• Identification of the key compounds responsible for Cheddar cheese flavour

      Beresford, 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.
    • Influence of Enterococci and Thermophilic Starter Bacteria on Cheddar Cheese Flavour

      Beresford, Tom; Cogan, Tim; Wallace, J.; Drinan, D.; Tobin, S.; Piveteau, P.; Carroll, N.; Deasy, B. (Teagasc, 1998-09-01)
      This project set out to identify suitable enterococci and thermophilic starter strains which could be added to the cheese during manufacture (as starter adjuncts) with the specific aims of enhancing flavour during ripening as well as facilitating flavour diversity - a trait sought by many commercial Cheddar companies. This project confirmed the potential of thermophilic lactic acid strains to affect flavour when used as starter adjuncts in Cheddar cheese manufacture. Their use can also lead to the development of novel flavours. Many adjunct cultures proposed to-date to enhance Cheddar flavour are composed of strains of lactococcal starter, selected for their flavouring capacity. However, application of such strains in industry would lead to increased probability of phage attack on the primary starter. On the other hand, thermophilic lactic acid strains are phage unrelated to conventional starter and thus would not lead to the introduction of starter specific phage into the cheese plant. A thermophilic strain from the Moorepark collection (DPC 4571) was shown to have major commercial potential as a flavour enhancer.