This thesis presents several Raman spectroscopic studies of bovine milk-derived products (skim and whole milk powder, anhydrous milk fat, processed cheese and soy cheese made from milk protein). Raman spectroscopy, unlike infrared spectroscopy (both mid- and near-infrared), has not been widely used as an analytical tool within the dairy industry. The purpose of this project was to assess the utility of Raman spectroscopy in several dairy industry relevant problems. FT-Raman spectroscopy coupled with partial least squares (PLS) reliably predicted the concentration of fat and protein within whole milk and protein within skim milk powders as evidenced by ratios of prediction to deviation in excess of three. It was shown that sample geometry did not significantly affect the calculated predictive models, thereby allowing the simplest, quickest method of sample presentation to be utilised without harming quantification model efficacy.
The fat fraction of milk was further investigated, and it was shown that Raman spectra collected from anhydrous milk fat samples were a good basis for solid fat content (SFC) determination. Such spectra were collected when the samples were held at 40 �C, pretreated by baselining and area normalisation, and analysed using PLS with modified jack-knifing (PLS1-JK). Triacylglycerol class concentrations were also well predicted by PLS1-JK models developed from Raman spectroscopic data. Resonance enhancement of β-carotene within fat was shown to have little effect on the reliability of the optimal prediction model when compared to SFC Raman quantification.
Raman microscopic mapping for heterogeneity description of processed cheese and soy cheese mimics was examined. The FT-Raman milk powder constituents study had shown fat and protein Raman spectra within complex dairy mixtures could be distinguished, hence this utility was applied to mapping of cheese systems. Univariate, principal components analysis and multivariate curve resolution methods of analyses were compared; as expected the more complex samples required multivariate methods of analyses. Raman microscopic mapping was not a time efficient method in comparison to the standard method of confocal laser scanning microscopy. However, Raman spectroscopic mapping is a more universal technique which allowed the presence of an unexpected localised constituent within the soy cheese mimics to be observed. It was proposed that this constituent was a crystalline form of a short saturated fatty acid.
| Identifer | oai:union.ndltd.org:ADTP/202527 |
| Date | January 2008 |
| Creators | McGoverin, Cushla Maree, n/a |
| Publisher | University of Otago. Department of Chemistry |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Cushla Maree McGoverin |
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