Date of Award

1-1-2006

Document Type

Master Thesis

Degree Name

Masters of Science (Research)

Department

Biological and Pharmaceutical Science

First Advisor

Brendan McCarra

Abstract

The intracellular contents of spent yeast can be used to produce flavours and flavour enhancers. However there still remains after this process, a significant quantity of cell wall material, which makes up 20-25% of the dry weight of yeast biomass. A major component of the yeast cell wall is the polysaccharide P-glucan. This project involved the investigation of the extraction and characterisation of p-glucan as well as its evaluation as a functional food ingredient. A preparation of spent yeast p-glucan was obtained from two types of spent yeast species, Saccharomyces cervisiae (brewers yeast) and Kluyveromyces marxianus (dairy yeast) obtained from Beamish and Crawford pic and the Carbery Group respectively. Autolysis of the spent yeasts was characterised by a decrease in pH 6.44-6.25, and an increase in dissolved solids from 3.8-12.46% in the extracellular medium. Chemical analysis of the remaining cell wall showed relatively high carbohydrate content of 81.80-84.17%, and a lower protein content of 9.69-15.23%. An alkaline and acetic acid extraction was used to extract p-glucans from the cell walls. When p-glucan yield was determined, Saccharomyces cerevisiae exhibited higher P-glucan yields (63.42%) than p-glucan obtained from Kluyveromyces marxianus (52.08%). This included both alkali soluble and insoluble P-glucan. Functionality tests e.g. Viscosity, whippability, and emulsion stabilising capacity indicated that Saccharomyces cerevisiae performed better than Kluyveromyces marxianus. This can be attributed to the fact that Saccharomyces cerevisiae contains more p-glucan than Kluyveromyces marxianus. The above results compared well with those reported in literature. While extensive work has been reported on oat and barley P-glucan, this study shows yeast P-glucans also have potential as a thickener and stabiliser within the food industry. However its performance in food systems still needs to be tested fully.

Access Level

info:eu-repo/semantics/openAccess

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