Browsing Food Programme End of Project Reports by Author "Aherne, Seamus"
Identification of the key compounds responsible for Cheddar cheese flavourBeresford, Tom; Wallace, J.; Aherne, Seamus; Drinan, Finbarr; Eason, D.; Corcoran, M.O.; Mulholland, E.; Hannon, John A. (Teagasc, 2000-09-01)There is a poor understanding of the relationship between organoleptic assessment of cheese and quantitative analysis of flavour compounds. Further, the contribution of particular cheese-making parameters such as ripening temperature and starter culture has not been fully elucidated. During the ripening of most cheese varieties complex chemical conversions occur within the cheese matrix. In most cheese varieties breakdown of protein is the most important flavour development pathway. The primary cheese protein, casein, is degraded enzymatically to short peptides and free amino acids. The agents primarily responsible for these conversions are the residual rennet that is retained in the cheese curd at the end of the manufacturing phase and the proteinases and peptidases that are associated with the starter bacteria. While the rate and degree of proteolysis are of vital significance for desired flavour development, the direct products of proteolysis do not fully define cheese flavour. Much research is now demonstrating that the further biochemical and chemical conversions of the products of proteolysis, in particular the amino acids, are necessary for full flavour development. The products produced by these pathways are volatile at low boiling points and are thus released during mastication of the cheese in the mouth. Many of these volatile compounds contribute to the flavour sensation experienced by the consumer. A very wide spectrum of such compounds have been isolated from cheese, in excess of two hundred in some cheese varieties. It is now generally accepted that there is no individual compound which defines cheese flavour completely and that the flavour sensation is the result of numerous compounds present in the correct proportions. This has become known as the Component Balance Theory . The application of modern analytical techniques as proposed in this project would provide a greater understanding of the significant flavour compounds in Cheddar cheese and help to identify the impact of specific cheese-making parameters such as starter flora and ripening temperature on the production of volatile flavour compounds. This data would assist the general programme on flavour improvement of cheese which should ultimately benefit the cheese manufacturer. Hence this project set out to develop methods to identify the key flavour compounds in Cheddar cheese. These techniques would then be applied to experimental and commercial cheeses during ripening in an effort to identify key compounds and the influence of starter cultures and ripening temperature on their production.
Nutrition: Nutritional Attributes of Animal and Milk Fat (CLA).STANTON, CATHERINE; Lawless, Fergal; Murphy, John; Aherne, Seamus; Devery, Rosaleen; O'Shea, Marianne (Teagasc, 2000-09-01)In the recent past, there has been considerable interest in the potential health-promoting properties of conjugated linoleic acid (CLA), a fatty acid produced naturally in ruminant animals. CLA has been shown to be a very effective anti-cancer agent in animal models and cell culture studies, as well as being capable of retarding the initiation and progression of heart disease (atherosclerosis). It has also been shown to have potential as a growth promoter and is capable of improving feed efficiency. Hence from a human health viewpoint, it appears desirable to increase CLA levels in foods to protect against disease and enhance general health and well-being. The primary sources of CLA are animal fats (including dairy fats) derived from ruminant animals while vegetable fats and oils contain significantly lower levels. This project was aimed at enriching the CLA content of dairy foods through animal dietary manipulation, and milk fat fractionation.