Yam is one of the preferred staple foods in West Africa. The annual vegetative cycle of yam necessitates a long period of storage to make it available all year round. The major problems in yam tuber storage are sprouting, respiration and transpiration, which cause weight and quality losses. In this work, the effects of storage conditions and storage period on the nutritional and other qualities of stored yam tubers were investigated. Storage conditions used were two traditional yam barns, one with fan to aid air circulation and the other without. A total of 216 tubers of yam (Dioscorea roundata) "Giwa" variety with 108 tubers in each barn, were stored in the barns. Parameters evaluated were temperature and relative humidity of the storage environment, signs of deterioration of the tuber such as sprouting, weight loss and rotting and some nutritional parameters (carbohydrate, calcium, phosphorus, crude fibre, crude fat, crude protein, ash and moisture contents). Temperature and relative humidity were measured three times a week and four times a day at 0800h, 1200h, 1600h and 2000h. The results showed that average temperature and relative humidity in the barn with fan were slightly lower than that of the barn without fan. These differences were statistically significant for April, May and June at P< 0.1. Tubers stored in the barn with fan had the least sprout weight and least weight loss. At the end of a 3-month period, the tubers in the ventilated barn showed 4.7% less weight loss compared to the barn without fan. The difference in sprout weights and weight loss between the structures was statistically significant at P≤ 0.05. Also, tubers stored in the barn with fan had the least percentage of rotten tubers (1.85% of stored tubers) compared to the tubers stored in the barn without fan (12.03%). A reduction of some of the nutritional content was also observed during the six months of storage period. From these results it can be concluded that intermittent air flow on stored yam tubers reduces sprouting, weight loss and rot development, thus reducing the overall loss in stored yam tuber. However, moisture, crude protein, carbohydrates, phosphorus and calcium contents of the tuber reduced significantly in the two barns studied.

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Biodegradable nanocomposite films are novel materials for food packaging because of their potential to extend the shelf life of food. In this research, the performance of cassava starch-zincnanocomposite film was evaluated for tomatoes packaging. The films were developed by casting the solutions of 24 g cassava starch, 0-2% (w/w) zinc nanoparticles and 55% (w/w) glycerol in plastic mould of 12 mm depth. The permeability of the films, due to water and oxygen, was investigated at 27°C and 65% relative humidity while the mechanical properties were determined by nanoindentation technique. The average thickness of the dried nanocomposite films was found to be 17±0.13 µm. The performances of films for tomatoes packaging was evaluated in comparison with low density polyethylene (LDPE; 10 µm) at the temperature and period ranges of 10-27°C and 0-9 days, respectively. The quality and microbial attributes of the packaged tomatoes, including ascorbic acid, β-carotene and total coliform were analysed at an interval of 3 days. The results revealed that the water vapour permeability increased while the oxygen permeability decreased with the nanoparticles (P<0.05). The hardness, creep, elastic and plastic works, which determined the plasticity index of the film, decreased generally with the nanoparticles. The films containing 1 and 2% of the nanoparticles suppressed the growth of microorganisms and retained the quality of tomatoes than the LDPE at 27°C and day-9 of packaging (P<0.05). The results implied that the film could effectively be used for tomatoes packaging due to their lower oxygen permeability, hardness, elastic and plastic works.

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A common way of maintaining essential nutrients in fruits and vegetables is through novel food processing techniques such as pretreatment. This study investigated the influence of pretreatment methods on the proximate composition, vitamin C and β-carotene contents of oven dried pawpaw. Fresh, ripe pawpaw fruit were peeled, sliced and pretreated with three pretreatments – ascorbic acid dip (0.45% w/v), honey dip (0.25% v/v) and steam blanching (100 °C). The fruit slices were soaked in ascorbic acid and honey solutions for 4 min while steam blanching was done for 2 min. Untreated pawpaw sample served as the control. The treated and control samples were dried at an average temperature of 65 °C. Results showed that vitamin C of dried pawpaw samples pretreated with honey dip had the highest retention of vitamin C (116.05 mg/100g) compared to ascorbic acid treated (98.90 mg/100g), steam blanched (109.02 mg/100g), and control samples (77.02 mg/100g). In terms of β-carotene, pawpaw sample treated with ascorbic acid solution had the highest value of 12.68 mg/100g. The use of honey and ascorbic acid solutions as treatments prior to drying can improve the retention of nutrients such as vitamin C and β-carotene in dried fruits.Keywords—Pretreatments, proximate properties, vitamin C, β-carotene

A breaker plate of a screw mixer is an efficient mixing device for use in homogenizing nanocomposites. This research was undertaken to investigate the effects of glycerol and diameter of holes in a breaker plate on performance of a screw mixer for nanocomposites. Samples of the nanocomposites were formulated by blending 1000 g cassava starch, 45-55% glycerol and 2% magnetite nanoparticles; and used to evaluate the performance of a locally developed screw mixer at 5 mm and 7 mm diameters of holes in its breaker plate. The effects of glycerol and diameter of holes in the breaker plate on mixing index, amount of unmixed nanocomposites and output/ 1000g were evaluated as performance indices for 1 hour. Empirical models were determined for predicting the performance of the mixer within the designed criteria. The results showed that the output/ 1000g and the mixing index increased with higher glycerol and diameter of holes in the breaker plate. However, the amount of unmixed nanocomposites decreases with a higher diameter of holes in the breaker plate (p<0.05). The maximum output/ 1000g and mixing index lies between 5 mm diameter of holes in the breaker plate and 55% glycerol concentration with an approximate desirability of 0.60. The empirical models developed were fit (R 2 =0.89, p<0.05); and there were no significant differences between actual and predicted values. The results suggest application of 5 mm diameter of holes in the breaker plate for homogenizing nanocomposites for optimum performance.

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Tomato (Solanum lycopersicum L.) is a vegetable crop reported as one of the most popular crops in the world. Producing tomatoes in many developing African countries is plagued with numerous postharvest challenges. Handling and packaging of harvested tomatoes is one of the main challenges faced in Africa. Packaging provides a means of ensuring safe delivery of a product to the ultimate user in a sound condition, at a minimum overall cost. In order to reduce post-harvest losses resulting from packaging and transportation of fresh tomato fruits, an alternative tomato-packaging container using Acrilonitrile-Butadiene-Styrene (ABS) plastic sheet was developed. The drawing was produced using automated computer aided design (AUTO-CAD). The drawing was simulated using 3-dimensional solid works software. The Finite Element Analysis (FEA) was run on the software to determine the tolerable stresses on the base and handles, drop test, buckling test and stack test. Also, design calculations were done for aerodynamics requirement, heat stress, container thickness, packaging ventilations and ergonomics. The container was developed using vacuum forming method from ABS sheet. A compression test was carried out in the strength of materials laboratory. Results revealed that the packaging container can accommodate a maximum load of 0.903 kN, implying that 3 containers when filled with fresh tomato fruits can be stacked on one another. The developed tomato-packaging container is collapsible and easy to maintain by cleaning with water. Ultimately, the tendency of the plastic packaging container to be stacked on top of one another makes it better than the conventional baskets currently used for packaging and transporting fresh tomato fruits.