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Item The impact of heating and drying on protease activities of ruminant milk before and after in vitro infant digestion(Elsevier Ltd, 2023-12-15) Leite JAS; Montoya CA; Loveday SM; Mullaney JA; Loo TS; McNabb WC; Roy NCThis study investigated the effect of heating (63°C/30 min or 75°C/15 s) and drying (spray-drying or freeze-drying) on plasmin, cathepsin D, and elastase activities in bovine, ovine, and caprine milk, compared to non-dried raw milk counterparts. Protease activities and protein hydrolysis were assessed before and after in vitro infant digestion with or without gastric and pancreatic enzymes. At 75°C/15 s, plasmin activity in caprine and ovine milk decreased (69-75%, p<0.05), while cathepsin D activity in spray-dried bovine milk heated increased (2.8-fold, p<0.05). Plasmin and cathepsin D activities increased (<1.2-fold, p<0.05) after in vitro digestion with pancreatin, regardless of milk species. Endogenous milk enzymes hydrolyzed more proteins than gastric enzymes during gastric digestion and contributed to small intestinal digestion. In summary, milk proteases remained active after processing with effects dependent on the species of milk, and they contributed to in vitro protein hydrolysis in the stomach and small intestine.Item Rate controlling mechanisms in atmospheric freeze drying : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemical and Bioprocess Engineering at Massey University, Manawatū, New Zealand(Massey University, 2023) Mathew, MeritAtmospheric freeze drying (AFD) can be considered a cost-effective alternative to vacuum freeze drying (VFD) but the very slow drying rate associated with it limits industrial scale adoption. Nevertheless, there are applications, particularly with thin sections such as sliced fruit or leaves, for which hops is an example, where the rate of AFD is relatively high. Therefore, it is important to understand the rate-controlling mechanisms in AFD and how it is affected by the structure of the fruit or leaf. Such understanding will help identify the bottlenecks of the process and thus the steps that may be taken to overcome them. This project has developed a mathematical model for AFD by considering the intrinsic material properties and the theoretical principles of heat and mass transfer. This could help the end-users to run simulations of AFD for different products and arrive at the best drying strategies to achieve faster drying rates before doing time-consuming and expensive experiments. In this work, hops are considered as the model system for the model development. The study needed high-quality experimental data for continuous in-situ weight loss measurements during AFD and there was a lack of such data in the literature reviewed. To deliver this, part of the project has developed a new experimental apparatus. The experimental apparatus developed is capable of continuous weight-loss measurement and data logging temperature and RH of the air in the drying chamber. Temporal weight-loss trial data are used to fit parameters and predict the drying rate and product weight loss. During the study it was found that AFD of hops is a mass transfer limited process. The drying rate was found to increase with process temperature and the adsorbent to hops ratio. Air circulation also helped in increasing the drying rate. The one-dimensional model developed to simulate AFD of hops was able to predict the drying behaviour based on the process parameters and the fitting factors for the hops. Ice sublimation was also studied in this project, based on the hypothesis that the AFD of hops is a type of pure ice sublimation with an additional layer of resistance to mass transfer. This hypothesis was found to be true for the present case and the model was development based on this.Item Improving the quality of dried Theobroma cacao beans using a solar assisted desiccant-based dryer : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand(Massey University, 2023) Raju, Rupantri Nandika"Theobroma cacao" beans are an economically significant commodity for the Fiji Islands. The cocoa beans are harvested in the wild and then fermented and sun-dried under tropical weather conditions. The high relative humidity (RH) as well as the unpredictable weather conditions extend the sun-drying time and causes quality issues in the final dried product. Maintaining product quality is important as export quality cocoa beans are sold at premium prices to chocolate manufacturers internationally. The problems in sun-dying can be solved by reducing the RH of drying air stream. This is possible with desiccant wheel technology (DWT). The solid desiccant material in DWT desorbs moisture from air and reduces humidity. The desiccant material can be regeneration between 60 and 100 °C for the next cycle. This temperature conditions can be achieved by using a solar dryer. This study tested the drying conditions below 20% RH on small batches (6 kg) of fermented Fijian cocoa beans at 45 °C and 55 °C. Impact of these conditions on the drying kinetics and bioactive quality was tested. Experimental data was used to validate a mechanistic drying model. The model was developed using partial differential equations (PDEs) with an implicit scheme for a targeted drying time of 72 hours. Finite difference method (FDM) was used to solve PDEs. The model output was comparable to experimental data from drying runs in Fiji. Reducing the RH at 45 °C showed a better retention of key bioactive compounds, such as polyphenols, caffeine, and theobromine when compared to other treatments. These findings are presented in detail in this thesis and suggests that DWT can provide consistent drying conditions in a tropical environment. The drying model is a useful tool for predicting the drying conditions for cocoa beans based on multiple input variables. The model can be used to advise cocoa farmers on the estimated processing time for cocoa beans to meet the demands of the export market.Item Atomization of fruit juice with fibres as drying aid : nozzle : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemical and Process Engineering at Massey University, Palmerston North, New Zealand(Massey University, 2019) Mohd Rozali, Siti NadjihaSpray drying of fruit juices is desirable as it produces dry powders which extend the shelf-life, reduce storage and transport costs, and produce a free-flowing powder which makes it easier to blend as an ingredient. Commercially, maltodextrin is added to the juices as a drying aid to increase the efficiency of the spray drying process. In this project, pomace fibres were investigated as an alternative drying aid. The main attraction of pomace fibres as a drying aid is the pomace fibres are originally derived from the fruits itself. This study explores the rheological behaviour of juice-fibre suspensions inside the spraying device, specifically the nozzle, to ensure high efficiency powder production by enabling atomization of the mixtures. This study also sought to determine the type of nozzle and operating conditions for efficient atomization of the juice-fibre suspensions inside the spray dryer. Flow-fields inside a nozzle consists of shear and extensional flows. Previous studies on the shear rheology of fibre suspensions revealed the addition of fibres creates a non-Newtonian shear-thinning liquid. The studies on extensional rheology of fibre suspensions, however, were absent. It is widely known the atomization of liquids with both shear and extensional resistances, require additional energy for atomization when compared to Newtonian liquids or viscous non-Newtonian liquids of a similar intrinsic viscosity. In this work, four types of fibres with different aspect ratios were investigated. Some of the significant and notable methods achieved during the study include 1) the use of capillary viscometer to examine the shear rheology of fibre suspensions at shear rates up to 20 000 s⁻¹, which represents the calculated shear rate experienced during atomization, 2) the building of a portable capillary breakup extensional rheometer to accurately characterize the extensional rheology of the fibre suspensions at high extensional strain rates and 3) the use of flash photography technique to capture the atomization patterns. Important findings from this work include: • Fibre suspension is a non-Newtonian shear thinning liquid with shear viscosity dependents on the fibre aspect ratio. The shear thinning behaviour continued until the shear rate of 25 000 s⁻¹ and a plateau occurred at 25 000 s⁻¹ shear rate. The plateau is independent of the fibre aspect ratio. • The fibre suspension exhibited extensional resistance. The extensional rheological properties of the fibre suspensions were dependent on fibre aspect ratio. When comparing between the shear and extensional rheology of a specific fibre suspension, the transient extensional viscosity, 𝜂⁺𝐸 of the fibre suspension was relatively greater than its corresponding shear viscosity. • The entrance pressure drop into the nozzle was significantly increased with the addition of fibre. This made the use of a pressure nozzle inefficient. It was advised by personal discussion with industry experts that rotary atomizers usually fail in atomizing extensional liquids, so its application was not explored in this study. • Spray visualization showed the extensional resistance of the fibre suspensions significantly affected the atomization behaviour and pattern (droplet size distribution) by forming filament structures connecting successive droplets together. This pattern was absent in Newtonian atomization. • Successful atomization of fibre suspensions was achieved by using a two-fluid nozzle at high atomizing air velocities and at air-to-liquid ratio above 0.25. At an atomizing air velocity of 150 m/s, the atomization performance is dependent on the fibre aspect ratio, but this effect was reduced at higher atomizing air velocities. At the highest tested atomizing air velocity of 240 m/s, all fibre suspensions yielded a volume-based average droplet size, D(v,50), of 200 – 250 µm. • Using a two-fluid nozzle at high atomizing air velocities, the droplets sizes of the fibre suspensions insignificantly reduced when the temperature of the inlet fibre suspensions was increased. No change was observed to the atomization performance when an ultrasonic mechanism was added to the two-fluid nozzle as an attempt to improve the atomization performance. • A method of predicting the atomization performance of a given two-fluid nozzle from its dimensionless numbers, for actual spray dryer applications, was demonstrated and the results showed that the two-fluid nozzle can be used inside a spray dryer if the air-to-liquid ratio exceeds 0.25. Overall, the methodology used in this thesis provides a systemic means of investigating the suitability of an atomization method for the spraying of a non-Newtonian fluid with extensional rheological properties.Item Prediction of the glass transition temperature of fruit juice powders : a thesis presented in partial fulfilment of the requirements for the degree of Doctor in Philosophy in Process Engineering at Massey University, Manawatu, New Zealand(Massey University, 2019) Linnenkugel, SebastianTo overcome the limited shelf life of fresh fruit juice, manufacture aim to reduce the juice to a powdered form that can be available all year around. One technique of powder formulation is the use of spray dryer. However fruit juices are rich in fruit sugars and organic acids, which make them difficult to spray dry. Their low glass transition temperatures lead to stickiness problems in the spray dryer. This work investigates the prediction of the glass transition temperature (Tg) of fruit juice powders and mixtures including high molecular weight components often used as drying aids of their mixtures. The ability to predict glass transition temperatures enables optimization of powder formulations and spray dryer operation to avoid sticking problems. A semi-empirical model is presented to predict the glass transition temperature of fruit juice powders on the basis of the chemical composition and the Tg values of the individual pure components. The Flory-Huggins Free Volume theory is used to describe the relation between the water activity of the powders and the glass transition temperature based on the composition of the powders. These prediction models were tested for different freeze dried multicomponent systems and validated against the glass transition temperatures measured by Differential Scanning Calorimetry (DSC). The model was then applied to predict the Tg of values freeze dried juice and vegetable powders prepared from commercial juice concentrate. The six fruit and vegetable juice powders exhibited higher measured Tg values at zero water activity those that predicted from the model. The 6-14˚C difference between the measured and predicted Tg values cannot be explained purely by the main sugar and organic acid components, but are rather linked to the presence of residual breakdown products of pectins and other polysaccharides from the base fruit. For several powders, a second glass transition temperature was visible in the DSC thermogram, which can be attributed to these additional components. The prediction of the glass transition temperature of the pure juice powders at various water activities showed better agreement with the experimental data the closer the predicted and measured Tg value of the powders was at zero water activity. The Tg values of different low molecular weight components and the polysaccharide maltodextrin DE 9-13 often used as a drying aid was studied. The Tg for the binary and multicomponent systems was well estimated by the prediction model at zero water activity. The addition of higher amounts of maltodextrin DE 9-13 up to a weight fraction of 0.7 in the mixture resulted in a widening of the transition observed in the DSC thermogram, which can be attributed to dynamic heterogeneity of the samples due to the dynamic response times of different domains in the solid matrix. This could be demonstrated by annealing the samples below their glass transition temperatures for 16 hours. The analytical semi-empirical model proved to be a viable method for predicting the glass transition temperature of mixtures of low and high molecular mixtures. Multicomponent systems consisting of more than one high molecular weight component in the form of various soluble polysaccharides and the monosaccharide glucose were investigated for their Tg values at zero water activity. The different mixtures of the low molecular weight components and polysaccharides showed a shift in the glass transition temperature that depended strongly on the Tg value of the pure polysaccharide. However, the overall trend of Tg values for the mixtures of low and high molecular weight components was found to be similar for all mixtures. The Tg values of all systems with various polysaccharides were well predicted. It also highlighted that a weight fraction of above 0.5 for the polysaccharides with a degree of polymerization of sugar units above 5 is necessary in the solid matrix to have a significant impact on the glass transition temperature. Salts were tested as an alternative drying aid to high molecular weight components at various ratios to the monosaccharide glucose. The salts increased the glass transition temperature of the blends at lower concentrations. A weight fraction of 0.2 of salts in the system has the same effect on the Tg values as a 0.5 weight fraction of a higher molecular weight component. The difference in necessary amount to increase Tg can be attributed to the different mechanisms of salts and polysaccharide in the solid matrix. To demonstrate the utility of the model, it was applied to optimize the spray drying of blackcurrant juice concentrate, with the aid of maltodextrin DE 9-13. It has been reported that sticking can be avoided during drying if the operating temperature does not exceed T=Tg + 25˚C. By combining the prediction of the Tg of the solid mixture at various water activities and a mass and energy balance over the spray dryer, reasonable feed composition and operational conditions were found. This allowed the successful conversion of blackcurrant juice into a powder in a single trial without relying on trial-and-error approaches.Item Directional amorphous lactose crystallization : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Bioprocess Engineering at Massey University, Manawatu, New Zealand(Massey University, 2018) Ibell-Pasley, NicholasIt was proposed that during industrial drying of lactose crystals a surface layer of amorphous lactose may be formed in a flash drier and then crystallized during fluid bed drying. This crystallization is hypothesized to occur in one of two directions depending on the conditions, inside-out resulting in a dry product, and outside-in trapping moisture. In the inside-out case the moisture is driven outside the product, in the outside in case this moisture would be contained by a surface layer of crystalline lactose The trapped moisture from the outside-in case is proposed to slowly diffuse through the crystal layer during storage and cause handling problems, explaining observed differences between industrial products. To investigate this scenario the crystallization of amorphous lactose was modelled, and crystallization trials were conducted to try and achieve inside-out and outside-in crystallization. William-Landel-Ferry (WLF) and Arrhenius type kinetics were found to fit literature data for amorphous crystallization. Predictions made using these models showed that amorphous lactose crystallization under the high temperature conditions in a fluid bed dryer was possible. A method for isolating the enthalpy change associated with crystallization of amorphous lactose from simultaneous thermal analysis data was developed. This method shows promise for observing the crystallization process, but it may not be suitable for amorphous lactose quantification. Two methods were designed to achieve inside-out and outside-in crystallization of amorphous lactose. This required the temperature and water activity conditions to be precisely and independently controlled in lab trials. Simultaneous thermal analysis was used to monitor the crystallization of amorphous lactose samples under these conditions. Following the simultaneous thermal analysis, the samples were monitored for moisture release. Both the inside-out and outside-in crystallized samples were observed to slowly release moisture, increasing the measured relative humidity above the expected equilibrium value. Afterwards the samples were analysed and found to still contain low levels of amorphous lactose. The source of the rise in relative humidity could not be definitively attributed to either trapped moisture or ongoing crystallization but would not be expected had crystallization not been induced. Based on these findings it is recommended that a lactose crystal fluid bed drier is operated at conditions which would not allow for amorphous lactose crystallization. These conditions could be determined using the kinetic models fitted here.Item Stabilisation of dried Lactobacillus rhamnosus against temperature-related storage stresses : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Manawatū, New Zealand(Massey University, 2019) Priour, SarahIn the past few years, research has established a link between gut health and overall health and wellbeing. A diverse microbiome is a major step towards a healthy gut. Probiotics could help by improving the gut microbiome diversity and thus, are being added to a wide range of food products. However, maintaining them in a viable state within these food products is a considerable challenge. In order to increase the shelf-life of probiotics, numerous encapsulation systems have been developed to help protect them. Techniques such as emulsification, coacervation, or drying methods have all been employed with varying levels of success. While the final encapsulated bacteria may have enhanced protection and stability, a range of stresses are imposed on the bacterial cells during the actual encapsulation process, including mechanical, physical and chemical. Drying is the technique that confers the most protection to the probiotics, potentially stabilising them for up to several years. However, water plays a structural role and upon its removal, forces appear between cell components leading to the denaturation of proteins or the phase transition of the phospholipids membrane. Thus, bacterial cells need to be dried in the presence protectants that can prevent detrimental events from occurring and damaging the cells. It is thought that there are three main mechanisms by which protectants will confer superior stability. Firstly, the protective matrix can form a glassy system preventing further chemical reactions from happening, and thus protecting the bacteria. Secondly, if protectants are introduced for a period prior to drying, they can interact with the cellular biomolecules, replacing the structural role of the water, and maintaining the biomolecules in their native state when the water is removed from the system. Finally, the protectants can increase the free energy of water, maintaining it in the vicinity of the biomolecules, so that when the water is removed, the biomolecules are still hydrated and in their native state. Therefore, it is obvious that the role of protectants during the drying step is critical. The question that has remained largely unanswered, however, is how long and under what conditions should the protectants be introduced, and what type of protectants work best? Once the probiotics are successfully dehydrated, storage stresses may impair their stability on the shelf. Among these stresses, high temperatures of the surrounding environment is one that has been well documented to be detrimental to the cells and generally leads to a rapid drop in shelf stability. These temperatures can be experienced not only during the life of the product on the supermarket shelves, but also during transport of these consumables around the globe. The effect of changes in temperature on bacterial cell viability is an area which has not been explored in great depth, and the impact that encapsulation may have on the viability under these conditions even less so. Once again, like in the case of the protectants, the materials used to encapsulate the bacteria will be critical to final stability. Materials such as ‘phase change materials’ (PCM), which can absorb and release heat over different temperature ranges could be the key to protecting bacteria under extreme conditions. The aim of this thesis was thus to stabilise a model probiotic: Lactobacillus rhamnosus HN001 to high temperatures occurring during storage and transport. In order to do so, the study was separated into four principal research questions. Firstly, can a pre-drying step (for example the uptake of protectants) help the stability/viability of the bacteria during storage? Secondly, what are the best protectants for long-term storage of Lb. rhamnosus HN001, and why? Thirdly, is it possible that combinations of the most suitable protectants act in synergy, bringing increased storage stability compared to either protectant on its own? Finally, can the inclusion of PCM in the encapsulation matrix give extra protection to the cells during storage? This question would be of particular significance when examining the effect of the fluctuating temperatures experienced during the transport of the probiotics. The first study, therefore, consisted of establishing a protocol to prepare the cells for drying, by finding the early stationary phase where cells are known to be most stable to stress, and then optimising the exposure of the cells to potentially protective solutions of glucose and sucrose at 4 and 20°C. The uptake of the solutes was explored using HPLC, before drying the cells and evaluating the effect that their uptake had on the shelf-life stability of freeze-dried cells. In order to try and understand any interactions between the intracellular biomolecules and the protectants, the Nano DSC was used. Results showed that when cells were exposed to glucose at 20°C, metabolisation took place, and the longer the exposure, the lower the stability of the cells after drying and over storage. Overall, the study revealed that cells exposed to sucrose at 20°C for 4 hours presented best stability indicating that both the type of protectant, and exposure settings are critical to a successful outcome. The results from the Nano DSC showed that sucrose interacted with some of the cell biomolecules, rendering them more stable. The exposure temperature for the rest of the experiments was thus set at 4°C to avoid metabolisation, and the time was set at one hour so that exposure settings would be adapted for both sugars. In the second part of the study, a range of nine protectants (glucose, fructose, galactose, sucrose, lactose, trehalose, betaine, monosodium glutamate (MSG) and sorbitol) were compared for their ability to stabilise freeze-dried Lb. rhamnosus at 30°C for 6 months. Inulin was used as a carrier. The impact of galactose, sucrose, betaine, MSG and sorbitol was studied using a Nano DSC to again try and establish links between biomolecule interaction and stability during storage. Interestingly, MSG led to the best stability overall with a cell loss of 0.19 /month, even though it had the highest water activity of all the samples following freeze-drying. This is contradictory to general thought on how water activity affects bacterial cell stability, with higher water activity generally resulting in increased cell death over time. It was shown, using the Nano DSC, that MSG interacted with most of the cell biomolecules rendering them more stable. MSG was thus selected for further study. Three additional protectants were selected (galactose, sucrose and sorbitol) to look for potential synergistic effects with MSG in terms of protecting the bacteria during storage. The study followed a mixture design of experiment (DoE) in order to obtain an optimal protective matrix. The powder structure was also studied at this point by microscopy along with analysis using the DSC to try and comprehend the importance of the powder structure on the stability of the dried cells. Multivariate analysis was used to link all factors and their relative impact on the cell death rate together. Interestingly, it was found that neither a high glass transition temperature (Tg) nor a low water activity helped to stabilise the bacteria. Instead, the amount of MSG was clearly shown to improve the shelf-life, and a synergy was found between sorbitol and MSG. Microscopy showed that this powder led to a unique structure that most likely collapsed during drying resulting in the shrinkage of the cake and the loss of the porous structure, thus lowering the exposure of the bacteria to oxygen. In addition, a small amount of the sorbitol present in the matrix seemed to help in stabilising additional biomolecules as shown by the Nano DSC. The slowest death rate results obtained were 0.04 /month when MSG alone was mixed with inulin, but the model predicted an even lower death rate due to the synergy occurring between MSG and sorbitol. Finally, this optimised stabilisation matrix was used to study the impact of further protection, in the form of an encapsulate containing a PCM, on the stability of the bacteria. Powders with two different structures were compared using freeze-drying and spray drying techniques. The viability of the resulting powders was assessed during two separate storage studies designed to test the cells against fluctuating temperatures (20 to 50°C) and at constant temperature (35°C). The results showed that PCM appeared to have little impact on the overall stability of the powder. However, it was confirmed that a dense and smooth powder structure helped to maintain the bacteria in a viable state for a longer time than a more porous structure. This was most likely due to the lower surface-area ratio decreasing the exposure with the environment and preventing detrimental reaction such as oxidation. The bacteria in the optimised stabilisation matrix had the best stability, with a death rate of 0.07 /month at 35°C and 0.18 /month under fluctuating temperature from 20 to 50°C. In conclusion, it was found that the interaction of the protectants with cells is of paramount importance in maintaining the cells in a dried, viable state for longer periods at elevated temperatures. In addition, the structure of the powder should also be considered as one of the main mechanisms for protecting the bacteria, as it has a substantial impact on the shelf-life of the powder. Conversely, in this body of work it was shown that a high glass temperature did not enhance, or indeed help to maintain cell viability as has been suggested by many previous studies. A dense structure is, however, believed to protect the bacteria through preventing exchanges with the environment, especially with oxygen. If future work is to be done, it should follow the oxidation of the cells during storage and link it with measures of the powder porosity to gain further insight into the impact of the structure on oxidation stress.Item Performance evaluation of a prototype flat-bed grain dryer : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Postharvest Technology at Massey University(Massey University, 1999) Meas, PysethThe performance of a new prototype flat-bed grain dryer designed for experimental research was evaluated using yellow dent maize grain of two hybrids ("Clint" and "Raissa" which are hard and soft, respectively) in three separate experiments. In experiment I, grain samples at three initial moisture contents (approx. 20, 25 and 30% w.b.) were dried at three air temperatures (58, 80 and 110°C). Dryer performance parameters such as drying time, drying rate, capacity, efficiencies and energy consumption were determined and the dried grain quality attributes were also evaluated. A thin layer drying model for predicting dried grain moisture ratio was proposed. In experiments II and III, grain samples were dried at 80°C air temperature from 25% to 14.5% moisture content, cooled or tempered before assessment of grain quality attributes. Overall, the dryer performance was good in terms of its operation and effects on quality of dried grain. Both dryer operational performance and dried grain physico-mechanical properties were affected by drying air temperature, grain initial moisture content, and the post-drying treatments. Low initial grain moisture content and high drying temperatures increased dryer capacity and reduced total energy consumption for drying. However, both high drying air temperature and high initial grain moisture content increased the incidence of grain damage. Slow cooling and/or tempering of the dried grain increased grain bulk density and reduced breakage susceptibility, especially when cooled or tempered in an airtight and well insulated container. However, these two post-drying treatments did not affect grain hardness significantly. Finally, a conceptual model for evaluating and optimising the performance of mechanical grain dryer is proposed.Item The effects of drying methods and storage conditions on pea seed (Pisum sativum L.) quality and the relationship between high temperature drying and maize seed (Zea mays L.) stress cracks : this thesis presented in fulfilment of the requirements for the degree of Master of Applied Science (Agricultural Engineering) in the Institute of Technology and Engineering, Massey University, New Zealand(Massey University, 1998) Thuy, Nguyen XuanHigh temperature and high relative humidity adversely affect the quality of seeds, and are features of tropical climate. Seed drying and storage are being used increasingly in developing countries to improve seed storage and quality. This study was undertaken to evaluate a range of seed drying methods and storage conditions with the view to selecting an appropriate method(s) for use in tropical countries. Pea (Pisum sativum L.) seeds at three initial seed moisture content (m.c.) of 23.8, 18.0 and 14.5% were dried to 10% seed m.c. before storage. The performances of four different drying methods: artificial dryer (Kiwi Mini) set at 30°C or 45°C, natural sun drying, and in-bin natural ventilation drying were evaluated. Natural sun drying, and in-bin natural ventilation drying were conducted from March to May, 1997, when mean temperature and relative humidity during sunny days were 17°C and 60% respectively. The dried seeds were stored under two conditions: open storage at 20.5°0 and 55% relative humidity (r.h.), and closed storage at 25°C and 90% r.h. for 20, 40, and 60 days. Time and energy consumed for drying by the different methods were determined to compare the drying efficiency when combined with quality of the seed. Deterioration of the seed due to storage conditions and drying methods used was determined by assessing their effects on seed germination, abnormal seedlings, dead seed, hollow heart percentages, and conductivity. Seed samples dried by the Kiwi Mini dryer set at 45°C took 7 hours and those set at 30°C took 17 hours. It took 54 hours with natural in-bin ventilation drying, while sun drying took 37 hours. However, energy consumed when drying seeds at 30°C was 17 kWh, which was more than twice that at 45°C. Seed germination was not significantly different between drying methods, but averaged only 75% because of sprouting damage of the crop prior to harvest. Germinations after open and closed storage for 20 days did not differ, although some differences appeared after 40 days of storage. However, open and closed storage for 60 days significantly reduced seed germination to 54 and 33% respectively. Because seeds are heat-sensitive, drying air temperature and drying rate are particularly important to avoid internal seed breakage, cracking and splitting, fungal growth, and loss of germination and vigour. Selected studies have shown that seed can be dried at high temperature for a short time, followed by tempering to re-distribute moisture and temperature inside the seed, thus reducing the percentage of cracking. Thus, a second experiment was conducted with maize (Zea mays L) to study the impact on seed viability of high temperature drying followed by tempering. Maize at 28.5% initial seed m.c. was dried at 60°C for short periods of 5, 10, 15, 20, or 25 minutes, followed by tempering for 45 minutes at either 30°C or 21°C. This cycle was repeated until maize seeds were dried to 13.0% m.c.. The percentage of cracked seeds, germination immediately after drying, and after an accelerated ageing test, did not differ between 30°C and 21°C tempering. Drying exposure times of up to 10 minutes per cycle at 60°C caused vertical cracks in up to 50% of seeds, but seed germination remained over 90% and seed vigour was also maintained. The percentage of seeds with stress cracks due to high temperature drying (5 - 25 minute cycles) at 60°C followed by tempering had polynomial relationships with seed germination and vigour. Seeds dried at the same temperature without tempering had their germination reduced from 99 to 20%.Item Factors affecting the continued use of the mobile flash dryers by farmer co-operatives, Nueva Ecija, Philippines : a thesis submitted in partial fulfilment of the requirements for the degree Master of Applied Science (Agricultural Systems Management), Massey University, Palmerston North, New Zealand(Massey University, 1999) Rodriguez, Amelita CHarvest of the Philippines second and larger rice crop occurs during the end of the wet season. For members of the rice industry this wet season harvest poses a problem: grain cannot be dried reliably using traditional sundrying methods. Poor drying results in quality reductions and hence farmers receive lower returns. To address this situation the Philippines Government introduced locally manufactured mechanical dryers. This study was undertaken to examine variables which enhance or limit the continued use of the mobile flash dryers in farmers' co-operatives in Nueva Ecija, the Philippines. Two case studies, each consisting of three farmers' co-operatives were investigated using semi-structured interviews. One case comprised co-operatives that continue to use the dryer while the other comprised those that have stopped using it. Results showed that a combination of factors influenced the adoption decisions of the co-operatives. Economic factors, especially the volume of rice handled by the co-operative appeared to be most important. Furthermore, the way that the dryer fitted with the other postharvest systems in the co-operatives was a determinant of adoption decisions. In particular, the co-operatives with rice milling operations or with inadequate alternative drying options utilised the mechanical dryers. The leadership and management of the co- operative appeared also to be a factor. These results indicate that both organisational factors and the characteristics of a technology need to be considered in the development and extension of innovation. Overall the results of this work support the individual and organisational adoption literature. Further work could explore this issue on a wider basis across more co-operatives within the region and across more regions in the country. Key words: Technology adoption, co-operatives, mechanical grain dryer.