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Item Lactose smearing in transport lines : a thesis presented in partial fulfilment of the requirements for the degree of Masters in Process Engineering at Massey University(Massey University, 2002) Mcleod, JeremyThe smearing of lactose in pneumatic conveying lines, leads to cakes of lactose building up within the lines. This is an undesirable situation as it leads to reduced throughput, caused by the narrowing of the lines and the increase in downtime required to unblock and clean the pipes. This study was carried out to investigate the causes of smearing and identify solutions to this problem. Impact testing was carried out, to look at the breakage behaviour of lactose. This identified that energy of impact is the main consideration for the breakage of lactose in pneumatic conveying. This is not only the energy contained before impact, but also the way in which the energy is dissipated during contact. The use of rubber proved an effective technique in lowering the amount of breakage, due to its ability to adsorb and disperse the impact energy during contact. Testing was carried out looking at the ability of sliding contact to cause the adhesion of lactose to a surface. The results showed that combination of the frictional forces and the sliding velocity can provide enough energy to cause the lactose to adhere. The conclusion drawn was the same as that for impact testing, with energy being the main consideration in the breakage and adhesion of lactose to surfaces. A link between amorphous lactose formation and the smearing was found, with the build up in the conveying lines having a higher amorphous concentration than was found on the free flowing lactose powder. An attempt to show a change in the amorphous concentration of α-lactose crystals after impact proved unsuccessful, although the use of a polarised microscope showed the formation of amorphous lactose on the impact surface. Calculations looking at the amount of amorphous lactose that would have formed after impact, identified that the concentrations were below the levels measurable using the methods available. Following on from impact testing work, a rubber lined bend was placed in a section of the conveying line at Lactose New Zealand. Monitoring of this bend showed it to be successful in preventing the adhesion of lactose to walls of the conveying pipe. However, there was a small amount of wear observed at the entrance of the bend. This was concluded to be due to a design defect as the rubber was raised above the level of the main line. More testing needs to be done, with a change in design, to allow a conclusion on the applicability of rubber for preventing lactose buildup to be drawn.Item Lactose fouling of ion exchange technology : a thesis presented in partial fulfilment of the requirements for the Masterate of Technology in Process Engineering at Massey University(Massey University, 1999) Smith, Antony CraigCheese whey is an ingredient used in infant formulae manufacture. Before addition, the cheese whey is fully demineralised using Ion Exchange (IE) technology. Investigation of the IE process revealed low lactose yields. The objective of this thesis was to provide an understanding of the mechanism causing these low yields. This understanding may be used to improve these yields during IE processing. Two mechanisms were proposed for the removal of lactose during IE processing namely resin entrapment and lactose mutarotation adsorption. Investigations of the mechanisms were performed with both continuous and batch benchtop methods. Whey, lactose and DMSO/lactose feed solutions were employed with various resins. DMSO/lactose solution experiments were inconclusive in determining the mechanism. Whey and lactose trials revealed lactose adsorption occurred predominantly onto the macroporous anion resin (0.09 g-lactose/g resin) compared with the gel cation resin (0.04 g-lactose/g resin). In comparison the maximum lactose adsorption onto an alternative gel structured anion resin was shown to be 0.05 g-lactose/g resin. Absorption isotherm results were dependent on the supernatant concentration. The majority of lactose adsorbed onto both the macroporous and gel anion resins was recovered with six and three equivalent volumes of water, respectively. The adsorption dependency on the resin structure and supernatant concentration coupled with the recovery of adsorbed lactose with water proved that the resin entrapment mechanism was causing the low lactose yields. In hindsight the DMSO results were also consistent with the resin entrapment mechanism causing the low lactose yields. It is recommended that to reduce lactose losses during IE processing by 43%, gel structured anion resin (A847S) should be coupled in series with the existing gel structured cation resin (C100H). The gel anion resin would also halve the anion water requirements during lactose recovery flushing.Item Native milk fat globule membrane damage : measurement and effect of mechanical factors in milk powder processing operations : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology of Massey University(Massey University, 2005) Downey, MarkThe goal of this work was to measure native milk fat globule membrane (NMFGM) damage in a number of processing operations within the milk powder manufacturing process. Analysis of the literature showed that NMFGM damage was not well understood, particularly as caused by processing operations within factories. Reliable methods of measuring NMFGM damage were not available: current methods had limited scope or were qualitative in nature. In the highly mechanised dairy industry, damage to the NMFGM can lead to serious quality and financial losses owing to consequences such as lipolysis and creaming. The aims of this work were to develop new techniques for measuring NMFGM damage, and to use these in assessing the effects of a number of operations within the milk powder process. The majority of time was spent on developing two new tests, the selective lipolysis (SL1) test and the particle size zoning (PSZ) test. The SL1 test measures a chemical consequence of NMFGM damage, that is the production of free fatty acids (FFAs). The PSZ test measures a physical consequence of NMFGM damage, that is the change in the fat globule size distribution. Controlled experiments were used to measure NMFGM damage in process operations including pumping, agitation, preheating and evaporation. For these operations, variables such as shear, time, temperature, air inclusion and cavitation were investigated. Surveys of two industrial milk powder plants were also conducted. The results showed that the SL1 and PSZ tests were reproducible, sensitive enough to detect NMFGM damage in a number of process operations, and, together, could give a reasonably comprehensive picture of NMFGM damage. The results of pumping and agitation experiments were consistent with previous research, but were more comprehensive. The effects on measured NMFGM damage of the presence of separated fat in foam or as churned fat have hardly been described by previous workers. Results for the effects of preheating and evaporation on NMFGM damage are new, and challenged the findings of previous research. The need to improve the flexibility and practicality of the SL1 and PSZ tests, so they can he used as widely as possible to gain a comprehensive picture of NMFGM damage across many dairy processes, was identified. Studies should be made to connect the results of the particle size zoning and selective lipolysis tests with product quality and process efficiency data from industrial sites.Item Effect of homogenisation on milk fouling in a tubular heat exchanger : a thesis presented in partial fulfilment for the requirements for the degree of Master of Food Engineering, Massey University, Palmerston North, New Zealand(Massey University, 2004) Martinez-Sanchez, MonicaFouling of equipment surfaces in milk processing has been a costly problem for many years. In spite of an increasing body of knowledge of the fouling mechanism, the problem is not fully understood yet. Recent investigations suggest that the role of fat in whole milk fouling seems to be very important. The state and form of the fat globules, processing conditions as well as the orientation of heating surfaces may affect the fouling mechanism. Homogenisation of milk is known to cause disruption of fat globules and prevent creaming. The present work aimed to investigate the effect of homogenisation on the rate of fouling, composition and structure of fouling layers. Homogenised and un-homogenised milk were used as test fluids. Milk was heated from 4°C to 60°C in a plate heat exchanger then to 70°C and 80°C in a double pipe heat exchanger consisted of a horizontal and a vertical tube. The fouling rate in the double pipe heat exchanger was calculated and expressed as the rate of increase of the overall resistance to heat transfer, normalised using the initial heat transfer coefficient at the beginning of the run. Composition analysis of fouling layers was carried out using standard methods of moisture, ash, fat and protein tests. Resistance to deformation analysis was performed using texture tests; coverage measurement was determined by digital image analysis. Within the experimental conditions used in this work, the effect of homogenisation on the fouling rate could not be ascertained conclusively because of large variations in the values obtained but it had a significant effect in the composition of fouling layers. In all experimental runs, the amount of fat in the fouling layer was higher for un-homogenised milk compared to homogenised milk. In fact, the fat contents of fouling layers were found to be very high (between 30%-60% on a dry weight basis), which agrees with observations of other researches in New Zealand. The coverage and thickness of fouling layers were more influenced by the orientation of heated surfaces than by homogenisation. The strength of fouling layers is affected by their thickness, which decreases with increasing milk temperature.Item Surface modifications to increase dairy production run length : a thesis presented in partial fulfilment of the requirements for the degree of Master of Chemical Engineering at Massey University, [Manawatū], New Zealand.(Massey University, 2013) Runwal, SiddharthFouling is the build-up of undesired deposits on surfaces. In the dairy industry, fouling is mainly seen in heat exchangers where dairy fluid is heated or concentrated. It is one of the primary reasons for restricted run length, causing financial losses from downtime, the use of cleaning chemicals and reduced product quality. Fouling is a complex process and is due to number of factors including the properties of the heat transfer surface. A silica based coating is known to alter the surface properties. This study was carried out to investigate the effect of a silica based coating on fouling by whole milk in a falling film evaporator. Seven independent trials were conducted. In each trial, a control run was carried out followed by a full cleaning of the equipment and then either another control run or a coating run with pasteurized milk from the same batch. There was a six hour interval between the start of the control run and start of the coating run. Since prolonged milk storage may have some effect on fouling rate, control-control runs were carried out to see the effect of prolonged storage. The results obtained from control-control runs were used in analysing the effect of the coating on fouling rate. All coating trials showed consistently lower fouling rate as compared with corresponding control trials. The Pearson’s correlation coefficient of 0.83 showed a strong effect of coating on the fouling rate. Further, a regression analysis gave a p-value of 0.033, indicating that, at the 96.7% level of confidence, coating reduced the fouling rate. The extent of reduction in fouling rate varied from trial to trial. It was estimated that the coating had the potential to increase the run length by a maximum of 34% under the conditions these experiments were carried out.Item Development and application of a model for estimating the efficiency and carbon footprint of refrigeration systems by considering the impact of fouling on condenser performance : a thesis presented for fulfillment of the requirements for the degree of Master of Philosophy in Energy Management at Massey University, Palmerston North, New Zealand(Massey University, 2011) Milgate, Stephen M.Refrigeration systems on industrial plants such as dairy processing facilities are major consumers of energy. The higher the efficiency of these systems the lower the cost of electricity and subsequent carbon emissions from electricity produced from fossil fuels. Traditionally chemical treatment of cooling loops for refrigeration systems has been undertaken in a reactive manner. The treatment regime is only changed when there is a detrimental effect on the system such as the development of corrosion, scale or biofilm. Often this results in medium to long term losses in efficiency before the situation is rectified. A predictive model has been developed that has the potential to allow real time control of chemical treatment for cooling loops. The model predicts the film thickness for common fouling materials found in cooling systems and the heat transfer efficiency losses associated with this fouling. Such a predictive model can be used in conjunction with monitoring of the apparent heat transfer efficiency to infer the film thickness and therefore guide chemical treatment programmes. The model was tested against foulant efficiency relationships published by Qureshi and Zubair, Macleod - Smith and The Carrier Refrigeration Handbook. In all three cases the predictive model produced results that agreed with the results for each of these sources. The model was also tested using the reticulated ammonia refrigeration system at Fonterra Whareroa. Psychrometric, climatic, data logged temperatures and sensor data from the Whareroa system database were used to calculate the efficiency of one of the refrigeration system’s condensers (EC1). Resulting heat of rejection values and an estimated thermal conduction constant (k) based on a deposit analysis were used as inputs for the model to calculate the predicted foulant film thickness. Inspection of the evaporative condenser during the June 2010 shut determined the model had predicted the foulant film thickness to within 6% of the measured 1.62mm. An energy balance was completed on the reticulated ammonia refrigeration system at Whareroa to provide a better understanding of the system dynamics. Unfortunately it was not possible to obtain complete agreement between heat load and heat of rejection for the ammonia system – the level of agreement ranged from 8.9 to 30.2%. This variability seems to be explained by incomplete monitoring of the condenser fan speed. Although the predictive model produced results that agreed with three other researchers the level of efficiency determined by the model is dependent on the accuracy of a number of variables including the thermal conductivity value (k-value) chosen for the foulant material creating the insulating film on the evaporative condenser coils. This is easy to determine for a pure compound but there is no model available to predict the thermal conductivity of a composite fouling material. Consequently this would be one improvement that could be made to the model in the future. Model capabilities would also be enhanced by incorporating the commercial version of EES. This would allow the model to be automated for ‘on-line’ real time system monitoring. The evaporative condensers at Fonterra Whareroa that were used for this study are ‘base load’ heat of rejection units, i.e. they are always fully loaded or turned off. Consequently it is recommended that the model is further tested on refrigeration systems with variable loads to determine the accuracy for partial load situations, and also on systems with a range of fouling materials.Item Microfiltration membrane fouling by dairy proteins : thesis submitted for the degree of Doctor of Philosophy at Massey University, New Zealand(Massey University, 1994) Marshall, Allen D.Microfiltration membrane fouling occurs through the deposition of proteins both on the membrane surface and within the membrane pores. Fouling is complex with both the nature and location of fouling dependent upon the properties of the feed material, the properties of the membrane material and the operating conditions used. Two aspects of fouling have been investigated, one in which the feed contained proteins considerably larger than the membrane pores (casein micelles) and the other, in which the protein (β-lactoglobulin) was much smaller than the pores. In this way, it was possible to separately investigate surface layer formation and fouling within the membrane pores. It has been demonstrated that a casein "gel layer" forms on the membrane surface causing severe fouling during the microfiltration of skim milk on a 0.1 μm polysulphone membrane if the combination of cross-flow velocity and permeate flux leads to a concentration of casein at the membrane wall equal to or higher than that required for "gel layer" formation. Once formed, the gel layer restricts the passage of protein through the membrane and reduces plant throughput. During the microfiltration of β-lactoglobulin on a 0.1 μm zirconium oxide membrane, in the presence of calcium and with high fluxes, protein-protein interactions at or near the pore entrance lead to pore narrowing and the eventual retention of protein by the membrane. High localised shear rates at the pore entrance lead to partial unfolding of the protein and calcium appears to form an ion-bridge between exposed negatively charged protein groups leading to aggregation and multi-layer deposition on the membrane pore walls. The removal of calcium or a reduction in the permeate flux prevents severe fouling and greater than 90% transmission of protein can be achieved. The importance of understanding the properties of the feed material in interpreting and explaining membrane fouling is stressed.Item Heat transfer and fouling in film evaporators with rotating surfaces : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University(Massey University, 1997) Chen, Hong; Chen, HongA study was made on the heat transfer and fouling in thin film evaporators with rotating surfaces. Both theoretical and experimental studies were carried out, in order to gain a better understanding of these evaporators and their design principles, so that this type of evaporator could be effectively used in an on-farm milk evaporation system. By using Nusselt-type assumptions, a theoretical model, which was used to predict the liquid film thickness and heat transfer coefficients on the rotating cone, was developed. The theoretical equations obtained revealed basic relationships between the variables and provided a fundamental knowledge of the liquid flow and heat transfer in the film evaporators with rotating surfaces. The experimental studies on heat transfer were conducted on a Centritherm evaporator, which is available commercially (40° half cone angle), a specially made cone evaporator (10° half cone angle) and a falling film evaporator with a rotating tube. Variables evaluated were the rotating speed, the cone angle, the feed flow rate, the evaporating temperature, the temperature difference between the steam condensing and the liquid evaporating temperatures, and sugar concentration when sugar solution was used. The experimentally measured overall heat transfer coefficients were compared with the theoretical values. It was found that the measured overall heat transfer coefficients increased with increase of the cone rotating speed, and with the rise of the liquid evaporating temperature. The feed flow rate was found to have a more significant effect on the measured overall heat transfer coefficients in the falling film evaporator with a rotating tube than that in the Centritherm and the cone evaporators. The overall heat transfer coefficients decreased with increase of the concentration of sugar solutions, mainly due to the increase of liquid viscosity. It was also found that the measured overall heat transfer coefficients in the Centritherm evaporator increased with an increase in temperature difference up to 30K (for water, 10% sugar solution and skim milk) and then decreased (for water and 10% sugar solution). The formation of bubbles on the evaporating surface at high temperature differences was likely to be cause of this effect. Increase of the cone angle resulted in thinner liquid films and higher heat transfer coefficients. This was reflected in the following experimental results: the measured overall heat transfer coefficients in the falling film evaporator with a rotating tube were slightly lower than those measured in the cone evaporator, but much lower than those obtained in the Centritherm evaporator. The experimental results showed that rotating the tube of a falling film evaporator increased the overall heat transfer coefficient but the increase obtained was very dependent on feed flow rate, and was not sufficient to justify the use of this evaporator in the industry. With the Centritherm evaporator, good agreement between theoretical and experimental overall heat transfer coefficients as a function of the cone rotating speed was obtained by using water. The theoretical model, however, does not adequately describe the whole evaporation process at conditions other than those assumed in the model, which are: laminar liquid film flow, and heat transfer by conduction through the liquid film. It is suggested that waves existing in the liquid film at high Reynolds numbers, and bubble formation on the heating surface at high temperature difference, are the major reasons for the discrepancy between theoretical and experimental results. For the fouling study, the Centritherm evaporator was mainly employed, and three liquid systems: reconstituted skim milk, reconstituted whey solutions and sweet cheese whey solution, were selected. It was found that no fouling was detected after 6 hours' operation in the Centritherm evaporator when reconstituted skim milk and reconstituted whey solutions were used. This indicates that the aggregated whey proteins, which are formed in the manufacture of skim milk powder and whey powder, are less active in inducing fouling. For this reason, only the sweet cheese whey solution was used in further studies. It was confirmed that fouling is strongly linked with the liquid evaporating temperature and the temperature difference between steam condensing and liquid evaporating temperatures. In general, the higher the evaporating temperature and the temperature difference, the faster the deposition rate and the greater the fouling on the surface. It was found that 72% Bovine Serum Albumins (BSA) denatured after running the evaporator, at a evaporating temperature of 70°C and a temperature difference of 20K, for 6 hours. Though the content of BSA in whey solution is small, the denatured BSA could be easily attached to the surface. By association with other depositable materials existing in the whey solution, the thin layer of deposit could reduce the heat transfer coefficients significantly. This was attributed to the lower thermal conductivity of the deposited layer. Fouling was also found to be a function of the liquid velocity. This effect was more significant at lower evaporation temperatures. Increasing the rotating velocity would delay the formation of an initial layer and reduce the rate of fouling. It was also found that there was an induction period in the fouling curves when the evaporating temperature was 60°C. The induction period was reduced when new whey solutions were introduced into the evaporator. It proved the fact that depositable materials are much more easily adsorbed on fouled or unclean surfaces than on clean surfaces. The increase of fouling rate when new whey solutions were introduced suggested that the concentration of activated molecules in the solutions strongly affected the fouling process. A possible mechanism of whey fouling on the rotating surface was proposed. During this study, an attempt was made to develop a new type of evaporator in which a vapour compressor would be integrated with the rotating surface. This was unsuccessful due to the failure of compressing the vapour. Concerning the on-farm evaporation system, which requires an evaporator with high efficiency, compact, and minimum heat load to milk, it is suggested that a rotating surface evaporator with the top cone angle close to 90° (like a disk evaporator) would be optimum and worth to explore.