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Subject: search.filters.subject.Ultrafiltration

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    Fractionation of milk proteins from skim milk using microfiltration : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University
    (Massey University, 1994) Shen, Jian
    The possibility of fractionation of milk proteins from skim milk using microfiltration (MF) was investigated in this project. Pilot scale ultrafiltration/microfiltration equipment (Koch model) was used. Three available MF membranes, 600, 601 and 603, with pore sizes of 1.99μ, 0.85μ and 0.17μ, respectively, were evaluated. The most suitable membrane was found to be MF 603. By microfiltration to concentration factor (CFc) 7, permeation of 46% non-casein nitrogen (NCN) was achieved in contrast to 1% for casein. Using diafiltration with deionised water to a CF 567, permeation of 80% NCN occurred. Therefore, it is possible to obtain a casein-enriched fraction from the MF retentate and a non-casein nitrogen enriched fraction from the permeate by the MF process using MF membrane 603.
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    Evaluation and development of chemical solutions for membrane cleaning in the dairy industry : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Science at Massey University
    (Massey University, 1999) D'Souza, Nisha Maria
    Membranes must be cleaned regularly to remove organic material deposited on the surface from the food or biological fluids processed. Cleaning is a compulsory step in maintaining the permeability and selectivity of the membrane and is also necessary to return the plant to its original capacity, to avoid bacteriological contamination, and to produce products with a long shelf-life. Without cleaning, the flux of solution through the membrane would decline to uneconomic levels. Caustic, acidic and enzymatic based cleaners may be used for membrane cleaning. Such cleaners affect the lifetime and performance of a membrane and should thus be surface-active, soluble, rinsable, non-corrosive, safe, effective and easy to use. The primary objective of work carried out was to evaluate a range of cleaning chemicals and cleaning regimes on a pilot-scale. Cleaning regimes employing conventional caustic and acidic cleaners, and enzymatic detergents have been evaluated for a Desal ultrafiltration membrane. The membrane was reproducibly fouled during the processing of skim milk and skim milk concentrate on a pilot-scale plant supplied by Tuchenhagen (N.Z.) Limited and compared favourably with an industrial plant. A spiral wound membrane of polyethersulfone with an active area of 7.4 m and a 10,000 molecular weight cut-off was selected. A transmembrane pressure of 2.5 bar, a retentate flow rate of 60%, a temperature of 18.5°C, and a recirculation flow rate of 7 m was kept constant during filtration. A combination of flux recovery after cleaning and solute resistance removal was used to assess cleaning performance. Higher flux recoveries (87.3-93.6%) were achieved with surfactant based formulations compared with enzymatic detergents. This was attributed to the wetting action of surfactants which when used in conjunction with a high strength blended alkali solution, aided the convective cleaning solution flow through the membrane pores. Enzymatic cleaning was found to be milder to the membrane. While the enzyme-sanitiser regime yielded good flux recoveries (68.4-87.3%), the enzyme-acid and acid-enzyme regimes were not capable of restoring membrane permeability, resulting in low flux recoveries 64.2-78.9%. The acid in these regimes caused the membrane pores to shrink, restricting the ability of the enzymatic detergent or rinse water to penetrate the foulant and remove it. Based on these results, a new formulation (DR292) with more surfactant action was developed and evaluated. Flux recovery using this new formulation increased by 3.5%. Regimes incorporating non-ionic surfactants and high strength alkali solutions were found to successfully restore membrane permeability because a higher level of surfactant was obtained from the mixture. Further experiments using enzyme-acid and acid-enzyme regimes, and the new formulation need to be trialed on new membranes to determine their long-term effect on membrane permeability and selectivity.
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    A study of some aspects of the quality and yield of cheddar cheese made from milk concentrated by ultraflitration : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in the Department of Food Technology at Massey University
    (Massey University, 1986) Iyer, Mani
    Ultrafiltration (UF) is a concentration and separation process which operates at the molecular level. It has been successfully applied to certain soft cheese varieties with the primary advantage of increased yields. When applied to Cheddar, which is a hard variety, problems are encountered. These are lack of flavour and texture development, lack of economically viable yield increase and practical problems in handling of UF curd. An investigation was undertaken to study the application of UF technology to the manufacture of Cheddar cheese. The emphasis was on the biochemical and biophysical problems in UF Cheddar and the possible yield advantages in making the product. Results suggest that UF per se does not contribute to problems in the quality of UF Cheddar. No major problems were encountered in the cheese making process or in final cheese quality when cheese was made from 2:1 UF retentate using conventional method and equipment. There were, however, no yield advantages. When 3:1 and 5:1 retentates were used, some modification in the method of manufacture, particularly in the cutting time and cutting device, was necessary. The quality of cheese obtained from 3 : 1 retentate was found to be inferior while that from 5:1 retentate was comparable with respect to the control cheeses. The biochemical and biophysical problems associated with the quality of UF Cheddar could be overcome to a large extent by adjusting the amount of starter and rennet added on the basis of quantity of milk prior to UF. This yields Cheddar of normal one-day pH but with residual rennet concentration much higher than that in the conventional product. The higher level is probably required to over come the 'dilution' effect of the extra whey proteins present in the UF product. This 'dilution 'effect may be partly due to the difficulty of rennet diffusion in UF Cheddar and partly a result of a decrease in concentration of flavour compounds due to the presence of extra whey proteins. The results show that subs tanti a l savings i n rennet are not possible in cheesemaking from 5:1 UF retentate. The results also suggest that it is possible to make UF Cheddar with a required residual rennet concentration by regulating the amount of rennet added to the retentate and draining the whey at a predetermined pH. The yield advantage in cheesemaking from 5:1 retentate (if UF Cheddar is made to normal MNFS of 53.5%) was limited to 4% largely because only one third of the whey proteins of UF milk was retained in the cheese. Theoretical analysis of mass balance data indicated that this yield advantage could be improved to about 6% by reducing 'fines' losses and to about 8% by decreasing fatlosses as compared with the conventional process. Given the current state of UF cheesemaking technology, it is possible that reductions in losses in conventional cheese-making plants may prove to be a more profitable method of increasing yields of Cheddar cheese than the use of UF cheesemaking methods.