Department of Food Process Engineering
Permanent URI for this collectionhttp://197.255.125.131:4000/handle/123456789/4855
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Item Fabrication And Characterization Of Crosslinked Cellulose Nanocrystals Re-Enforced Bipolymeric Films For Preservation Of Leafy Vegetables(University Of Ghana, 2021-07) Lartey, C.S.N.L.Biodegradable polymer films are increasingly being used as alternate packaging material due to the less environmental and health burden compared to synthetic plastics. Biobased films are also attractive candidates for packaging fresh food such as vegetables and fruits as they possess high moisture retention capacity and maintain desirable sufficient moist surface around the fresh food. Due to the high hydrophilicity of biobased or biodegradable polymers, the practical application of biobased polymer films in food packaging is challenging as their large hydrophilic groups on surface and in between polymer chains can absorb excess moisture which may lead to polymer chain disentanglement and dissolution as excess water can disrupt the weak physical forces (intermolecular hydrogen bonding) holding the individual polymer chains together in the film. The objective of the work is to perform film post treatment techniques in reducing the number of free hydrophilic groups on the surface of the film as well as dehydrate the film using chemical crosslinking and thermal treatment respectively. In this work, a simple packaging film was fabricated by solution casting method using polyvinyl alcohol (PVA), chitosan, citric acid as cross linker and cellulose nanocrystals (CNC) in varied amounts, as fillers to enhance mechanical strength. The films were characterized using tensile machine, Fourier Transformed Infra-red spectroscopy, thermal analysis, moisture absorption studies, film dissolution, film permeability studies and X-ray diffraction analysis. Varying the amount of CNC affected the thermal stability of the films, wherein increased amounts improved thermal properties. TGA studies showed that T max (temperature where highest mass loss occurs) in E3 (398°C) increased to 404 °C in E12 with increased amounts of CNC. Acylation with acetic anhydride, heat treatment of films at 100°C and a combination of both treatments improved film stability in water. Swelling degree observed after 15 minutes of immersion of films in distilled water were at their barest minimum in all films subjected to any of the treatments. The films significantly decreased the rate of browning of fresh lettuce, keeping its fresh green colour for approximately eleven days before signs of browning set in. This was in contrast to fresh lettuce packaged with poly ethylene films which turn brown after three to four days. The fabricated films may serve as active packaging system for extending the shelf life of fresh lettuce, and potentially other vegetables and fruits in the food distribution chain.Item Noni Juice Extraction: Process Evaluation and Design for Efficiency(University Of Ghana, 2020-10) Nartey, N.A study examined factors affecting the time of drip extraction of noni (Morinda citrifolia) juice. The factors studied were the presence of noni fruit peels, temperature of extraction, extraction time, water addition during extraction and the quantity of fruits used for extraction. Morinda citrifolia juice was dripped extracted from the noni fruit to determine the influence of temperature, time and mass of fruit on the drip extraction process separately before combining these factors to design a CCRD experiment. The effect of each factor was assessed with a factorial experiment followed with analysis of variance. Temperature and mass of fruit extracted were found to affect the time of drip extraction and the quality of juice produced in terms of yield and physio-chemical characteristics of the juice of which pH and total soluble solids were considered. Using the CCRD, different combinations of fruit mass (0.5, 0.8, 1.25, 1.7 and 2 kg), temperature of extraction (30, 36.08, 45, 53.92 and 60oC) and extraction time (3, 6.65, 12, 17.35 and 21days) were used to drip juice from the noni fruit. Total soluble solids content, pH and juice recovered in terms of yield were measured after each extraction. CCRD results showed that the responses of pH, total soluble solids and yield were in good agreement with the theoretically predicted values of the model. Total soluble solids content and pH were significantly affected by temperature of extraction and the extraction duration (time) whiles noni juice yield was significantly affected by the mass of fruit drip extracted.Item Design and Fabrication of a Control System for a Photovoltaic-Greenhouse Solar Dryer and Performance Evaluation of the Dryer(University of Ghana, 2019-07) Afenyie-Abekah, M.Solar dryers have become important components for the delivery of dried agricultural products of high quality. They generally are designed to maximize the production of a heating system based on solar radiation. This study involved the design, building and testing of a control system to allow the monitoring of temperature, solar radiations and control of humidity in a Photovoltaic (PV)-Greenhouse Solar Dryer (PVGSD). This was accomplished by assembling a solar charge controller, three solar panels, a power inverter, and a battery system. An Arduino UNO Rev3, DHT22-sensor, solderless breadboard, Liquid Crystal Display (LCD) screen, jumper cables, Light-Emitting Diode (LED) red, Global System for Mobile (GSM) communication module, 10k Ω, 220 Ω and 1k Ω resistors and two 5V one channel relays formed the control system. These were assembled in a multi-functional workstation linked to the solar dryer. The GSM communication module was an innovation to allow connection to the internet over General Packet Radio Service (GPRS) network and send/receive SMS. It was used to control the fans remotely and further allowed logging of periodic sensor data (temperature, humidity, voltage and solar radiation values) by sending SMS to a phone number and server. Dryer and product characteristics were measured including temperature, humidity, solar radiation and moisture content. The temperature and humidity profile were monitored for 11 days in the empty PVGSD without the workstation and Open Sun Drying (OSD) showed that the PVGSD recorded the highest temperature of 69oC occurring between 12:00 and 14:00 hours GMT while the OSD recorded at 41.5oC. The highest relative humidity recorded in the PVGSD was 75.5% and 83% for OSD observed at night from 20:00 hours to 5:00 hours GMT. Two commodities, cassava (slices and chunks) and red pepper were dried to evaluate the dryer efficiency, and this was compared with OSD and existing greenhouse type solar dryer (GSD). The cassava slices dried faster than the cassava chunks in all the drying methods indicating that sample size influenced drying rate. PVGSD had a faster drying rate for cassava slices of 0.0732g/g.h compared to 0.04908g/g.h for GSD and 0.02074g/g.h for OSD, while drying rate of PVGSD, GSD and OSD for cassava chunks were 0.0457g/g.h, 0.0355g/g.h and 0.01667g/g.h respectively. Similarly, PVGSD was observed to obtain the highest rate of drying for red pepper of 0.097g/g.h compared to GSD of 0.094g/g.h and OSD of 0.047g/g.h. The drying method, time and sample size were found to have statistical significance (p<0.05) on temperature, moisture content, humidity and drying rate. The PVGSD dryer with the workstation was able to keep the humidity conditions in the dryer low to prevent moisture uptake during the night. The samples in this dryer showed consistent drop in moisture content throughout the drying period. To further evaluate the drying effect on the samples, laboratory analyses such as water activity, color profile and particle size determination were performed on the resultant dried cassava flour samples and red pepper (whole). The color profile of red pepper flour and cassava flour from the PVGSD was observed to be better in terms of the redness (a*) for red pepper, lightness (L*) for cassava, browning index (BI) and color change (ΔE). The color change of red pepper for PVGSD, GSD and OSD were 11.94, 16.43 and 25.25 respectively. The color change of cassava slices for PVGSD, GSD and OSD were 10.49, 10.84 and 11.59 respectively, while that for cassava chunks recorded at 10.60, 12.09 and 12.11 respectively for PVGSD, GSD and OSD. The SD50 values for flours from the slices were finer than those from the chunks. The SD50 values for cassava slices under PVGSD, GSD and OSD were 62 μm, 76 μm and 78 μm respectively, while SD50 values for cassava chunks under PVGSD, GSD and OSD recorded at 80 μm, 92 μm and 106 μm respectively. In general, cassava slices under the three drying methods demonstrated a better quality than the chunks in terms of color and particle size. All samples were dried to a water activity below 0.500 to prevent microbial spoilage. Final water activity for red pepper was 0.384, 0.388 and 0.414 respectively for PVGSD, GSD and OSD, while that for cassava slices and chunk for PVGSD was 0.361 and 0.415 respectively, GSD was 0.384 and 0.446 respectively and OSD recorded at 0.421 and 0.490 respectively. To further understand and describe the drying curves for the samples under the three drying methods, 12 Thin Layer Mathematical models were evaluated. The best model under this study for red pepper is the Midilli and Kucuk model under both PVGSD and GSD while Logarithmic model describes best under OSD. Approximation of diffusion model can be used for cassava slices under PVGSD and GSD, while Midilli and Kucuk model for OSD. These models were selected according to the lowest Root Mean Square Error (RMSE) and chi square (χ2) and highest correlation coefficient (R2).