Commercial flavour-enhancing enzymes were delivered in an encapsulated form to accelerate Cheddar cheese ripening. Polymers such as alginate, chitosan and k- Carrageenan were screened to be used as encapsulant material for microencapsulation of the commercial protease enzyme, Flavourzyme®. Alginate was found to be a suitable polymer for Flavourzyme encapsulation using the Inotech® encapsulator while _-Carrageenan and chitosan were too viscous for extrusion through the encapsulator nozzle. Gelling of alginate-Flavourzyme microcapsules in 0.1M CaCl2 resulted in poor encapsulation efficiency (ranging 17- 18% depending on the alginate concentration). Incorporation of Hi-Maize™ starch or pectin as filler materials into the alginate-Flavourzyme encapsulation matrix to increase encapsulation efficiency by minimising porosity also resulted in poor encapsulation efficiency. An alternative approach to the modification of the cationic gelling solution, by adding chitosan, significantly increased the encapsulation efficiency to 70-88% and produced mostly spherical capsules with an average diameter of 500_m. Encapsulation efficiency increased with an increase in chitosan concentration from 0.1 to 0.3% (w/v) in the cationic gelling solution of 0.1M CaCl2. Though gelling of alginate-Flavourzyme microcapsules in gelling solution of 0.1M CaCl2 containing 0.3% (w/v) chitosan resulted in higher encapsulation efficiency, a chitosan concentration of 0.1% (w/v) was chosen for further work as higher concentrations of chitosan in the gelling solution resulted in aggregation of capsules during formation. Gelling time of 10 min and alginate concentrations in the range 1.6 to 2.0% (w/v) were found to be optimal encapsulation parameters for Flavourzyme encapsulation while 2.0% (w/v) solution of trisodium citrate was found to be optimal for in vitro release of encapsulated enzymes for measurement of enzyme activity. Flavourzyme capsules stored frozen or freeze-dried were shelf stable for at least 10 weeks retaining about 80% of the initial enzyme activity as opposed to retention of 25-34% activity in air-dried capsules. Leakage of encapsulated Flavourzyme prepared from 1.6% (w/v) alginate was slightly higher than those prepared from 1.8 and 2.0% (w/v) alginate in cheese milk. Flavourzyme-alginate capsules prepared from 1.6, 1.8 and 2.0% (w/v) alginate retained over 70% of the initial enzyme activity under simulated cheese-press pressure. Concentration of alginate had no significant effect (p > 0.05) on the retention of encapsulated Flavourzyme when the capsules were pressed for 4h; however when the simulated cheese press duration increased to 8 and 16h the retention of encapsulated Flavourzyme was significantly higher (p [less than] 0.01) in capsules produced from 2.0% (w/v) alginate. Incorporation of encapsulated enzymes into the milk prior to rennetting resulted in an even distribution of capsules in the cheese matrix compared to aggregation of capsules, when added to milled curd prior to salting. All cheeses; control with no added enzymes and experimental cheeses with free and encapsulated Flavourzyme and/or Palatase showed higher levels of moisture and lower levels of fat compared to standard Cheddar cheese due to the variation in the manufacturing protocol. There was no significant difference (p > 0.05) in fat and final pH between control and experimental cheeses and there was no difference in the numbers of coliforms, E.coli, Salmonella, Listeria, coagulase positive staphylococci, Bacillus cereus, yeast and moulds in control or experimental cheeses. Increased and prolonged proteolysis was observed in cheeses with encapsulated Flavourzyme showing increased release of several peptides, also with the formation of new peptides absent in the control cheese with no added enzymes. Accumulation of high molecular weight/hydrophobic peptides was higher in cheeses with free Flavourzyme followed by cheeses with encapsulated Flavourzyme. Concentration of water-soluble peptides increased with the increase in the concentration of encapsulated Flavourzyme in the cheese. Concentration of water-insoluble peptides was higher in control cheese compared to cheeses with encapsulated Flavourzyme even after 180 days ripening. After 30 days of ripening, concentration of most free amino acids was about 3 times greater in cheeses with encapsulated Flavourzyme than in control and about 7 times higher after 90 days ripening. Concentration of total amino acids was consistently higher in cheeses with encapsulated Flavourzyme compared to control. Cheese grading scores for body, texture and appearance of all cheeses with encapsulated enzymes were lower than control and free enzyme treated cheeses during the entire grading period of about 100 days due to crumbly and pasty texture. Control and cheeses with added Flavourzyme received high overall score for flavour. Flavour score of cheese with encapsulated Flavourzyme at a concentration of 0.75 LAPU/g milk protein was higher than all cheeses around 50 days with better overall flavour score until about 94 days ripening with improved flavour and elimination of bitterness. However the flavour of enzyme treated cheeses deteriorated with time and the control cheese scored the highest for flavour. Though increased concentration of free fatty acids was detected in cheeses treated with encapsulated lipase; Palatase, these cheeses developed rancid, unpleasant, strong lipolytic flavours as early as 55 days ripening. / Doctor of Philosophy (PhD)

$ beta$-Galactosidase (E.C. 3.2.1.23) or lactase was produced by the growth of a selected Bacillus subtilis strain (KL88) which was adapted to grow at 10$ sp circ$C. The growth and enzyme production were maximal at 2% (w/v) lactose supplemented with 0.2% (w/v) yeast extract. A Fast Protein Liquid Chromatography system (FPLC) was used for $ beta$-galactosidase purification. The enzyme was purified to 44-fold over the crude extract with a recovery of $ sim$54%. Native-PAGE and SDS-PAGE using "PhastSystem" showed the presence of two isoenzymes having molecular weights of 88 and 170 kD. The purified enzyme showed high activity at low temperatures (10$ sp circ$C) and recorded an optimum pH of 7.0. The K$ sb{ rm m}$ values were found to be 2.21 mM and 28.08 mM for o-nitrophenyl-$ beta$-D-galactopyranoside (ONPG) and lactose, respectively. / $ beta$-Galactosidase from psychrotrophic Bacillus subtilis was specific to the $ beta$-D-glycosidic linkage normally present in lactose. / To investigate the possibility of producing proteinase-free $ beta$-galactosidase from this psychrotrophic microorganism, FPLC was used for the rapid separation of $ beta$-galactosidase.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 6, 2007 Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. Includes bibliographical references.

Thesis (Masters)--Linköping Institute of Technology, 1989. / "January 1990." Includes bibliographical references (leaves 53-55).

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: This study describes: the evaluation of the current, and potential assay methods for the quantification of cholesterol, cholesteryl esters and free fatty acids in milk and the application thereof ; an account of the difficulties associated with the usage of FoodPro® Cleanline, an enzyme preparation used as processing aid, during ultra-high temperature processing of milk ; the development of activity assays which can be used for the kinetic characterization of glycerophospholipid cholesterol acyltransferase, the active enzyme in FoodPro® Cleanline ; the development of an accurate and facile activity assay, and the validation thereof, which can be used for the validation of enzyme activity prior to dosage of milk with FoodPro® Cleanline. / AFRIKAANSE OPSOMMING: Hierdie studie beskryf: die evaluering van die huidige, en potensiële, metodes vir die kwantifisering van cholesterol, cholesteriel esters en vryvetsure in melk, sowel as die toepassing van hieridie metodes ; 'n verduideliking van die moeilikhede wat ondervind word gedurende die gebruik van FoodPro® Cleanline, 'n ensiempreparaat vir gebruik as 'n verwerkingshulpmiddel, tydens ultrahoë-temperatuurprosessering van melk ; die ontwikkeling van aktiwiteitsbepalings metodes vir gebruik in kinetiese karakterisering van gliserofosfolipied cholesterol asieltransferase, die aktiewe ensiem in FoodPro® Cleanline ; die ontwikkeling van 'n akkurate, eenvoudige aktiwiteitsbepalings metode, en bevestiging van hierdie metode, wat gebruik kan word vir kwalitieitskontrole alvorens die dosering van melk met FoodPro® Cleanline.

Thesis (M.S.)--California Polytechnic State University, 2009. / Title from PDF title page; viewed on Apr. 21, 2009. "March 2009." "In partial fulfillment of the requirements for the degree of Master of Science in Agriculture." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: Phil Tong, Ph.D. Includes bibliographical references (p. 102-103). Also available on microfiche.

In food processing, inadequate surface sanitation procedures lead to the formation of biofilms in which bacteria attach and aggregate in a hydrated polymeric matrix of their own synthesis. Formation of these sessile communities and their inherent resistance to existing sanitation procedures and agents are at the root of the risk of bacterial infections for consumers. Due to this existing problem, an effective method for reducing biofilm formation in dairy processing equipment is necessary for dairy products processing. Ultraviolet Pulsed light Technology has shown a positive effect in eliminating microorganism populations on food products. The objective of this work is to evaluate the effect of Pulsed light Technology on a biofilm of different dairy component matrices (e.g. Water (control); whey protein isolates (WPI), lactose, and sweet whey). This evaluation will be performed using the three strains of spore forming Bacillus species most common in commercial milk powder (B. subtilis, B. coagulans, and B. licheniformis). The matrix in which the evaluation was made consisted on allowing the attachment of endospores to on to a square 2.5cm x 2.5cm ASI 304 stainless steel coupon. Four Xenon light treatment levels (no treatment, 5 bursts, 10 seconds, 20 seconds and 30 seconds) were applied to the coupon surfaces using the Xenon model RC847 machine. The attachment of Bacillus to stainless steel in water as matrix was 1000 to 3000/ sq cm as measured in our laboratory. Results showed that there was a significant difference in spore reduction depending on the matrix of the biofilm and with the intensity of the Xenon treatment. Reduction in spores ranged from 1 to 4.7 logarithmic reduction cycles depending on the material of the biofilm, the strain of spores and the intensity of treatment. We conclude that there is significant potential to use this technology in maintaining low spore counts in commercial dairy powders.

This body of work investigates various techniques for the surface modification of food contact materials for use in food packaging and processing applications. Nanoscale changes to the surface of polymeric food packaging materials enables changes in adhesion, wettability, printability, chemical functionality, and bioactivity, while maintaining desirable bulk properties. Polymer surface modification is used in applications such as antimicrobial or non-fouling materials, biosensors, and active packaging. Non-migratory active packagings, in which bioactive components are tethered to the package, offer the potential to reduce the need for additives in food products while maintaining safety and quality. A challenge in developing non-migratory active packaging materials is the loss of biomolecular activity that can occur when biomolecules are immobilized. Polyethylene glycol (PEG), a biocompatible polymer, is grafted from the surface of ozone treated low-density polyethylene (LDPE) resulting in a surface functionalized polyethylene to which a range of amine-terminated bioactive molecules can be immobilized. The grafting of PEG onto the surface of polymer packaging films is accomplished by free radical graft polymerization, and to covalently link an amine-terminated molecule to the PEG tether, demonstrating that amine-terminated bioactive compounds (such as peptides, enzymes, and some antimicrobials) can be immobilized onto PEG-grafted LDPE in the development of non-migratory active packaging. Fouling on food contact surfaces during food processing has a significant impact on operating efficiency and can promote biofilm development. Processing raw milk on plate heat exchangers results in significant fouling of proteins as well as minerals, and is exacerbated by the wall heating effect. An electroless nickel coating is co-deposited with polytetrafluoroethylene onto stainless steel to test its ability to resist fouling on a pilot plant scale plate heat exchanger. Further work was performed to test the stability of non-fouling material after extended exposure to an alkali detergent or acid sanitizer formulated for clean-in-place procedures in dairy processing facilities. Additionally, the anti-corrosive property of the surface coating was tested on carbon steel against chlorine ions, a common corrosive agent found in the food industry. Accelerated corrosion and long-term chemical exposure studies were conducted to measure the coating stability against the harsh corrosive agents.

I. Introduction. II. Production of Sanitary Milk. III. Milk as a Disease Distributor. IV. Pasteurization of Milk. V. Methods of Bacterial Count. VI. Intensive Study of Desirable and Undesirable Bacteriain Milk. VII. Conclusion. VIII. References / M.S.