Principal research interest is dairy biochemistry with particular reference to the cheese ripening process and includes the following:
Proteolysis and lipolysis in cheese during ripening. The principal biochemical events that occur in cheese during ripening are proteolysis (i.e., the hydrolysis of the caseins to peptides and free amino acids) and lipolysis (the liberation of fatty acids from triacylglycerides) and these processes are essential for the development of flavour in most cheeses.
Ripening of hybrid and non-Cheddar varieties. There is considerable interest in the Irish dairy industry to lessen our traditional dependence on Cheddar cheese. Research on hybrid cheeses and established European varieties derives from this interest but also has assisted the farmhouse cheese sector which produces many of these cheeses.
Role of the coagulant in proteolysis during cheese ripening. The principal proteolytic agents in most cheeses are enzymes from the rennet used to coagulate the milk which remain trapped in the cheese and the role of chymosin and other enzymes used to coagulate milk is one of our important research interests.
Specificity of proteinases on the caseins. Research on proteolysis in cheese during ripening is at the molecular level and is focussed on the specific peptide bonds cleaved by proteinases during ripening and the identification of the many hundred peptides found in cheese.
Role of non-starter lactic acid bacteria and smear microorganisms. In most hard cheeses, a wild microflora (“non-starter lactic acid bacteria”, principally facultatively heterofermentative lactobacilli) develops during ripening which is uncontrolled and contributes to variability of product quality. The control of NSLAB and their effect on cheese ripening has been amongst our major research interests. In certain cheeses (often referred to as “red smear cheeses”, e.g., Limburger or Tilsit), a complex Gram-positive bacterial flora develops on the surface during ripening.Characterization of microbial enzymes important to cheese ripening. The cheese ripening process is catalyzed by a wide range of enzymes most of which originate from microorganisms. Our group has isolated and characterized many of these enzymes (proteinases, peptidases, amino acid catabolic enzymes) from a number of cheese-related organisms.
Application of chemometrics to data analysis. Since cheese ripening is a complex process, large data sets are easily generated. An active area of research has been to apply multivariate statistical techniques (e.g., principal component analysis and multidimensional scaling) and hierarchical and non-hierarchical cluster analyses to the interpretation of chromatographic and electrophoretic data. This area has been developed in close collaboration with Prof E. Parente, Università degli Studi della Basilicata, Potenza, Italy.
Ingredient cheeses. Much cheese is now used for ingredient applications. Recently, we have worked on factors affecting the physical properties of processed cheese and much work on the pathways for flavour generation in cheese is relevant to the production of cheese flavour ingredients used as dustings on crisps and other savoury food products.
Indigenous enzymes in milk. Together with our colleague, Dr A.L. Kelly, we have been active in the study of some of the approximately 60 enzymes found naturally in milk. In particular, we have studied the proteinase, plasmin, which is a leakage protein from the cow’s blood and a number of enzymes from lysosomes of the somatic cells found in milk and our group discovered the presence in milk of the lysosomal thiol proteinase, cathepsin B.
Collaborative non-dairy projects. Many of the techniques developed for the study of cheese may also be transferred to other fermented foods. Together with colleagues in UCC and in universities in Italy, we have engaged in projects studying sourdough bread, meat and fermented sausages.