cabinet dried samples (14-56%). Percentage TPC and FRAP recoveries (%) differed significantly (P<0.05) between the varieties within the fruits/vegetable for both drying methods. A strong correlations between TPC and FRAP in both fresh (R 2 = 0.970) and dried samples (R 2 =0.8636) suggests that solar drying methods have significant effects on total phenolic contents and antioxidant activities of fruits and vegetables with tunnel drying method giving significantly less effects.

Total phenolic compounds (TPC), total flavonoid contents (TFC) and antioxidant activity of extrac... more Total phenolic compounds (TPC), total flavonoid contents (TFC) and antioxidant activity of extracts from 8 varieties of Chinese and Thai rice grains were evaluated. Extraction was done using water (at 25°C), hot water (at 50°C) and 70% ethanol. Highest TPC and TFC were seen in all rice varieties after extraction with 70% ethanol. The Heimi variety of Chinese rice showed the highest TPC and TFC (634.83 and 158.47 mg/kg, respectively) followed by Jing Nian variety, also from China, Dok Kam and Niaow Deang varieties both from Thailand, respectively. Highest antioxidant activity was observed in Heimi followed by Jing Nian, Dok Kam and Niaow Deang varieties. The color of Heimi and Jing Nian is black, and that for Dok Kam and Niaow Deang is red, so TPC and TFC were correlated with the color of rice. However, no correlation was observed with the Nang Dum variety from Thailand even though it has a black color. Its TPC and TFC were found to be statistically the same as that of the white-colored Ji Nong Da, T-You 597 and Xiang Wan Nuo 1 Hao varieties from China. Antioxidant activities from each solvent system extraction (water, hot water and 70% ethanol) were also found to be directly correlated with the quantity of TPC and TFC. The TPC had positive correlations with DPPH scavenging (R 2 = 0.9155, 0.9358 and 0.9625), reducing power (R 2 = 0.9799, 0.8521 and 0.9733) and inhibition of lipid peroxidation (R 2 = 0.7621, 0.7429 and 0.9610). TFC also had positive correlations with DPPH scavenging (R 2 = 0.9098, 0.9246 and 0.9477), reducing power (R 2 = 0.9916, 0.9745 and 0.9844) and inhibition of lipid peroxidation (R 2 = 0.7548, 0.7178 and 0.8283), respectively.

Tanzania Journal of Science

Jackfruit seeds flour is very rich in nutrients and may be incorporated into wheat flour to devel... more Jackfruit seeds flour is very rich in nutrients and may be incorporated into wheat flour to develop nutrient dense baked products. Consumption of these products may improve the nutrition status of the people, hence fulfill sustainable development goal number two. In this study, nutritional composition, sensory profile, and consumer acceptability of wheat-jackfruit seeds composite buns (Mandazi) were investigated. Jackfruit seeds flour (JSF) was developed and incorporated into wheat flour (WF) at 10, 20, and 30% to produce composite flour used for bun preparation. Flours and buns were subjected to proximate, mineral, and sensory analyses with WF serving as a control sample. JSF had significantly (p < 0.05) higher protein, fibre and mineral contents than wheat flour. Proximate and mineral contents increased significantly (p < 0.05) in bun samples with increasing levels of WF substitution in the formulations. As for sensory analysis, whole wheat control buns and 10% composite bun...

Journal of Food Processing and Preservation