To optimize conditions to prepare a good quality of enzyme-modified cheese (EMC), EMC samples were prepared by using combinations of Neutrase RTM/Lactobacillus casei enzymes, Neutrase RTM/Debitrase(TM), NeutraseRTM/Flavorzyme(TM) and NeutraseRTM/PalataseRTM. Based on the results obtained from sensory and RP-HPLC analysis, the optimal combinations to prepare a good quality of EMC were found to be: NeutraseRTM with (I) L. casei enzymes (aminopeptidase activity 86.4 LAPU/g and esterase activity 110.0 U/g), (II) Debitrase(TM) (aminopeptidase activity 22.0 LAPU/g), (III) Flavorzyme(TM) (aminopeptidase activity 6.5 LAPU/g), and (IV) PalataseRTM M (lipase activity 200 LU/g). / The water-soluble fractions of EMCs prepared with different enzyme combinations were subjected to RP-HPLC on a Delta Pack C18 column, and selected peaks were purified on the same column using a binary gradient. One peak from NeutraseRTM digest, five peaks from NeutraseRTM /Debitrase(TM) digest, and two peaks from NeutraseRTM /L. casei enzyme digest were purified and identified by API mass spectrometry. All the purified peptides contained active sites within their sequences. / The volatile compounds in a series of EMCs prepared by L. casei and commercial enzymes as well as Cheddar cheese (mild, old, extra old) were also identified by using Pyrolysis/GC/MS and dynamic headspace techniques. Overall, 5 ketones, 8 fatty acids, 3 alcohols and 2 aldehydes were detected in most of the samples using Py/GC/MS. Propanoic, hexanoic, octanoic, decanoic, dodecanoic and tetradecanoic acids were found to be the major fatty acids present in EMC prepared by L. casei enzymes. Dynamic headspace analysis revealed the presence of 17 compounds including fatty acids, ketones, alcohols, aldehydes, and hydrocarbon in most of the sample analyzed. The flavor of EMC seems to depend not on any particular key component, but rather on a critical balance of all components present.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.21562 |
| Date | January 1999 |
| Creators | Haileselassie, Seble Sereke Berhan. |
| Contributors | Lee, B. H. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Food Science and Agricultural Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001657428, proquestno: MQ50782, Theses scanned by UMI/ProQuest. |
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