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Title: Maximising nutritional and flavour qualities of pork sausages
Author: Plotkowiak, Margarethe
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2012
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Both lipid oxidation and the Maillard reaction have been researched extensively. There has been a multitude of books, reviews and publications dealing with the details and products of either reaction. Both are key contributors to the formation of flavour and aromas of cooked foods. However, while many compounds are formed that are desirable, some compounds have been found formed by both reactions which are possibly detrimental to human health. In 2002, it emerged that acrylamide has been found in foods. As acrylamide is a potent toxin, a lot of research has been done in the last years to determine its origin and also how much of it is present in different foods types. Since its discovery it has been determined that acrylamide indeed is formed during the cooking process at high temperatures as an undesired side product of the Maillard reaction. Similarly, a side product of both Maillard reaction and lipid oxidation, Nϵ-carboxymethyllysine (CML), can be formed during advanced lipid oxidation and advance glycation. This compound is a marker for a group of compounds that has been linked with diseases such as renal diseases and Alzheimer's. The aim of this project was to determine how changes in the originating reactions, i.e. Maillard reaction and lipid oxidation, would impact the formation of both desired and undesired products. However, the objective was not only to learn how both compounds could be successfully reduced in a food product but also how the changes to induce these reductions would impact sensory qualities. To help answer these questions, a system was selected which was as close as possible to an actual food product and where changes could be introduced easily. Pork sausages were chosen as a common and popular food which was easily produced and manipulated. This Thesis first describes experiments to evaluate the impact of the composition (meat, fat, rusk, water and seasoning) and cooking on analyses for acrylamide and CML as well as sensory properties and. volatile compounds. These sausages were also compared to commercial samples for all analyses. Secondly, the effect of two antioxidants, one water- and one lipid-soluble, at two concentrations, raw and cooked, on CML, volatiles compounds and sensory properties were compared. Both experiments, change in composition and impact of antioxidants, showed interesting results. In the first experiment, the sensory evaluation showed that preference of consumers lay with samples that were high in fat and rusk but low in meat. The preferred samples were closest to the commercially available ones. Conversely, it was those samples containing high rusk that also showed some acrylamide. However, even at the highest levels measured (25ug/kg), acrylamide from sausages poses no threat to human health. Composition has a tremendous effect on the formation of CML. It appears that low levels of rusk result in higher initial levels of CML but that high levels of . protein result in lower levels of CML following the cooking process. The measured levels of CML (l0mg/kg - 35mg/kg) compare to the reported quantities of CML found in bread, meat or sausages, However, there is not yet a consensus upon whether or not dietary intake of CML is detrimental so no recommendation can be made if the levels of CML found in the experimental and commercial sausages are safe to consume. In the second experiment, two different types of antioxidants at two concentrations were incorporated during the manufacturing process into the recipes of selected experimental groups of the first experiment. The incorporation of antioxidants successfully reduced the formation of CML with varying effectiveness as different groups (high meat/ low meat, high fat/Iow fat and high rusk/Iow rusk) responded differently. Samples containing more water responded best to the water- soluble antioxidant with the biggest reduction of CML, whereas samples containing more fat or rusk showed only very little or no reduction of CML. While more work needs to be performed to fully confirm and understand these effects, the initial results indicate that antioxidants can be used as an effective way of reducing CML in foods. The antioxidant activity in the sample was also tested using colorimetric assays and while samples of the first experiment showed only very little activity the activity of the samples containing antioxidants from the second experiment even at a low level surpassed the activity measured in the commercial samples. The sensory trials showed that samples with added rosemary extract or green tea extract at low levels showed no difference to the in the sensory acceptability whereas samples containing green tea at a higher level had the lowest acceptance. Overall, the main impact on flavour is the composition of the ingredients fat, rusk and meat with the preference towards high fat and high rusk samples. On the other hand, the formation of the undesired side product CML can be improved through the introduction of antioxidants whereas acrylamide, albeit predominantly formed in the preferred high rusk/ high fat samples does not pose a threat to human health in the first place so further reduction is not necessary.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available