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)
| Identifer | oai:union.ndltd.org:ADTP/204262 |
| Date | January 2007 |
| Creators | Anjani, Kavya, University of Western Sydney, College of Health and Science, Centre for Plant and Food Science |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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