No description available.

No description available.

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)

Graduation date: 1992

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Please read the abstract in the front section of this document / Dissertation (M Inst Agrar (Food processing))--University of Pretoria, 2005. / Food Science / unrestricted

Attempts were made to adapt the microtiter hemagglutination inhibition assay technique for the assay of enterotoxin A. The presence of a potent hemagglutinin in crude and partially purified preparations and the instability of sensitized erythrocytes prevented its use for routine analysis of enterotoxin from culture media and foods. A capillary tube immunological assay was developed in which 1 μ g of enterotoxin/ml was detected in less than 1 hr . Interfacial reaction of antisera and enterotoxin solutions in a 1 mm internal diameter capillary tube allowed rapid detection and serological typing of enterotoxins. Staphylococcus aureus growth and enterotoxin A development in Cheddar cheese slurry was evaluated. S. aureus growth and enterotoxin production occurred at 32 C. in 45 and 60% moisture cheese slurries following inoculation with 10 3 to 10 5 bacteria/gram. Hydrogen peroxide (0. 5%) treatment of slurry at 37 C did not inhibit S. aureus and enterotoxin A development. Heating slurry at 72 C for 30 min eliminated staphylococci but reinoculation with ripening organisms was essential. Addition of sorbic acid (0. 2 to 0. 3%) to a slurry adjusted to pH 5. 0 with lactic acid, inhibited staphylococci. in milk and slurry. Cheese flavor development was retarded due to inhibition of micrococci and lipolysis. Non-protein nitrogen increases paralleled that of sorbate-free controls. Sorbate treatment was preferred over other treatments .

The objective of this study was to evaluate the effects of using food grade coatings and nettings formulated with xanthan gum and propylene glycol (PG) or carrageenan (CG), propylene glycol alginate and PG on aged Cheddar cheese to control Tyrophagus putrescentiae growth at temperatures of 10°C, 15°C, and 20°C and relative humidity’s of 75% and 85%. Cheddar cheese cubes with treated nets and coatings inhibited mite growth at all temperature and relative humidity combinations. Control cheese cubes either without coatings or in untreated nets had fewer mites (P<0.05) at 10°C than at 15°C or 20°C. The sensory properties of the cheese were not affected by the coatings and nettings at 10°C and 75 % RH. However, all other temperature and RH combinations with the exception of the CG netting at 15°C at 75 % and 85 % RH caused sensory flavor differences (P<0.05).

No description available.

No description available.