The use of near ambient air drying for the preservation of wheat stored in granaries is common in Western Canada. Guidelines have been developed to assist farmers in selecting appropriate drying methods. During this process the top layer of wheat can remain at moisture contents (m.c.) greater than the safe storage limit, 14.5% wet bulb (wb), for up to 12 weeks. This study tested the effects of this drying procedure on the development of ochratoxin A (OTA) using 1 m3 bulks of durum wheat at 18% m.c. (wb) contained within steel bins inside a Weather Simulation Lab. In a second study using 20 L volumes of wheat at a m.c. of 20% (wb) within an environmental growth chamber potential development of OTA was also evaluated. The wheat was exposed to two treatments, airflow and no airflow, for a period of 12 weeks under conditions of high relative humidity (greater than 80%) and typical Manitoba fall temperatures. The storage quality parameters of germination, fat acidity value, and presence of OTA were measured weekly. It was found that high moisture wheat stored under all treatment conditions showed a rapid decrease in germination and increase in fat acidity value over time, with no significant difference between the treatments. Under the tested conditions the development of ochratoxin A was not detected in significant quantities in the 1 m3 bulks of grain but was detected in the smaller 20 L bulks.

The use of near ambient air drying for the preservation of wheat stored in granaries is common in Western Canada. Guidelines have been developed to assist farmers in selecting appropriate drying methods. During this process the top layer of wheat can remain at moisture contents (m.c.) greater than the safe storage limit, 14.5% wet bulb (wb), for up to 12 weeks. This study tested the effects of this drying procedure on the development of ochratoxin A (OTA) using 1 m3 bulks of durum wheat at 18% m.c. (wb) contained within steel bins inside a Weather Simulation Lab. In a second study using 20 L volumes of wheat at a m.c. of 20% (wb) within an environmental growth chamber potential development of OTA was also evaluated. The wheat was exposed to two treatments, airflow and no airflow, for a period of 12 weeks under conditions of high relative humidity (greater than 80%) and typical Manitoba fall temperatures. The storage quality parameters of germination, fat acidity value, and presence of OTA were measured weekly. It was found that high moisture wheat stored under all treatment conditions showed a rapid decrease in germination and increase in fat acidity value over time, with no significant difference between the treatments. Under the tested conditions the development of ochratoxin A was not detected in significant quantities in the 1 m3 bulks of grain but was detected in the smaller 20 L bulks.

Neste trabalho, estudou-se o impacto de dois pré-tratamentos: ultrassom, pulso de vácuo e a combinação de ultrassom seguido de pulso de vácuo, sobre a cinética de secagem da banana verde a (50 e 60) °C. Na secagem a 50 °C constatou-se que, a aplicação de uma única técnica foi mais favorável que a combinação dos pré-tratamentos (20 min de ultrassom, seguido de 60 min de pulso de vácuo), sendo que os melhores resultados foram obtidos com 20 min de ultrassom na potência volumétrica ultrassônica de (9,38 ± 0,60) W/L. Os valores da difusividade efetiva da água, da primeira e segunda fases de taxa decrecente foram de (7,03 ± 0,09 e 3,84 ± 0,09) × 10-9 m2/s para (12,10 ± 0,47 e 6,84 ± 0,28) × 10-9 m2/s, respectivamente, com a aplicação do ultrassom por 20 min. Na secagem a 60 °C, para a primeira fase de taxa decrescente, o pré-tratamento de 25 min de ultrassom resultou mais favorável. Já para a segunda fase de taxa decrescente o pré-tratamento com 25 min de ultrassom e a técnica combinada (25 min de ultrassom, seguido de 60 min de pulso de vácuo) foram os mais eficientes. Desta forma, a hipótese inicial de que micro-canais gerados pelo ultrassom e o gradiente de pressão nos pulsos de vácuo promoveriam maior migração de umidade não foi comprovada. A 60 °C, o aumento dos valores de difusividade efetiva de água, em relação aos ensaios sem prétratamento, foram menores se comparados aos aumentos obtidos nos ensaios a 50 °C. Consequentemente, a 60 °C, o efeito da temperatura prevaleceu, e os efeitos causados pelos pré-tratamentos foram menos evidentes em relação aos ensaios a 50 °C. O modelo de Midilli resultou no melhor modelo para o ajuste dos dados experimentais de secagem com r2>=0,999, RMSE<=0,0119 e ?2<=0,00012. O processo aplicando 20 min de ultrassom na potência volumétrica ultrassônica de (9,38 ± 0,60) W/L e temperatura de secagem de 50 °C diminuiu 30 min o tempo de secagem. A economia do custo de energia sob essas condição iria de (1,12 para 1,05) R$/kg de matéria-prima processada. Embora, uma redução da quantidade de energia necessária para a gelatinização foi observada, devido a aplicação do ultrassom por 20 min e secagem a 50 °C, não foi observada redução significativa do teor de amido resistente, assim, a principal característica da farinha de banana verde, por causa de seu efeito positivo sobre a saúde humana, foi preservada. Constatou-se que, aplicação de 20 min de ultrassom (9,38 ± 0,60) W/L em rodelas imersas em água (hidratadas) ou embaladas a vácuo (não hidratadas) não influenciou significativamente os valores de difusividade efetiva da água, o conteúdo de AR, nem a formação dos micro-canais. Os efeitos do ultrassom foram evidentes independentemente do ganho de água, acontecido devido à imersão das rodelas de banana verde em água. / In this work, the impact of two pre-treatments: ultrasound, pulsed-vacuum and the combination of ultrasound followed by pulsed-vacuum, on the drying kinetics of unripe banana at (50 and 60) ° C were studied. For air-drying at 50 °C, the application of a single technique was more favorable for water migration than the combination of pre-treatments (20 min of ultrasound, followed by 60 min of pulsed-vacuum); the best results were observed with ultrasound for 20 min at ultrasonic volumetric power of (9.38 ± 0.60) W/L. For this condition, the values of effective water diffusivity for the first and second phases of decreasing rate were (7.03 ± 0.09 and 3.84 ± 0.09) × 10-9 m2/s to (12.10 ± 0.47 and 6.84 ± 0.28) × 10-9 m2/s, respectively. At 60 °C, for the first phase of decreasing rate, 25 min of ultrasound resulted more favorable, whereas, for the second phase of decreasing rate, ultrasound for 25 min and the combined technique (25 min ultrasound, followed by 60 min pulsed-vacuum) resulted favorable. Thus, the initial hypothesis that micro-channels from ultrasound pre-treatment and pressure gradient from pulsed-vacuum pre-treatment would help moisture migration was not observed. At 60 °C, the increase of the values of effective water diffusivity were lower than those obtained at 50 °C. Consequently, at 60 °C, the effect of temperature prevailed, and the effects caused by pretreatments were less evident with respect to the assays at 50 °C. The Midilli model was the best model for adjusting the experimental drying data with r2>=0.999, RMSE<= 0.0119 and x2<=0.00012. The process applying 20 min of ultrasound at ultrasonic volumetric power of (9.38 ± 0.60) W/L and air-drying at 50 °C saved 30 min of air-drying time. The economy of energy cost under these conditions would represent a value from (1.12 to 1.05) R$/kg of processed raw material. Although a reduction in the amount of energy required for gelatinization was observed due to the application of ultrasound for 20 min and air-drying temperature at 50 °C, no significant reduction of resistant starch content was observed; thus, the main characteristic of unripe banana flour, because of its positive effect on human health, was preserved. It was verified that the application of 20 min of ultrasound (9.38 ± 0.60) W/L in unripe banana slices, immersed in water (hydrated) or vacuum-packed (non-hydrated), did not influence significantly the values of effective water diffusivity, resistant starch content and the formation of micro-channels. The effects of ultrasound were evident independent of water gain, which occurs due to the immersion of unripe banana slices into water.

The use of volatile organic compounds (VOC) in coating materials has adverse effects on both human health and the environment. Due to concern over these problems, coating industry has attempted to decrease the solvent contents of coating materials for the last three decades by developing water dispersed and powder paints. A recently developed method to make solvent free paint is to use highly branched polymers in high solid alkyd resins. Highly branched polymers help to achieve resins with viscosity much lower than its linear counterparts. In this study, a new alkyd based resin was formulated using long oil alkyd and melamine based hyperbranched polymer having 24 functional groups on its structure. The long oil alkyd was synthesized by using an oil mixture (40% linseed + 60% sunflower). Melamine was preferred as core molecule due to its excellent properties such as greater hardness, alkali and solvent resistance with thermal stability. The resin produced has low viscosity because its hyperbranched structure / therefore, it needs no solvent for its application. The chemical characterization of the resins with different compositions was performed using Fourier Transform Infrared Spectroscopy and thermal properties were determined by Differential Scanning Calorimetry. Physical and mechanical tests were conducted to determine hardness, flexibility, impact resistance, abrasion resistance, adhesion power, and gloss property of the samples. The viscosity of the resins decreased from 148 Pa.s to 8.84 Pa.s as the hyperbranched polymer to long oil alkyd ratio was increased from 1:3 to 1:24. On the other hand, the hardness values of the resins decreased from 198 Persoz to 43 Persoz. All resins showed excellent flexibility, formability, adhesion, and gloss.

There has been a considerable effort in the last years to decrease the amount of volatile organic compounds (VOCs) present in organic coatings. The risks to human health and environmental hazards associated with VOCs, governmental directives, and economic factors are the main driving forces behind this effort. One way of achieving less or no VOC containing coating systems is to produce low viscosity resins. Hyperbranched resins owing to their globular structure have low viscosities and are promising materials for decreasing the VOCs. In this research hyperbranched resins having properties close to alkyds were synthesized. Dipentaerythritol, which was used as the core was esterified with dimethylol propionic acid. The hyperbranched polyester was then esterified with the castor oil fatty acids (Castor FA). The hydroxyl group of the ricinoleic acid present in the castor FA was modified with different amounts of linseed oil fatty acids (Linseed FA) and benzoic acid. The chemical characterization of the resins was achieved by FTIR spectroscopy and the thermal properties were determined by DSC. Then, the physical and the mechanical tests were carried out. The resins containing the Castor FA only and 32.5 % Linseed FA in addition to the Castor FA had 24 and 68 Persoz hardness, respectively. The viscosity of the resins decreased from 17.3 Pa&amp / #61655 / s to 5.8 Pa&amp / #61655 / s as the amount of the Linseed FA was increased. The resins showed excellent adhesion, gloss, flexibility and formability.

In this research hyperbranched resins containing fatty acid residues like alkyds were synthesized. Dipentaerythritol which has six hydroxyl groups was used as the core molecule, and it was transesterified with (i) castor oil, and (ii) a mixture of castor oil and linseed oil at 240&deg / C in the presence of sodium hydroxide as catalyst. The resulting molecule, in either case, was then esterified with dimethylol propionic acid at 140&deg / C in the presence of p-toluene sulfonic acid as catalyst. Melamine-formaldehyde resin was synthesized to be used with the synthesized hyperbranched resins, and it was successfully modified by all hyperbranched resins at a ratio of 3:1. FTIR spectroscopy was used to characterize the hyperbranched resins and the thermal properties were determined by DSC. DSC showed that the hyperbranched resins decomposed between 315-345&deg / C. The viscosity of the resin that was synthesized by using only castor oil was 3.0 Pa.s and by using 50% linseed oil it was 1.0 Pa.s. When reacted with dimethylol propionic acid, the former&rsquo / s viscosity increased to 7.0 Pa.s, and the second&rsquo / s viscosity increased to 3.7 Pa.s. The hyperbranched resins showed excellent adhesion, gloss, flexibility, and formability. The mixture of hyperbranched resin plus melamine-formaldehyde resin samples had higher hardness values but lower gloss, adhesion and bending resistance values than the hyperbranched resins, and they had good impact and abrasion resistances.

Neste trabalho, estudou-se o impacto de dois pré-tratamentos: ultrassom, pulso de vácuo e a combinação de ultrassom seguido de pulso de vácuo, sobre a cinética de secagem da banana verde a (50 e 60) °C. Na secagem a 50 °C constatou-se que, a aplicação de uma única técnica foi mais favorável que a combinação dos pré-tratamentos (20 min de ultrassom, seguido de 60 min de pulso de vácuo), sendo que os melhores resultados foram obtidos com 20 min de ultrassom na potência volumétrica ultrassônica de (9,38 ± 0,60) W/L. Os valores da difusividade efetiva da água, da primeira e segunda fases de taxa decrecente foram de (7,03 ± 0,09 e 3,84 ± 0,09) × 10-9 m2/s para (12,10 ± 0,47 e 6,84 ± 0,28) × 10-9 m2/s, respectivamente, com a aplicação do ultrassom por 20 min. Na secagem a 60 °C, para a primeira fase de taxa decrescente, o pré-tratamento de 25 min de ultrassom resultou mais favorável. Já para a segunda fase de taxa decrescente o pré-tratamento com 25 min de ultrassom e a técnica combinada (25 min de ultrassom, seguido de 60 min de pulso de vácuo) foram os mais eficientes. Desta forma, a hipótese inicial de que micro-canais gerados pelo ultrassom e o gradiente de pressão nos pulsos de vácuo promoveriam maior migração de umidade não foi comprovada. A 60 °C, o aumento dos valores de difusividade efetiva de água, em relação aos ensaios sem prétratamento, foram menores se comparados aos aumentos obtidos nos ensaios a 50 °C. Consequentemente, a 60 °C, o efeito da temperatura prevaleceu, e os efeitos causados pelos pré-tratamentos foram menos evidentes em relação aos ensaios a 50 °C. O modelo de Midilli resultou no melhor modelo para o ajuste dos dados experimentais de secagem com r2>=0,999, RMSE<=0,0119 e ?2<=0,00012. O processo aplicando 20 min de ultrassom na potência volumétrica ultrassônica de (9,38 ± 0,60) W/L e temperatura de secagem de 50 °C diminuiu 30 min o tempo de secagem. A economia do custo de energia sob essas condição iria de (1,12 para 1,05) R$/kg de matéria-prima processada. Embora, uma redução da quantidade de energia necessária para a gelatinização foi observada, devido a aplicação do ultrassom por 20 min e secagem a 50 °C, não foi observada redução significativa do teor de amido resistente, assim, a principal característica da farinha de banana verde, por causa de seu efeito positivo sobre a saúde humana, foi preservada. Constatou-se que, aplicação de 20 min de ultrassom (9,38 ± 0,60) W/L em rodelas imersas em água (hidratadas) ou embaladas a vácuo (não hidratadas) não influenciou significativamente os valores de difusividade efetiva da água, o conteúdo de AR, nem a formação dos micro-canais. Os efeitos do ultrassom foram evidentes independentemente do ganho de água, acontecido devido à imersão das rodelas de banana verde em água. / In this work, the impact of two pre-treatments: ultrasound, pulsed-vacuum and the combination of ultrasound followed by pulsed-vacuum, on the drying kinetics of unripe banana at (50 and 60) ° C were studied. For air-drying at 50 °C, the application of a single technique was more favorable for water migration than the combination of pre-treatments (20 min of ultrasound, followed by 60 min of pulsed-vacuum); the best results were observed with ultrasound for 20 min at ultrasonic volumetric power of (9.38 ± 0.60) W/L. For this condition, the values of effective water diffusivity for the first and second phases of decreasing rate were (7.03 ± 0.09 and 3.84 ± 0.09) × 10-9 m2/s to (12.10 ± 0.47 and 6.84 ± 0.28) × 10-9 m2/s, respectively. At 60 °C, for the first phase of decreasing rate, 25 min of ultrasound resulted more favorable, whereas, for the second phase of decreasing rate, ultrasound for 25 min and the combined technique (25 min ultrasound, followed by 60 min pulsed-vacuum) resulted favorable. Thus, the initial hypothesis that micro-channels from ultrasound pre-treatment and pressure gradient from pulsed-vacuum pre-treatment would help moisture migration was not observed. At 60 °C, the increase of the values of effective water diffusivity were lower than those obtained at 50 °C. Consequently, at 60 °C, the effect of temperature prevailed, and the effects caused by pretreatments were less evident with respect to the assays at 50 °C. The Midilli model was the best model for adjusting the experimental drying data with r2>=0.999, RMSE<= 0.0119 and x2<=0.00012. The process applying 20 min of ultrasound at ultrasonic volumetric power of (9.38 ± 0.60) W/L and air-drying at 50 °C saved 30 min of air-drying time. The economy of energy cost under these conditions would represent a value from (1.12 to 1.05) R$/kg of processed raw material. Although a reduction in the amount of energy required for gelatinization was observed due to the application of ultrasound for 20 min and air-drying temperature at 50 °C, no significant reduction of resistant starch content was observed; thus, the main characteristic of unripe banana flour, because of its positive effect on human health, was preserved. It was verified that the application of 20 min of ultrasound (9.38 ± 0.60) W/L in unripe banana slices, immersed in water (hydrated) or vacuum-packed (non-hydrated), did not influence significantly the values of effective water diffusivity, resistant starch content and the formation of micro-channels. The effects of ultrasound were evident independent of water gain, which occurs due to the immersion of unripe banana slices into water.

Thesis (M. Sc. (Agriculture)) --University of Limpopo, 2017 / Tea is one of the most popular consumed beverages in the world, which has beneficial properties such as anti-oxidization, anti-carcinoma and preventing arteriosclerosis. The major essential components of catechins present in tea leaves, includes epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), epicatechin (EC), gallocatechin (GC) and catechin (C). Influence of time-based hot air drying method on chemical composition of the Jatropha zeyheri Sond, widely consumed in rural communities of Zebediela (Khureng village), Limpopo Province, South Africa, was investigated. Four treatments, namely; 0, 24, 48, and 72 hours, were arranged in completely randomised design (CRD), replicated five times. The study demonstrated that drying significantly increased total phenolic content, total antioxidant capacity and tannin content. It also demonstrated that drying significantly increased minerals elements; Mg, K, P, S, Al, Co, Mn, Si and Zn content and decreased Na, Ca and Ni and Zn quantities. Sodium-potassium ratio was very low across drying periods. Drying time did not significantly influence proximate chemicals; energy, protein, carbohydrates, ash and fibre content. Moisture and fat were significantly increased by drying period. Results of the study suggested that time-based hot air drying method improved the chemical composition of J. zeyheri, which has the potential of enhancing nutrition in marginal rural communities of Limpopo Province.

The objectives of this project were:<br />1.����To compare the drying cost and drying time for oak and poplar pallets for the following mold mitigation strategies for hardwood pallets: air drying, forced air drying (fan shed), kiln drying to 25% moisture content and chemical treatment, and<br />2.����Develop and evaluate a procedure for preventing and controlling mold growth on heat treated hardwood pallets<br />Twenty red oak pallets and twenty yellow-poplar pallets were tested for each drying method to compare costs and to determine drying times. �Additional pallets were obtained to conduct a more thorough air drying procedure. �Drying data was extrapolated to allow estimates of the drying time from green (83% moisture content for poplar and 64% moisture content for oak) to 25%. �<br />After the pallets reached the desired 25% moisture content, they were placed in a 40�" enclosed trailer, inoculated with mold (Aspergillus, Stachybotrys, and Penicillium) and were left undisturbed for a period of 14 days. �After the 14 day incubation period, the pallets were inspected for mold using the ASTM D-4445 Standard Test Method for Fungicides for Controlling Sapstain and Mold on Unseasoned Lumber. �<br />A comparison of drying costs was then conducted to determine which method was the most cost efficient based on the data obtained in this study. �The cost to treat the pallets with each treatment was calculated including electrical cost, labor, and tax values. �In addition to the cost comparison, a Net Present Value (NPV) was calculated to determine which method produced the best outcome over a longer period of time.<br />Two heat treatment and drying schedules were then developed to meet both IPPC-ISPM #15 requirements and achieve the desired 25% moisture content with minimal degrade. �This was accomplished by testing several HT/drying schedules on green yellow-poplar and white oak pallets until the pallets met the criteria for being heat treated and had minimal degrade. �The schedules developed are a modified oak HT/KD schedule that required 30 hours to complete and a modified poplar HT/KD schedule that required 16 hours to complete.<br />The results demonstrated that that mold would not grow on the pallets stored in an enclosed container when the dew point is not reached. Air-drying pallets, chemical application in conjunction with air-drying pallets, fan shed drying pallets and kiln drying pallets to a 19-24% moisture content was demonstrated to prevent mold growth on oak and yellow poplar pallets. Estimates for the time required to dry yellow-poplar and oak pallets to 19% and 25% moisture content were developed for air-drying, forced air-drying and kiln drying for the conditions experienced in Blacksburg, VA between 7/30/2008 and 11/10/2008. Air-drying pallets was found to have the lowest daily operational cost but not the lowest total drying cost. �Fan shed drying had the lowest drying cost to achieve 25% moisture content. �Kiln drying was the most expensive daily and total cost, but yielded the fastest method of drying pallets to 25% moisture content. A NPV cost comparison showed that over a 3 year (36 month) time period, fan shed drying is the most cost effective method of drying pallets based on the values used in this study. Given the environmental conditions experienced between 7/30/2008 and 11/10/2008, no mold grew on the air-dried, fan shed, and kiln dried pallets during the drying process. <br /> / Master of Science

Microbial biosensor systems (MBS) are useful for analyte detection owing to their low cost, sensitivity, and selectivity for bioavailable analytes. Due to typically poor shelf-life and sensitivity to external conditions, there are few reports of MBS technology applied to simple analytical devices. The effectiveness of air-drying MBS in natural polymers was investigated as a novel preservation technique. Two colorimetric Escherichia coli MBS, a tetracycline-inducible reporter and an arsenate-inducible reporter, were dried on various substrates yielding novel MBS platforms. In proof-of-concept experiments performed in 96-well microplates, both systems demonstrated responsivity after air-drying in low concentrations of pullulan. However, the MBS were unresponsive following brief storage of 1 week. To improve the preservation of MBS, sensing strips were created by air-drying concentrated acacia gum-based MBS suspensions onto paper. Cells dried on these strips demonstrated responsivity upon solubilization in various tube-based assays. MBS sensing strip responsivity was demonstrated following storage for 6 weeks at 4 °C. Tetracycline-responsive sensing strips also performed well in assays using spiked lake water samples. Air-drying in natural polymers was an effective MBS preservation technique, and allowed for the creation of “mix and read” style assays which were simple, equipment-free and ready-to-use. / Thesis / Master of Science (MSc)